chemistry new edition

["8.40 Chapter 8 PbS + 4H2O2 \u2192 PbSO4 + 4H2O thermal conductor due to its rigid three-dimen- sional structure, in which carbon atoms are closely Black White and regularly arranged. Diamond is a not good electrical conductor as there are no free electrons \t10.\t Thermal conductivity and electrical conductivity in the structure. Graphite on the other hand has of metals are attributed to close packing in met- free electrons in the layer lattice structure which als and the presence of free electrons in the metal makes it a good electrical conductor. Graphite is a lattice respectively. Though diamond and graph- bad thermal conductor. ite are allotropes of carbon, diamond is a good HINTS AND EXPLANATION","91CChhaapptteerr ONrugmanbiec r CShyesmteimstrsy Remember Before beginning this chapter, you should be able to: \u2022\u2002h\u0007ave knowledge of elements, compounds and mixtures. \u2022\u2002\u0007review the placement of elements in periodic table. Key Ideas After completing this chapter, you should be able to: \u2022\u2002\u0007s\u0007tudy the unique features of carbon. \u2022\u2002\u0007understand the classification of organic compounds. \u2022\u2002\u0007use the nomenclature of organic compounds. \u2022\u2002\u0007understand isomerism in organic compounds. \u2022\u2002d\u0007escribe the preparation and properties of simple alkanes, alkenes and alkynes. \u2022\u2002\u0007study about formation of coal and petroleum, isolation of products of distillation of coal and petroleum. F I G U R E 1 . 1 \u2002 Figure Caption","9.2 Chapter 9 INTRODUCTION Organic chemistry is the branch of science which touches almost every aspect of material civilisation today. The age old classification of chemical compounds into two broad categories as organic and inorganic compounds originated on the basis of the conception that they basically differ in their source of origin. Inorganic compounds were supposed to take their origin from mineral kingdom whereas organic compounds were believed to have their origin from plant and animal kingdoms. This concept leads to the assumption of vital force theory according to which the synthesis of organic compounds could be carried out only in the presence of a mysterious vital force available in living systems. The name \u2018organic\u2019 originated from this concept. The accidental synthesis of urea from an organic compound, ammonium cyanate was a major breakthrough in the field of organic chemistry. A German scientist Fredrich Wohler prepared urea, a component of human urine, by heating ammonium sulphate and potassium cyanate. Since then, the development of organic chemistry has proceeded at a tremendous pace. With the advent of synthesis of a large number of organic compounds, the definition of organic chemistry lost its significance. The modified definition of organic chemistry was stated as the chemistry of carbon compounds. This definition stemmed from the basic fact that all the compounds in living systems bearing water invariably contain carbon. However, this definition was considered ambiguous because many inorganic compounds like CO2, CaCO3, etc. containing carbon are available. Later on, the principal characteristic of carbon compounds in living systems is that carbon is essentially associated with hydrogen. This idea paved the way for the precise definition of organic chemistry as the chemistry of hydrocarbons and their derivatives. Though the name \u2018organic\u2019 is slightly misleading in the context of the present status of chemistry, the sharp line of distinction between inorganic and organic compounds continues to remain as such till today. Nevertheless, in the present scenario, the special status of organic chemistry owes not to the source of origin but to the remarkable properties exhibited by the compounds of carbon which\u00a0clearly distinguish them from compounds of the rest of the hundred odd elements in the periodic table. UNIQUE PROPERTIES OF CARBON COMPOUNDS Organic compounds differ from inorganic compounds in most of the general properties. \t1.\t\u0007Number of compounds: The number of organic compounds is much more than that of inorganic compounds. In fact, the organic compounds comprise about 90 per cent of all known compounds. \t2.\tC\u0007 omposition of compounds: Composition of organic compounds is confined to very few elements of the periodic table like carbon, oxygen, hydrogen, nitrogen, halogens and sulphur. In\u00a0 contrast to these, inorganic compounds are composed of almost all the elements in the periodic table. \u0007All these properties distinguish organic compounds from the inorganic compounds. In view of these characteristics, the study of carbon compounds as a separate branch of organic chemistry is justifiable. These properties of organic compounds are due to some special features possessed by carbon. \t1.\t\u0007Tetravalency: Carbon atom has electronic arrangement of 2, 4 which represents the presence of 4 electrons in the valence shell. It requires four more electrons to complete its octet. Therefore, carbon exhibits tetravalency.","Organic Chemistry 9.3 \t 2.\t C\u0007 atenation: Carbon has a remarkable property of forming covalent bonds with other carbon atoms, thus, forming long chains. This ability of forming long chains with atoms of the same element is called catenation. Among all the elements, carbon shows maximum catenation capacity due to the maximum strength of carbon\u2013carbon bonds. This catenation property of carbon accounts for the formation of innumerable number of compounds. C CCC C CCC CC C CC \t3.\tF\u0007 ormation of multiple bonds: Due to its small size, carbon can easily form multiple bonds with carbon, oxygen, nitrogen, etc. This bond multiplicity is also responsible for the formation of a wide variety of carbon compounds. Examples: HH HO H CC H H C C OH H CC H H \t4.\t\u0007Isomerism: The molecules of all organic compounds can be represented by two types of formulae. They are discussed in the following: (a)\u2002\u0007Molecular formula: It indicates the actual number of atoms of various elements present in one molecule of an organic compound. However, it does not give us any idea regarding the type of bonds in the molecule. Example: C2H6 In one molecule of ethane, there are two carbon atoms and six hydrogen atoms. (b)\u2002\u0007Structural formula: It gives the exact arrangement of the atoms of different elements present in the molecule. Example: HH H CCH HH Ethane \t\u0007\u2003 In case of organic compounds, it is quite probable that two or more organic molecules may possess the same molecular formulae but different structural formulae. That means the molecules may differ in the structural arrangement of atoms. This phenomenon is called isomerism. CLASSIFICATION OF HYDROCARBONS Hydrocarbons are a major class of organic compounds which contain only carbon and hydrogen as the constituent elements. Hydrocarbons are broadly classified into two categories on the basis of the skeleton of carbon chain.","9.4 Chapter 9 \t1.\tAliphatic hydrocarbons or Open chain hydrocarbons T\u0007 he hydrocarbons which contain straight chain or branched chain of carbons are called aliphatic hydrocarbons. Examples: HHHH HHH H CCCC H H CCCH H CH2 H H HHH CH 3 Straight chain hydrocarbon Branched chain hydrocarbon \u0007 \u0007Aliphatic hydrocarbons are further classified as saturated and unsaturated hydrocarbons based on the nature of carbon\u2013carbon bonds present in the hydrocarbon molecules. (a)\u2002\u0007Saturated hydrocarbons: In the molecules of saturated hydrocarbons, all the valencies of the carbon atoms are satisfied by single bonds. These are called alkanes. General formula of this class of compounds is CnH2n + 2. Examples: HHH HHHH H CCCH H CCCC H HHH HHHH Propane Butane (b)\u2002\u0007Unsaturated hydrocarbons: The molecules of these hydrocarbons contain one or more carbon-carbon multiple bonds. These are called unsaturated hydrocarbons. Based on the type of multiple bond, unsaturated hydrocarbons are further classified into two categories as discussed hereunder. \u0007Alkenes: The unsaturated hydrocarbons which contain a carbon\u2013carbon double bond in their molecules are called alkenes. General formula of alkenes is CnH2n (assuming that one double bond is present in the molecule) Examples: HH HH HH HH HH HH CC==CC CC HH HH CC == CC HH 11\u2013\u2013PProroppeennee HH EEththeennee \u0007Alkynes: These are unsaturated hydrocarbons which contain a carbon\u2013carbon triple bond in their molecules. General formula of alkynes is CnH2n\u20132 (assuming that one triple bond is present in the molecule). Examples: H H CC C H H CC H 12 3 Ethyne H 1\u2013Propyne","Organic Chemistry 9.5 \t2.\tClosed chain hydrocarbons \u0007The class of hydrocarbons which possess closed chains of carbon skeleton are called closed chain hydrocarbons. On the basis of chemical behaviour, they are further classified into two types, i.e., alicyclic and aromatic hydrocarbons. (a)\u2002\u0007Alicyclic hydrocarbons: These compounds resemble aliphatic hydrocarbons in their chemical characteristics. They contain rings of three or more carbon atoms. HH H C H C C C H HH H H CC H H HH C Cyclopropane H Cyclobutane (b)\u2002\u0007Aromatic hydrocarbons: This class of compounds also contain rings of carbon atoms but differ widely from aliphatic hydrocarbon analogues in their chemical behaviour. They show certain characteristic features which are not shown by aliphatic hydrocarbons. Benzene is the simplest aromatic hydrocarbon. As a matter of fact, benzene is considered the parent hydrocarbon for the entire class of aromatic compounds since all of them essentially possess one or more benzene rings in their structures. H C H H CC CC H CH H Benzene NOMENCLATURE OF HYDROCARBONS Nomenclature implies assigning proper names to the various compounds on the basis of certain criteria. In case of organic compounds, two systems of nomenclature are in use which we now discuss. \t1.\tT\u0007 rivial system: In the earlier period when vital force theory was in effect, the names of organic compounds were given on the basis of the source of origin of the compounds. But with the advancement of synthetic organic chemistry and discovery of enormous number of organic compounds, this system of nomenclature lost its significance. \t 2.\t I\u0007UPAC system: The need for a more systematic method of naming the organic compounds resulted in framing certain rules for nomenclature of organic compounds by IUPAC. (a)\u2002\u0007Longest chain rule: In the given structural formula, the longest possible carbon chain is selected. This carbon chain is called parent carbon chain. Based on the number of carbon atoms in the longest chain, a root word is assigned. The root word for the first four members takes its origin from trivial names. For the other members, Greek numerals are used for giving the root word.","9.6 Chapter 9 TABLE 9.1\u2002 Root words based on the number of carbon atoms in the longest chain Number of carbon atoms Root word present in the longest chain Meth Eth 1 Prop 2 But 3 Pent 4 Hex 5 Hept 6 Oct 7 Non 8 Dec 9 10 Example: CC C C C CC C C Longest chain with seven carbon atoms. Root word corresponding to seven carbons\u2014hept. (b)\u2002\u0007Rule of primary suffix: The extent of saturation or unsaturation in the carbon chain is indicated by primary suffix which is added to the root word. TABLE 9.2\u2002 Primary suffixes based on the nature of compounds Nature of compounds Primary suffixes Saturated (all C\u2212C bonds) \u2212ane Doubled bonded Unsaturated (one C=C bond) \u2212ene Triple bonded Unsaturated (one C\u2261C bond) \u2212yne \u0007In case of unsaturated hydrocarbons, the parent carbon chain selected should include multiple bonds. \u0007It is also essential to mention the position of a multiple bond in the carbon chain. This is done by numbering the carbon chain from one end to the other. The chain is numbered in that direction in which the multiple bonded carbon gets the least number. The position of multiple bonded carbon is mentioned before the root word. Examples: H H HH HH \u2014\u2014 \u2014\u2014C\u2014 1C \u2014 \u2014\u2014 \u2014\u2014 2 \u2014\u2014 \u2014\u2014 H \u2014 6C \u2014 5C \u2014 4C \u2014 3C\u2014 H H HHHHH Root word for 6 carbon chain\u2014hex Primary suffix\u2014ane Name\u2014Hexane","Organic Chemistry 9.7 H H H HH \u2014\u2014 \u2014 \u2014\u2014 \u2014\u2014 \u2014\u2014 H\u2014 C \u2014 C\u2014 C \u2014 C=C 5 43 2 1 HH H H Root word for five carbon chain\u2014pent Primary suffix\u2014ene. Position of double bond\u22121 Name: 1\u2212Pentene HH \u2014\u2014 \u2014\u2014 H\u2014C \u2014 C C \u2014 C \u2014H 4 321 HH Root word for four carbon chain\u2013but primary suffix is \u2013yne Position of triple bond\u22122 Name: 2\u2212Butyne (c)\u2002\u0007Rules of substituents: A univalent group formed after the removal of one hydrogen atom from alkane remains attached to the parent carbon chain. This univalent group is called alkyl group. TABLE 9.3\u2002 Alkyl groups based on parent hydrocarbons Parent hydrocarbons Alkyl groups (formula) Alkyl groups (name) methyl CH4 (methane) \u2013CH3 ethyl C2H6 (ethane) \u2013C2H5 propyl C3H8 (propane) \u2013C3H7 butyl C4H10 (butane) \u2013C4H9 I\u0007n case of branched chain hydrocarbon, these alkyl groups which are linked to the parent carbon chain are considered substituents. The prefix corresponding to the alkyl group is added before the root word by mentioning the position number of the carbon in the main chain which it is attached to. The carbon chain is numbered in that direction in which the carbon linked to the substituent gets the least number. Examples: H H H H HH | | | | || H \u2014 C\u2014 C \u2014 C \u2014C \u2014 C \u2014 C \u2014 H 7 65 4 3 || | || | HH H H 2CH2 | CH 3 1 Root word\u2014hept Prefix\u2014methyl Position of the substituent\u20143 Name\u20143-methyl heptane","\u20149.8 Chapter 9 \u2014\u2014 \u2014 Isomerism When two or more substances have the same molecular formulae but differ in the structural arrangement of atoms within the molecule, they are called isomers and the phenomenon is called isomerism. Since the isomers differ in the structural arrangement of atoms, the phenomenon is called structural isomerism. Depending on the type of variation in carbon chain, the structural isomerism is of different types which we now discuss. Chain Isomerism in Alkanes Long chain alkanes differ in the arrangement of carbon atoms in the chain. Two or more molecules may possess the same molecular formula, but they may differ in the arrangement of carbon atoms in the chain. This type of isomerism exhibited by hydrocarbons is known as chain isomerism and the molecules are called chain isomers. The straight chain isomer is called n-isomer. The isomer with a single branch at a carbon atom is called an iso-isomer. The isomer with two branches on the same carbon atom is called a neoisomer. Examples: \t1.\tButane Molecular formula: C4H10 Chain isomers of butane (\ta)\u2002 H3C \u2014 H2C \u2014 CH2 \u2014 CH3 n\u2013butane CH3 \t(b)\u2002 H3C \u2014 CH \u2014 CH3 Isobutane \t2.\tPentane Molecular formula: C5H12 Chain isomers of pentane \t(a)\u2002 H3C \u2014 CH2 \u2014 CH2 \u2014 CH2 \u2014 CH3 n\u2013pentane CH3 \t(b)\u2002 H3C \u2014 CH2 \u2014 CH \u2014 CH2 \u2014 CH3 Isopentene CH3 \t(c)\u2002 CH3 \u2014 C \u2014 CH3 CH3 Neopentane Position isomerism These isomers have same carbon chain with same number of branches but differ in the position of multiple bond or substituent on the carbon chain.","Organic Chemistry 9.9 Example: Pentene molecular formula: \u2013C5H10 CH3 \u2014 CH2 \u2014 CH2 \u2014 CH = CH2 CH3 \u2014 CH = CH \u2014 CH2 \u2014 CH3 1\u2013Pentane 2\u2013Pentane C3H \u2014 CH \u2014 CH2 \u2014 CH2 \u2014 CH3 H3C \u2014 CH2 \u2014 CH \u2014 CH2 \u2014 CH3 \u2014 \u2014 CH3 CH3 2\u2013Methyl pentane 3\u2013Methyl pentane Thus on rearranging the carbon atoms, different isomers are obtained. These isomers differ largely in physical properties and to some extent in chemical properties. However, the compounds with same constituent elements may possess different molecular formulae but have similar type of bonding and hence show similar chemical properties. These compounds can be arranged into series which gives rise to an idea of homologous series. Functional Isomerism Functional isomerism is the type of isomerism in which the isomers differ with respect to the nature of functional group. Since the functional group is responsible for the chemical properties of organic compounds, the compounds with different functional groups possess different chemical properties. Homologous Series A series of organic compounds in which each member differs from the next by a constant amount when arranged in an increasing order of their molecular weights is called a homologous series. The adjacent members of this series differ by 14 in their molecular weights or \u2013CH2 group, and hence have a general formula. The members show a regular gradation in physical properties and similar chemical properties. Thus, these can be prepared by similar methods. TABLE 9.4\u2002 Homologous series of alkanes (general formula CnH2n + 2) IUPAC names of the alkane Molecular formulae Structural formulae Methane CH4 H \u2014\u2014 H\u2014C \u2014H Ethane C2H6 H HH H\u2014C \u2014 C \u2014H \u2014\u2014 \u2014\u2014 Propane C3H8 HH H HH H\u2014C \u2014 C \u2014 C \u2014H \u2014\u2014 \u2014\u2014 \u2014\u2014 Butane C4H10 H HH H H HH H \u2014C \u2014 C \u2014 C \u2014 C \u2014H \u2014\u2014 \u2014\u2014 \u2014\u2014 \u2014\u2014 Pentane C5H12 H H HH H H HHH H\u2014C \u2014 C \u2014 C \u2014C \u2014C \u2014H \u2014\u2014 \u2014\u2014 \u2014\u2014 \u2014\u2014 \u2014\u2014 H H HHH","9.10 Chapter 9 TABLE 9.5\u2002 Homologous series of alkenes (general formula CnH2n) IUPAC names of the alkene Molecular formulae Structural formulae Ethene C2H4 HH 1\u2013Propene C3H6 H\u2014C = C \u2014H\u2014\u2014\u2014\u2014 \u2014\u2014 \u2014\u2014 \u2014 HHH H\u2014C = C \u2014C \u2014H \u2014\u2014 \u2014 \u2014 1\u2013Butene C4H8 H H H HH \u2014\u2014 \u2014\u2014 H\u2014C \u2014C \u2014C = C\u2014H HH H 1\u2013Pentene C5H10 H H H HH \u2014\u2014 \u2014\u2014 \u2014 H\u2014C \u2014 C \u2014 C \u2014 C =C\u2014H HHH H TABLE 9.6\u2002 Homologous series of alkynes (general formula CnH2n\u20132) IUPAC names of the alkene Molecular formulae Structural formulae Ethene C2H2 H\u2014C \u2261 C \u2014 H 1\u2013Propyne C3H4 H H\u2014C\u2014C \u2261 C\u2014H \u2014\u2014 1\u2013Butyne C4H6 H HH H\u2014C\u2014C \u2014C \u2261 C \u2014 H \u2014\u2014 \u2014\u2014 1\u2013Pentyne C5H8 HH HH H H\u2014C\u2014C \u2014C \u2014C \u2261 C \u2014 H \u2014\u2014 \u2014\u2014 \u2014\u2014 HH H EXAMPLE Give IUPAC names for the following: (i) H3C CH CH2 CH = CH2 (ii) CH3 C CH3 \t CH3 H3C \t\u2002 CH3 (iii)\t C2H5 (iv)\u2002 CH3 HC \u2261 C C CH3 \t H3C CH = CH CH CH3 H","Organic Chemistry 9.11 SOLUTION (ii) \u2002 2, 2-Dimethyl propane (iv)\u2002 4-Methyl-2-pentene (i)\t 4-Methyl-1-pentene\t (iii)\t 3-Methyl-1-pentyne\t EXAMPLE Molecular formula of a hydrocarbon is C5H10. What type of isomerisms are exhibited by it? Give the structural formulae of the isomers. SOLUTION Molecular formula C5H10 corresponds to pentene. It can exhibit position isomerism and chain isomerism. Possible structural formulae are \u2002(i)\tCH2 = CH \u2013 CH2 \u2013 CH2 \u2013 CH3\t \t 1 \u2013 Pentene (ii)\tCH3 \u2013 CH = CH \u2013 CH2 \u2013 CH3 \t 2 \u2013 Pentene\t (iii)\t CH3 H2C = C CH2 CH3 (iv)\t CH3 H2C = CH CH CH3\t (v) CH3 \t H3C C = CH CH3 (i), (ii); (iii), (iv); (iii), (v); (iv), (v) are position isomers (i), (v); (i), (iv); (i), (v); (ii), (iii); (ii), (iv); (ii), (v) are chain isomers EXAMPLE Write the possible isomers for the following molecular formulae. (a)\t C4H8O\u2002\u2002\u2002\u2002\u2002\u2002\u2002\u2002\u2002\u2002\u2002(b)\u2002 C3H6O2\u2002\u2002\u2002\u2002\u2002\u2002\u2002\u2002\u2002\u2002\u2002(c)\u2002 C5H12O SOLUTION (a)\t Molecular formula: C4H8O \t Possible isomers \t (i)\tCH3 \u2013 CH2 \u2013 CH2 \u2013 CHO Butanal CH3 \t (ii)\t H3C CH CHO 2- Methyl butanal","9.12 Chapter 9 O \t (iii)\t CH3 C CH2 CH3 2- Butanone \t\t(i), (iii) functional isomers. \t\t(i), (ii) are chain isomers. (b)\t Molecular formula: C3H6O2 \t Possible isomers \t\u2002(i)\tCH3 \u2013 CH2 \u2013 COOH Propanoic acid \t (ii)\tCH3 \u2013 COOCH3 Methyl ethanoate \t (iii)\tHCOOCH2CH3 Ethyl methanoate \t\t(ii), (iii) are metamers while (i), (ii); (i), (iii) are functional isomers. (c)\t Molecular formula: C5H12O \t Possible isomers: \t\u2002(i)\tH3C \u2013 CH2 \u2013 CH2 \u2013 CH2 \u2013 CH2OH (ii)\t OH \t H3C CH2 CH2 CH CH3 (iii)\t CH3 \t H3C CH2 CH CH2OH (iv)\t CH3 H3C C CH2OH \t\u2009\u2009 CH3 (v)\t OH \t H3C CH2 CH CH2 CH3 \t\u2009(vi)\tH3C \u2013 CH2 \u2013 O \u2013 CH2 \u2013 CH2 \u2013 CH3 \t (vii)\tH3C \u2013 H2C \u2013 H2C \u2013 H2C \u2013 O \u2013 CH3 \t\t(i), (ii); (i), (iii); (i), (iv) are chain isomers \t\t(i), (ii), (v) are position isomers \t\t(i), (vi); (i), (vii) are functional isomers ALKANES Alkanes are aliphatic saturated hydrocarbons represented by the general formula CnH2n+2, where \u2018n\u2019 is the number of carbon atoms. The simplest hydrocarbon is an alkane with one carbon attached to four hydrogen molecules. Methane Methane is the simplest hydrocarbon of the homologous series of alkanes. Trivial names for methane are marsh gas and fire damp.","Organic Chemistry 9.13 Occurrence It is available in the earth\u2019s crust in the form of natural gas as it is the most volatile of all alkanes. Biogas or gobar gas also contains methane a the chief constituent. Laboratory Preparation of Methane Principle: In general, all alkanes can be prepared by the decarboxylation of sodium or potassium salts of corresponding carboxylic acids. Carboxylic acids are a class of organic compounds containing \u2013COOH group where the hydrogen is acidic in nature and can be replaced by sodium or potassium. The reagent used for decarboxylation is soda lime (NaOH + CaO). RCOONa + NaOH \uf8e7\uf8e7(aClkaaO\uf8e7ne)\uf8e7\u2192 R _ H + Na2CO3 Methane can be prepared from the sodium salt of the carboxylic acid containing two carbon atoms. The carboxylic acid containing two carbon atoms is ethanoic acid or acetic acid (CH3COOH), and its sodium salt is (CH3COONa), i.e., sodium acetate. This on treatment with sodalime (NaOH + CaO) gives methane. Sodium acetate Hard glass + Soda lime test tube Methane gas Glass jar Bunsen Iron stand burner Water FIGURE 9.1\u2002 Preparation of methane gas CH3COOH + NaOH+ \u2192 CH3COONa + H2O CH3COONa + NaOH + \uf8e7\uf8e7CaO\uf8e7\u2192 CH4 + Na2CO3 (methane) Process The mixture of sodium acetate and soda lime is heated in a hard glass test tube. Methane gas is evolved and is collected by downward displacement of water. TABLE 9.7\u2002 Physical Properties of Methane Parameters Characteristics Colour Colourless Odour Taste No characteristic smell Solubility Tasteless Vapour density Insoluble in water and soluble in organic solvents like CCl4, alcohol 8 (lighter than air)","9.14 Chapter 9 Chemical Properties of Methane \t1.\t\u0007Combustibility: Methane burns in excess of oxygen to give carbon dioxide and water. This reaction is called combustion and it is an exothermic reaction. It burns with a pale blue flame: CH4 + 2O2 \u2192 CO2 + 2H2O In an inadequate supply of oxygen, methane undergoes incomplete combustion to give carbon monoxide and water: 2CH4 + 3O2 \u2192 2CO + 4H2O \t2.\t\u0007Pyrolysis: On heating methane strongly in the absence of air above 1000\u00b0C, methane undergoes decomposition forming carbon and hydrogen. CH4 \uf8e7>\uf8e7100\uf8e70\u00b0C\uf8e7\u2192 C + 2H2 \u2191 \t3.\t\u0007With steam: In the presence of Al2O3, methane reacts with steam liberating hydrogen and carbon monoxide. CH4 + H2O \uf8e7A\uf8e775l02O\u00b0\uf8e7C3 \u2192 CO + 3H2 \t4.\t\u0007Substitution reactions: Since alkanes are unreactive due to the presence of all C\u2013C single bonds, the characteristic reactions of alkanes are substitution reactions. Example: Halogenation of methane Methane undergoes substitution reaction with chlorine in presence of sunlight. In this reaction, one or more hydrogens are replaced by chlorine to form the corresponding methylhalides: CH4 + Cl2 \uf8e7\uf8e7\u2192 CH3Cl + HCl CH3Cl + Cl2 \uf8e7\uf8e7\u2192 (methyl chloride) CH2Cl2 + Cl2 \uf8e7\uf8e7\u2192 CH Cl3 + Cl2 \uf8e7\uf8e7\u2192 CH2Cl2 + HCl (methylene dichloride) CHCl + HCl (chloroform) CCl4 + HCl (carbon tetrachloride) Structure: Methane molecule has four carbon hydrogen bonds which are arranged tetrahedrally. The shape of the molecule is tetrahedral with a bond angle of 109.5\u00b0. ALKENES AND ALKYNES TABLE 9.8\u2002 Comparative study of alkenes and alkynes Parameters Alkenes Alkynes General formula CnH2n CnH2n \u2013 2 Type of carbon\u2013carbon bond Double bond (C=C) Triple bond (C \u2261 C) Common name Acetylenes Simplest compound Olefins Ethyne (acetylene) Ethene (ehtylene)","Organic Chemistry 9.15 TABLE 9.9\u2002 Comparative study of ethene and ethyne Parameters Ethene Ethyne Molecular formula C2H4 C2H2 Structural formula H\u2014C\u2261C\u2014H HH Trivial name Acetylene H C=C C Ethylene Preparation Method of Ethene Ethene can be prepared by cracking kerosene. Cracking Cracking is the process of breaking up of long chain hydrocarbons into smaller chain hydrocarbons by heating at high temperature in the absence of oxygen. Basically, cracking is an important method of preparing simpler alkanes and alkanes from higher alkanes. Cracking is of two types: \t1.\t\u0007Thermal cracking: The process involves heating the compound to a high temperature in the absence of a catalyst. \t 2.\t Catalytic cracking: The process involves heating the compound in the presence of catalyst. Example: \u0007Long chain alkane with six carbon atoms, i.e., hexane when subjected to cracking gives butane CH3 \u2212 CH2 \u2212 CH2 \u2212 CH2 \u2212 CH2 \u2212 CH3 \uf8e7\uf8e7Heat\uf8e7\u2192 H3C \u2212 CH2 \u2212 CH2 \u2212 CH3 + CH2 = CH2 (Hexane) (Butane) (Ethene) Laboratory Preparation of Ethene In the laboratory ethene can be prepared by heating ethyl alcohol with excess of concentrated sulphuric acid at 180\u00b0C. Apart from ethene, carbon dioxide and sulphur dioxide gases are evolved. These gases are removed by passing the gases over caustic soda. Finally, ethene gas is collected over water by the down ward displacement of water. Thistle funnel Ethene gas (Ethylene gas) Ethanol + Conc. Water Sulphuric acid FIGURE 9.2\u2002 Preparation of ethene C2H5OH \uf8e7C\uf8e7o1n8.\uf8e7H0\u00b02CS\uf8e7O4 \u2192 C2H4 + H2O","9.16 Chapter 9 Laboratory Preparation of Ethyne Ethyne can be prepared in the laboratory by taking a little amount of calcium carbide in a conical flask to which a few drops of water are added. Ethyne gas is evolved and it is collected by downward displacement of water: CaC2 + 2H2O \u2192 HC \u2261 CH + Ca(OH)2 Ethyne Thistle funnel Water Pinch cock Ethyne Calcium carbide + Water FIGURE 9.3\u2002 Preparation of ethyne TABLE 9.10\u2002 Comparative study of ethene and ethyne Ethene Physical properties Colourless, tasteless gas Peculiar odour Ethyne Insoluble in water Colourless, tasteless gas Soluble in non-polar solvents Characteristic garlic odour Vapour density 14 Insoluble in water Slightly lighter than air Soluble in non-polar solvents Vapour density 13 Slightly lighter than air Chemical Properties (i)\u2002Combustion Burns with a pale blue, sooty flame in excess Burns in excess of air with evolution of large amounts of\u00a0air of\u00a0CO2 C2H4 + 3O2 \uf8e7\uf8e7air \u2192 2CO2 + 2H2O 2C2H2 = 5O2 \uf8e7\uf8e7ExAcier\uf8e7ss \u2192 4CO2 + 2H2O","Organic Chemistry 9.17 Chemical Properties Ethene Ethyne (ii)\u2002Hydrogenation When a mixture of ethyne and hydrogen in 1 : 2 ratio When equal volumes of ethane gas and is passed over heated nickel at 300\u00b0C, two molecules of hydrogen is passed over heated nickel or hydrogen get added. Product may be ethene or ethane platinum at 300\u00b0C, one molecule of hydrogen is added HH HH Ni H C=C H \u2013 C = C \u2013 H + H2 Ni H C C HCC H + H2 H+H 2 300\u00b0C Ethyne 300 \u00b0C Ethene HH HH Ethene Ethane 300\u00b0C Ni HH (iii) Addition of bromine HCCH Decolourisation of bromine water takes place || when ethene gas is passed through bromine HH water and one molecule of bromine is added Ethane HH HH Decolourisation of bromine water takes place when ethyne gas is passed through bromine water as two molecules of bromine get added Br Br H C = C H + Br2 H C C H H C C H + Br2 H C = C H 1,2 Dibromoethene Br Br 1,2 \u2013 Dibromoethane HH Br Br H C = C H + Br2 H C C H (iv) Polymerisation Br Br A number of ethene molecules add to each 1,1,2,2 \u2013 Tetabromoethene other at high temperature forming long chains called polythene Three molecules of ethyne add to each other forming benzene nH2C = CH2 \u2192 (CH2 \u2212 CH2 )n 3HC \u2261 CH \uf8e7R\uf8e73e0d0\u00b0\uf8e7hCot\uf8e7\u2192 C6H6 Cu tube Applications of Chemical Properties \t1.\tH\u0007 ydrogenation of unsaturated hydrocarbons: This reaction is made use of in the hydrogenation of vegetable oils. Some vegetable oils containing unsaturation, when subjected to hydrogenation in the presence of a nickel catalyst at 473 K and 5 atm pressure, get solidified and produce vanaspathi ghee. Vegetable oils + H2 \uf8e74\uf8e773K\uf8e7N,i5a\uf8e7tm \u2192 vanaspathi ghee Examples: Groundnut oil, mustard oil, cotton seed oil, etc.","9.18 Chapter 9 \t2.\t\u0007Decolourisation of bromine water: This reaction is used for testing the unsaturation in organic compounds. TABLE 9.11\u2002 Uses of hydrocarbons Compounds Useful product Use Methane Natural gas Bio gas Automobile fuel, fertiliser synthesis Ethene Derivatives Domestic fuel Polythene Synthesis of useful industrial products Ethyne Ethene gas Manufacture of plastics Oxy acetylene Acetylene Artificial ripening of fruits, preparation of thiokol and glycol Welding metals Illumination, ripening of fruits EXAMPLE Methane is considered as a more environment friendly fuel than petrol. Justify. SOLUTION Methane on combustion produces the least amount of CO2 among all hydrocarbons. Petrol contains hydrocarbons ranging from C5 to C10. These hydrocarbons produce more amount of CO2 than methane on combustion. Moreover, the knocking increases with the length of carbon chains. Petrol can show more knocking property which reduces the fuel efficiency and requires more amount of fuel per release of unit energy. Due to these reasons, methane is considered as more environment friendly fuel than petrol. CO2 being a greenhouse gas causes global warming. EXAMPLE Two containers A and B are filled with the same amount of chlorine gas. Limited amount of methane is passed into container \u2018A\u2019 and excess of methane into container \u2018B\u2019. Identify the products formed in A and B. Give reason in support of your answer. SOLUTION If limited amount of methane is passed through the container \u2018A\u2019 methyl chloride is formed first. As the amount of methyl chloride increases, it competes with methane for the available chlorine. Once the concentration of methyl chloride exceeds the concentration of methane, chlorine attacks on methyl chloride rather than methane, forming methylene chloride which in similar way gets chlorinated finally forming CCl4. The end product is a mixture of methane, methyl chloride, methylene chloride, trichloromethane and carbon tetrachloride.","Organic Chemistry 9.19 In second case if excess of methane is passed, only methyl chloride is formed. CH4 + Cl2 \u2013HCl CH3Cl Cl2 CH2Cl2 Cl2 CHCl3 \u2013HCl \u2013HCl Methane + Chlorine Methyl Methylene Trichloro methane chloride chloride \u2013HCl Cl2 CCl4 Carbon tetrachloride CH4 + Cl2 \u00ae HCl + CH3Cl (excess)\t Methyl chloride EXAMPLE A more hydrogenated oil is less rancid than less hydrogenated oil. Give reasons. SOLUTION Rancidity of oils is due to the presence of acids and some other organic compounds. These compounds are formed by the attack of oxygen on the double bonds of unsaturated oils. In the hydrogenated oil, the unsaturation positions are converted to saturated positions. As a result, oxidation of double bonds is prevented. Hydrocarbons, thus, in most cases are useful for the generation of energy. Some of them are available naturally. There are also other natural resources of energy which are widely used. NATURAL SOURCES OF ENERGY Energy is the primary requirement for the existence of life on earth. Solar energy, hydel energy and wind energy are some sources of energy which are inexhaustible. This is because they can be generated continuously and can replace the used up energy from time to time. They are, therefore, called renewable sources of energy. On the other hand, there are some energy sources which get exhausted over a period of time as they can not be replenished from time to time so easily. Coal and petroleum are two major non-renewable sources of energy. These are organic matter and are formed by the degradation of dead plants and animals. Formation Millions of years ago, the dead plants and animals were buried beneath the surface of earth. Owing to the high temperature and pressure existing in the bottom most strata of earth\u2019s crust, the organic matter in the remains of plants got converted to coal while small marine animals and plants got converted into petroleum. Hence, these are called fossil fuels. As this is a very slow process and takes millions of years, coal and petroleum are known as non-renewable sources of energy. Coal and petroleum are complex mixtures of hydrocarbons. Hydrocarbons being combustible, coal and petroleum also undergo combustion producing large amounts of energy. Therefore, they act as sources of energy. These two are not only the major reservoirs of energy which meet 90 per cent of the energy requirements of the world, but also the main sources for the synthesis of many useful organic chemicals.","9.20 Chapter 9 Coal Composition of coal: Coal is mainly composed of carbon and also some hydrocarbons. In addition to these, coal contains some inorganic compounds of nitrogen, oxygen and sulphur. Different varieties of coal which differ in the percentage of carbon are available. TABLE 9.12\u2002 Varieties of coal Variety of coal Percentage of carbon Anthracite 90 per cent Bituminous 70 per cent Lignite 40 per cent Peat 10\u221215 per cent Extraction of coal: The technique used for the extraction of coal from mines depends upon the mode of occurrence of coal in the earth\u2019s crust. Coal, when present in the upper layers, is extracted by open cast mining technology. Coal available in the deeper layers of earth\u2019s crust can be extracted by using underground mining technology. Destructive distillation of coal: When coal is subjected to heating at high temperatures up to 1300\u22121700 K in the absence of air, a number of volatile products are obtained along with a non- volatile residue called coke. The process of heating of coal in the absence of air is called destructive distillation or carbonisation: The volatile products are mainly composed of three components, namely, coal gas, ammonia and coal tar. Isolation of products: The volatile products are first passed through water. Ammonia gets dissolved in water and is removed. Coal tar being insoluble in water, settles down as an oily liquid. Coal gas which is also insoluble in water escapes out. It consists mainly of methane, carbonmonoxide and hydrogen. Fractional Distillation of Coal Tar Coal tar, a black viscous liquid, when subjected to fractional distillation gives different products. These products on further distillation give various aromatic compounds like benzene. These compounds are the parent compounds used in the preparation of various industrially useful products such as dyes, drugs, polymers, pesticides, etc. TABLE 9.13\u2002 Fractional distillation of coal tar Main fraction Boiling point range (\u00b0C) Composition Light oil 80\u2013170 Benzene Middle oil 170\u2013230 Phenol, naphthalene Heavy oil 230\u2013270 Phenol, naphthalene, anthracene Green oil 270\u2013400 Anthracene Residue Pitch Above 400 Petroleum: It is a dark viscous oily liquid generally known as rock oil or crude oil. The word petroleum originated from Greek words petra\u2014meaning rock and oleum\u2014meaning oil. Composition of petroleum: The precise composition of petroleum cannot be specified since it depends on the place of origin. Nevertheless, petroleum can be considered a complex mixture of hydrocarbons, composed predominantly of alkanes and cycloalkanes. Some petroleum deposits also contain reasonable amounts of aromatic hydrocarbons and alkenes. Trace amounts of oxygen, nitrogen and sulphur are also present since it is obtained from the remains of dead plants and animals.","Organic Chemistry 9.21 Extraction of petroleum: Under earth\u2019s surface, petroleum deposits are found to be associated with a layer of natural gas. These can be drawn out by drilling deep wells through the various layers of earth till the oil-bearing strata are reached. Due to the process of drilling, pressure is developed in those layers. Consequently, the gases are fizzed out of the solution and the crude oil is gushed out. As the oil drawn out by this method is only 20 per cent, water or compressed air is pumped through the outer pipe and oil is drawn out through the inner pipe. By this way, it is possible to draw greater proportion of petroleum. Gases Gasoline Kerosene Diesel oil Lubricating oil Crude Steam oil FIGURE 9.4\u2002 Fractionating Tower Non-volatile fraction Processing of petroleum: Since the crude oil is drilled out from earth\u2019s crust, it obviously consists of lots of impurities. In addition to this, petroleum being a complex mixture of various hydrocarbons, it is necessary to separate the components. The process of removal of undesirable impurities followed by the separation into different useful fractions is called refining of petroleum. Refining of petroleum: The basic principle involved in refining petroleum is fractional distillation of the crude oil over a specific range of temperature as the different hydrocarbons have different boiling points. The refining is carried out in a fractionating tower. The fractionating tower is a tall cylindrical tower made up of a number of horizontal stainless steel troughs. The crude oil which is free from impurities is fed at the base of the fractionating tower at 675 K. At this temperature, all the volatile components vaporise and pass through the fractionating tower. As the vapour is passed through this column, they get condensed at different heights of the tower. The components which have higher boiling points get condensed first and the components having lower boiling points are carried to the top. Thus, the various fractions formed by condensation are collected in different trays separately. The non-volatile part of the crude oil remains in the tower in the form of a solid residue called asphalt. Before subjecting crude oil to fractional distillation, it should be freed from inorganic impurities. This is done by passing the raw crude oil between highly charged electrodes which remove all water from the sample. It is, then, treated with copper oxide to remove the sulphur compounds.","9.22 Chapter 9 TABLE 9.14\u2002 Useful fractions obtained after refining of petroleum Main fraction Boiling temperature Composition Uses Petroleum gas range Fuel, for making carbon black Crude naphtha C1\u2013C4 Solvent Below 30\u00b0C Motor fuel Kerosene Oil 30\u2013150\u00b0C \u2002(i)\u2002P\u0007etroleum ether Dry cleaning (below 90\u00b0C) (C5\u2013C7) 150\u2013300\u00b0C Cooking fuel illuminant (ii)\u2002\u0007Petrol oil gas (90\u2013120 \u00b0C) (C7\u2013C9) Motor fuel, cracking stock for petrol. (iii)\u2002\u0007Benzene (120\u00b0C\u2013150\u00b0C) (C9 \u2013 C10) Paint oil, lubricants Candles, matches, paints, C10\u2013C16 water proofing, ointments, protective paints. Fuel oil 300\u2013350\u00b0C C16\u2013C20 \u2002(i)\u2002Gas oil Lubricating oil 350\u2013400\u00b0C (ii)\u2002 Diesel oil (iii)\u2002 Furnace oil Paraffin wax Above 400\u00b0C C20\u2013C24 C24 and above Important Fuels Obtained from Petroleum The various components obtained by the process of fractional distillation of petroleum contains mixtures of hydrocarbons having different lengths of carbon chains. These fractions are used as fuels for different purposes after further purification. Purification makes the fuels devoid of corrosive constituents and unpleasant odours. \t1.\t\u0007Natural gas: Since all petroleum deposits are associated with natural gas, extraction of petroleum inevitably involves the collection of natural gas. Natural gas is composed of highly volatile alkanes, predominantly methane. Consequently, it undergoes rapid combustion releasing large amounts of heat. Natural gas has a wide range of applications in domestic and industrial activities. (a)\u2002\u0007Compressed natural gas can be used as an automobile fuel, i.e., as a substitute for petrol and diesel. It shows greater fuel efficiency and is available at a lower cost. (b)\u2002\u0007Natural gas can also be used as a domestic fuel. (c)\u2002\u0007Natural gas can be used as a raw material for the manufacture of carbon black and hydrogen. The hydrogen so obtained can be used in the synthesis of ammonia which is the most important component of nitrogenous fertilisers. CH4 + H2O \uf8e71\uf8e7100\uf8e7K \u2192 CO + 3H2 + 11.7 kJ high temperature N2 + 3H2 \uf8e7\uf8e7an\uf8e7Fde+pMr\uf8e7esosur\uf8e7e \u2192 2NH3 \t2.\t\u0007Petroleum gas: This is the most important by-product of petroleum processing. The major proportion of petroleum gas is n-butane, the minor components being ethane and propane. Petroleum gas, when subjected to high pressure, can easily pass into liquid state. This easy liquefaction of petroleum gas renders it a very useful domestic fuel in the form of LPG (liquefied petroleum gas).","Organic Chemistry 9.23 LPG: It has a high calorific value and burns in air with a blue non-luminous flame. It is associated with very low ignition temperature and can be lighted easily. This, being a colourless and odourless gas, is mixed with small amounts of ethyl mercaptan which imparts a characteristic unpleasant odour to LPG, thus, rendering easy detection of leakages. \t3.\t\u0007Petrol: The most important product of petroleum processing is petrol or gasoline which is used as a fuel for automobiles. In addition to this, it is also used for dry cleaning of clothes. Coal and petroleum have wide range of applications both in industry and day-to-day life. All the applications are based on the same principle of combustibility of hydrocarbons. Combustion being a highly exothermic process, the heat energy can be either directly used or can be trapped and converted to another form of energy and used. The domestic fuels like LPG, kerosene and biogas are important products of petroleum industry. Coal forms the most important fuel for the generation of electricity in thermal power plants. SOME IMPORTANT APPLICATIONS OF ORGANIC CHEMISTRY Chemistry has a very important role to play in our daily life and it is more so with organic chemistry. The food we consume, the cosmetics we use, the drugs we use for treating various diseases etc., are all made up of organic compounds. Therefore, it is not an exaggeration to claim that organic chemistry intrudes into each and every aspect of our day-to-day life. Use of Organic Compounds as Ingredients of Food It is a well-known fact that the food is made up of complex organic compounds such as carbohydrates, proteins, oils, fats, vitamins, etc. These are all quite essential for growth and maintenance of our body. In addition to these, there are other ingredients of food which are consumed in relatively lesser proportions. They include food preservatives and food colours. Food preservatives are chemical substances added to packed food items for the purpose of preventing spoilage of food material over a long period of usage. TABLE 9.15\u2002 Food preservatives and their fromulae Names Formulae Acetic acid (vinegar) CH3 COOH Sodium benzoate C6H5COONa Flavouring agents: These are chemical substances added in minor proportions which enhance the flavour and taste of the food materials. Examples: TABLE 9.16\u2002 Flavouring agents and their structures Names H2N \u2013 (CH2)2 C Structures Monosodium COONa glutamate (MSG) Esters of carboxylic acids COOH Citric acid or sodium RCOOR1 citrate (soft drinks) ds CH2 \u2013\u2013 COOH CH \u2013\u2013 COOH CH2 \u2013\u2013 COOH Certain chemical substances can be added to food items which impart colour to them.","9.24 Chapter 9 TABLE 9.17\u2002 Examples of food colours Names Colours Tartrazine Yellow Erithrocine Red Indigo Carmine (blue) Apart from all these, certain ingredients like caffein (alkaloid) are added to chocolates and soft drinks which act as stimulants to central nervous system. Other Ingredients Caffeine (alkaloid): It is generally added to soft drinks and chocolates. It acts as a stimulant to central nervous system. Citric acid or sodium citrate: Used as a flavouring agent in soft drinks. All these ingredients do not constitute essential part of our food. Since these substance have little or no nutritional value and their intake causes more harm to the body, the consumption of these substances should be either avoided or minimised. Just like in food materials, the role of chemicals in cleaning is also inevitable. Soaps and detergents are the most common commodities used for the purpose of cleaning. Use of Organic Compounds in Soaps and Detergents Soap is the sodium or potassium salt of higher fatty acids. Fatty acids are a class of organic compounds, which show characteristic acidic properties. Since fatty acids are the major constituents of vegetable oils, soaps are prepared by the hydrolysis of these oils in presence of an alkali like NaOH or KOH. The most commonly used oils are coconut oil, palm oil, cotton seed oil, ground nut oil, etc. Detergents are also used for the same purpose and possess similar structure except that detergents are sodium or potassium salts of benzene sulphonic acids. These acids are generally available or made from petroleum products. Structure and Composition of Soaps and Detergents Soap molecule is made up of a long chain of hydrocarbons attached to carboxylate group which constitutes anionic part of the molecule and positive part of Na+ and K+. C17H35COONa \u2192 C17H35COO\u2013Na+ Similarly a detergent molecule is composed of a long chain of hydrocarbons containing benzene ring attached to sulphonate group which constitutes the anionic part. C12H25 ONa C12H25 O\u2013 SO S O + Na+ O O Examples: Soap \u21d2 Sodium or potassium salt of stearic acid C17H35COONa","Organic Chemistry 9.25 Detergent \u21d2 Sodium laurate ONa C12H25 SO O Cleansing Action of Soaps and Detergents Generally, dirt is found to stick to the surface by means of an oily substance. Since oil and water are not miscible with each other, water cannot remove the dirt. When soap is dissolved in water, firstly it reduces the surface tension of water, thereby increasing the area of contact between water and dirt. Secondly, soap gets ionised into an anionic radical such as stearate radical and Na+ or K+ as cationic radical. The anionic radical consists of a hydrocarbon chain which is hydrophobic and a hydrophilic carboxylic acid as head. The hydrophilic end dissolves in water and the hydrophobic end mixes with the oil. Thus, soap forms a link between oil and water thereby separating the dirt which forms an emulsion with water and is removed off. Na+ + ++ + Na+ions O O Polar head + + \u2013\u2013\u2013 + C \u2013\u2013 + \u2013\u2013 + Non-polar \u2018tail\u2019 \u2013\u2013 + \u2013\u2013 \u2013\u2013 + \u2013\u2013\u2013 ++ (a) (b) FIGURE 9.5\u2002 (a) A soap molecule and (b) Cross-section of a soap micelle in water The detergents are also similar in structure and action to soaps. The basic difference between the soap and the detergent is that soap forms insoluble calcium and magnesium stearates on dissolution in hard water. On the other hand, detergents produce soluble calcium and magnesium sulphonates on dissolution in hard water. Therefore, detergents are more efficient with hard water when compared to soaps. However, detergents have a disadvantage of causing environmental pollution over soaps. Types of Soaps In addition to the sodium stearate which is the main ingredient, different types of soaps contain different additional ingredients which impart required quality to soaps. TABLE 9.18\u2002 Types of soaps and their chemical composition Type of soap Chemical composition Washing soap Toilet soap Washing soda in place of caustic soda Baby soap Caustic soda (for harder soaps) Transparent soap Caustic potash (for soft soaps) Mixture of oils and fats Olive oil as additional ingredient Glycerine and castor oil With the tremendous industrial and technological development of society, hydrocarbons and their derivatives continue to have more and more significant applications. Petroleum is the most important raw material for the manufacture of hydrocarbons. Therefore, it is a high time to realise","9.26 Chapter 9 that the rational and judicious use of exhaustible natural resources can go a long way in achieving sustainable development coupled with conservation of environment. EXAMPLE LPG contains butane and propane in major proportions whereas CNG contains methane as the major component. Justify. SOLUTION Both butane and propane can be liquefied relatively under moderate pressure and these liquefied forms readily vapourise under normal conditions. Moreover, the calorific value is high and almost equal in both cases. Easy liquefication of these gases permits easy transport and storage. Natural gas is associated with petroleum deposits. It contains methane as major component since it is the hydrocarbon having minimum boiling point and the most volatile. Petroleum being the mixture of hydrocarbons, methane volatilises and escapes out forming a layer of natural gas. EXAMPLE Some fractions of petroleum refining are used as dry cleaning liquids and some fractions are used as lubricating oils. What are the requisite characteristics of those fractions? SOLUTION The easily vapourisable fractions obtained from petroleum refining are used as dry cleaning liquids due to their volatile nature. The fractions which have higher boiling points are used as lubricating oils due to their high thermal resistance. EXAMPLE What is the composition of petroleum gas? Why is it used as a domestic fuel? SOLUTION Petroleum gas contains hydrocarbons with 1 \u2013 4 carbon atoms. It is used as a domestic fuel due to its high calorific value and also because of its easy liquefaction.","Organic Chemistry 9.27 TEST YOUR CONCEPTS Very Short Answer Type Questions \t1.\t Why was organic chemistry considered chemistry of \t16.\t What is meant by decarboxylation? How can meth- carbon compounds? ane be prepared by using this reaction? \t2.\t Name the first organic compound synthesised and \t17.\t Why is natural gas composed of major proportion of mention how it was synthesised. methane? \t3.\t State the modern definition of organic chemistry \t18.\t Cyclohexane is an example for ________ and justify. hydrocarbon. \t4.\t Unsaturated hydrocarbons give their characteristic \t19.\t On what basis is coal classified into different varieties? _______ reactions. \t20.\t How is ammonia manufactured from natural gas? \t5.\t Define catenation. What is its special significance \t21.\t Give the IUPAC names for the following with respect to organic chemistry? hydrocarbons. \t6.\t Give general formulae for alkanes, alkenes and \t\t(a)\t H3C CH2 CH CH3 alkynes. \t\t(b)\t H3C CH3 CH3 \t7.\t What are aliphatic hydrocarbons? How are they CH2 CH CH CH3 classified? \t22.\t Mention some uses of methane. \t8.\t The structure of isobutane is ______. \t23.\t Detergents are sodium salts of ________. \t9.\t What is primary suffix in the name of an organic compound? \t24.\t Write the position isomer for butyne. PRACTICE QUESTIONS 1\t 0.\t Why are coal and petroleum called fossil fuels? \t25.\t How is acetylene prepared from calcium carbide? Give equation. \t11.\t What are the techniques available for the extraction of coal from coal mines? \t26.\t What is the chemical reaction associated with the hydrogenation of oils? \t12.\t What is the principle involved in the refining of crude oil? \t27.\t What are soaps? How are detergents different from soaps in chemical composition? \t13.\t Calcium carbide, on hydrolysis, gives ______. \t28.\t __________ is the additive added to soap to make it \t14.\t What are natural gas and petroleum gas? transparent. \t15.\t What is meant by destructive distillation? What are \t29.\t ________end of soap dissolves in soft water. the products of destructive distillation of coal? \t30.\t What are food preservatives? Give two examples. Short Answer Type Questions \t31.\t What is meant by homologous series? What are its \t33.\t Define cracking. Explain the types of cracking. characteristics? \t34.\t Why are coal and petroleum considered non-\u00ad \t32.\t List out the characteristic properties of carbon renewable sources of energy? compounds. \t35.\t Explain the process of refining crude oil.","9.28 Chapter 9 \t40.\t Explain isomerism in alkanes. \t36.\t Explain the composition of petroleum. \t41.\t Explain the laboratory preparation of ethylene. \t37.\t By giving equations, explain the Decolourisation of \t42.\t How can CNG be a better alternative to petrol? bromine water by unsaturated hydrocarbons. \t43.\t Explain the advantages of detergents over soaps. \t38.\t Explain hydrogenation of ethene and ethyne. \t44.\t Explain the various ingredients added to food items \t39.\t Give the structural formulae of the first four mem- by giving examples. bers of homologous series of alkanes, alkenes and alkynes. Essay Type Questions \t45.\t Explain the unique features of carbon. \t48.\t Give the chemical properties of methane, ethane and ethyne. Give equations. \t46.\t Discuss in detail the important products of petro- leum processing. Give an account of their uses. \t49.\t Explain in detail the cleansing action of soaps and detergents. 4\t 7.\t Explain the extraction and processing of coal. For Answer key, Hints and Explanations, please visit: www.pearsoned.co.in\/IITFoundationSeries CONCEPT APPLICATION Level 1 Direction for questions from 1 to 7: \t10.\t 1-butene and 2-butene are ________isomers. State whether the following statements are true or false. \t11.\t Ethane can be prepared by decarboxylation of ______. \t1.\t Each homologous series is characterised by a gen- PRACTICE QUESTIONS eral formula. \t12.\t The method involved in refining of petroleum is \t ________. \t2.\t Pentane has three chain isomers. \t13.\t Hexane, on cracking, gives ______ and ______. \t3.\t All saturated hydrocarbons are aliphatic hydrocarbons. \t14.\t The best quality coal with respect to percentage of \t4.\t Methane can be prepared by the decarboxylation of carbon is _______. sodium methanoate. Direction for question 15: \t5.\t Hydrogenation reaction can be used to detect Match the entries in Column A with the unsaturation in an organic compound. appropriate ones in Column B. \t6.\t Ethyne on Polymerisation gives benzene. 15.\t Column A Column B \t7.\t Hexyne can decolourise bromine water. A. Natural gas (\u2002) a. Polymerisation of ethene Direction for questions from 8 to 14: B. Coke (\u2002) b. Benzene Fill in the blanks. C. Cn H2n (\u2002) c. Methane \t8.\t Closed chain hydrocarbons which do not resemble D. Kerosene aliphatic hydrocarbons in their chemical behaviour (\u2002) d. Destructive distillation of are called ________. coal \t9.\t IUPAC name of saturated straight chain hydrocar- E. C6H6 (\u2002) e. Refining of petroleum bon with 10 carbon atoms is ______. F. Polythene (\u2002) f. Alkene","Organic Chemistry 9.29 Direction for questions from 16 to 30: CH3 For each of the questions given below, four choices H3C \u2013 H2C \u2013 C C \u2013 CH \u2013 CH2 \u2013 CH3 have been provided. Select the correct alternative. \t16.\t Identify the compound which does not belong to \t\t(a)\u20022-ethyl-3-hexyne \t\t (b) 3-methyl-4-heptyne the same homologous series. \t\t(c)\u20025-methyl-3-heptyne \t\t(d)\u20025-ethyl-3-hexyne \t\t(a)\u2002propane\t (b)\u2002butyne \t\t(c)\u2002ethyne\t (d)\u2002hexyne \t17.\t The IUPAC name of \t23.\t The hydrocarbon obtained on heating calcium oxide with coke in an electric furnace which is followed CH3 CH CH CH CH3 by hydrolysis is || | C3H7 C2H5 C2H5 \t\t(a)\u2002C2H4\t (b)\u2002C2H6 \t \t(c)\u2002CH4\t (d)\u2002C2H2 \t\t (a)\u2002 3, 4-dlme thyl-4-ethyl Octane \t\t (b)\u2002 4-ethyl-3, 5-dimethyl Octane \t24.\t Which of the following can be the best substitute for \t\t (c)\u2002 2, 3-dimethyl-4-Propyl pentaee petrol as an automobile fuel? \t\t (d)\u2002 3, 4-dmieihyl-2-Propyl pentane \t\t(a)\u2002petrol\t (b)\u2002biogas \t18.\t The products of incomplete combustion of methane \t\t(c)\u2002kerosene\t (d)\u2002CNG are \t25.\t Structural formula of 3, 4-dimethyl heptane is \t\t (a)\u2002\u0007carbon and hydrogen. \t\t (b)\u2002 carbon monoxide and water. \t\t(a)\u2002CH3 \u2013 CH2 \u2013 CH2 \u2013 CH \u2013 CH \u2013 CH2 \t\t (c)\u2002 carbon dioxide and water. \t\t (d)\u2002 carbon monoxide end hydrogen. CH3 CH2 \u2013 CH2 \u2013 CH3 \t\t(b)\u2002CH3 \u2013 CH2 \u2013 CH2 \u2013 CH \u2013 CH3 \t19.\t Which among the following pairs belong to the CH3 CH2 \u2013 CH2 \u2013 CH3 same homologous series? CH3 \t\t(a)\u2002C3H4, C5H10\t (b)\u2002C2H6, C4H10 \t\t(c)\u2002CH3 \u2013 CH2 \u2013 CH \u2013 CH2 \u2013 CH2 \u2013 CH3 \t \t(c)\u2002C2H4, C4H8\t (d)\u2002C4H8, C5H10 \t\t(d)\u2002CH3 \u2013 CH2 \u2013 CH \u2013 CH2 \u2013 CH \u2013 CH2 \u2013 CH3 \t20.\t Which among the following isomers of hexane has CH3 CH3 PRACTICE QUESTIONS the highest boiling point? \t\t(a)\u2002CH3\u2013CH2\u2013CH2\u2013CH2\u2013CH2\u2013CH3 \t26.\t The primary suffix for a compound with general \t\t(b)\u2002CH3 CH | CH2 CH2 CH3 formula CnH2n-2 is CH3 \t\t(c)\u2002H3C \t\t(a)\u2002\u2013ane\t (b)\u2002\u2013yne \t\t(d)\u2002CH3 C| H3 \t\t(c)\u2002\u2013ene\t (d)\u2002\u2013enol CH2 C C| H3 \t27.\t A compound on hydrogenation yields ethane by CH3 consuming 2 molecules of hydrogen. The same compound on being treated with excess of bromine CH | CH | CH3 water gives CH3 CH3 \t\t(a)\u2002CH2Br2\t (b)\u2002C2H4Br2 \t21.\t The straight chain isomer of C4H10 is the major \t\t(c)\u2002C2H2Br4\t (d)\u2002C2H5Br component in __________. \t28.\t The reagent used for decarboxylation reaction is \t\t(a)\u2002biogas\t (b)\u2002petroleum gas \t\t (a)\u2002 NaOH + Ca(OH)2 \t\t (c)\u2002 natural gas\t (d)\u2002 coal gas \t\t (b)\u2002 only NaOH \t22.\t The IUPAC name of the following compound is \t\t (c)\u2002 NaOH + CaO _______. \t\t (d)\u2002 NaOH + CaCO3","9.30 Chapter 9 \t29.\t Which of the following structures does not corre- \t\t (c)\u2002\u00072 moles of carbon dioxide and 1 mole of water spond to the chain isomer of pentane? \t\t (d)\u2002\u00072 moles of carbon dioxide and 2 moles of water CH3 \t34.\t Which among the following molecular formulae represents a saturated hydrocarbon? \t\t(a)\u2002H3C CH2 C CH3 \t\t(a)\u2002C4H8\t (b)\u2002C4H6 H \t \t(c)\u2002C3H4\t (d)\u2002C5H12 CH3 \t35.\t Which among the following pairs belong to the same homologous series? \t\t(b)\u2002H3C C CH3 CH3 \t\t(a)\u2002C3H4, C5H10\t (b)\u2002C2H6, C4H8 \t \t(c)\u2002C2H4, C4H6\t (d)\u2002C4H8, C5H10 CH3 CH3 \t36.\t The number of bromine molecules required for the \t\t(c)\u2002H3C CH CH CH3 Decolourisation of 1 mole of ethene and ethyne are respectively CH3 \t\t (a)\u2002 one and three\t (b)\u2002 two and three \t\t(d)\u2002H3C CH CH2 CH3 \t\t (c)\u2002 one and two\t (d)\u2002 two and four \t30.\t Which of the following is not an alkene? \t37.\t Polymerisation of ethyne at 300\u00b0C gives \t\t(a)\u2002C4H8\t (b)\u2002C4H6 \t\t(a)\u2002polyethene\t (b)\u2002polyethyne \t \t(c)\u2002C3H6\t (d)\u2002C5H10 \t\t(c)\u2002benzene\t (d)\u2002polyvinyl chloride \t31.\t IUPAC name of a hydrocarbon is given as 3, \t38.\t The bromination of acetylene gives _________ as 5-Dimethyl-2-hexene. Identify the correct sequence the final product. of steps to draw its structural formula. \t\t(a)\u2002dibromoethane \t\t(1)\t numbering of carbon chain \t\t(b)\u2002tetrabromoethane \t\t(c)\u2002tetrabromoethene \t\t(2)\t locating the position of double bond \t\t(d)\u2002dibromoethene. \t\t(3)\t\u0007writing long chain corresponding to hexane \t39.\t Which of the following is an identification test for unsaturation in an organic compound? PRACTICE QUESTIONS \t\t(4)\tl\u0007ocating the methyl groups (prefixes) at the respective positions \t\t (a)\u2002 addition of hydrogen \t\t (b)\u2002 addition of ozone \t\t(5)\tp\u0007lacing hydrogens to satisfy tetravalency of \t\t (c)\u2002 addition of bromine \t\t (d)\u2002 addition of oxygen carbon \t\t(a)\u200213254\t (b)\u200232145 \t\t(c)\u200213245\t (d)\u200231245 \t40.\t The hydrocarbon used for welding purpose\u00a0is \t32.\t Identify the correct sequence of fractions obtained \t\t(a)\u2002ethane\t (b)\u2002ethyne when petroleum is subjected to fractional distillation. \t\t(c)\u2002ethene\t (d)\u2002benzene \t\t(1)\t lubricating oil\t\t (2)\u2002 petrol \t41.\t Coal gas mainly consists of \t\t (a)\u2002 methane, CO, H2 \t\t(3) petroleum ether\t\t (4)\u2002 diesel oil \t\t (b)\u2002 propane, CO2, H2 \t\t(a)\u20022341\t\t (b)\u20023241 \t\t (c)\u2002 methane, CO, H2O \t\t(c)\u20023214\t\t (d)\u20022431 \t\t (d)\u2002 methane, CO2, H2 \t33.\t 1 mole of ethyne on complete combustion gives \t42.\t The reagent NaOH + CaO is used for \t\t(a)\u2002carboxylation\t (b)\u2002dehydrogenation \t\t (a)\u2002\u00072 moles of carbon monoxide and half-mole of \t\t(c)\u2002hydrogenation\t (d)\u2002decarboxylation water \t\t (b)\u2002\u00074 moles of carbon dioxide and 1 mole of water","Organic Chemistry 9.31 \t43.\t Degradation of organic wastes in the absence of air \t\t (c)\u2002 iron oxide gives \t\t (d)\u2002 magnesium oxide \t\t(a)\u2002methane \t45.\t Petroleum fraction of which of the following com- \t\t (b)\u2002 methane, hydrogen, nitrogen and CO2 positions can be used as a lubricating oil? \t\t (c)\u2002\u0007methane, carbon monoxide and hydrogen \t\t (d)\u2002 methane, SO2 and hydrogen \t\t(a)\u2002C5\u2013C7 \t\t(b)\u2002C10\u2013C16 \t44.\t Sulphur compounds in crude oil can be removed by \t\t(c)\u2002C20\u2013C24 using \t\t(d)\u2002C30\u2013C40 \t\t (a)\u2002 copper oxide \t\t(b)\u2002alumina Level 2 \t1.\t Write all possible chain isomers for pentene and \t8.\t Give the structural formulae of four compounds of hexyne. the homologous series succeeding the one having molecular formula C3H4. Also give their molecular \t2.\t Give IUPAC names for the following: weights. \t\t(a)\u2002H3C CH CH2 CH = CH2 \t9.\t Compound X can be prepared by passing a gas Y through a metal tube which is at very high tempera- CH3 CH3 ture. Y on treatment with 2 g of hydrogen gas in CH2 CH3 presence of nickel gives a compound Z. Z can also \t\t(b)\u2002HC be prepared by treating ethyl alcohol with \u2018ic\u2019 acid of sulphur at 170\u00b0C. Y can also be prepared by hydro- CH3 C2H5 lysis of \u2018A\u2019. Identify X, Y, Z and A and write all the C CH3 balanced chemical equations. \t\t(c)\u2002HC \u2261 C \t10.\t Two containers A and B are filled with the same H amount of chlorine gas. Limited amount of methane CH3 is passed into container \u2018A\u2019 and excess of methane into container \u2018B\u2019. Identify the products formed in \t\t(d)\u2002H3C CH = CH CH CH3 A and B. Give a reason in support of your answer. PRACTICE QUESTIONS \t3.\t A hydrocarbon \u2018X\u2019 can have only three chain isomers \t11.\t The vapour density of an unsaturated aliphatic and one of the isomers consists of same alkyl groups hydrocarbon \u2018X\u2019 is 34. Write the structural formula attached to central carbon atom with single bonds. of X and its succeeding homologue Y. Also write Identify the preceding and succeeding homologue the position isomers of X and Y. of \u2018X\u2019. \t12.\t How does the burning of coal lead to air pollution as \t4.\t Explain the role of natural gas in the preparation of well as water pollution? ammonium fertilisers. \t13.\t At the end of the process of preparation of soap, \t5.\t A straight chain saturated hydrocarbon with vapour common salt is added. Explain the role of common density 43 on heating in absence of air gives X and salt in that process. Y.Y on treatment with bromine water gives Z. Identify X, Y and Z. \t14.\t A compound X on hydrolysis produces a gas Y which on hydrogenation produces a gas Z which can deco- \t6.\t The percentage composition of a hydrocarbon \u2018X\u2019 lourise bromine water forming a compound with is 90 per cent carbon and 10 per cent hydrogen, molecular weight 188 a.m.u. Identify X, Y and Z. respectively. Write the structural formulae of two successive and preceding homologues of\u00a0X. \t15.\t Two students Rishi and Kushi were preparing for International Chemistry Olympiad. They had come \t7.\t Why are some coal deposits associated with large amounts of sulphur?","9.32 Chapter 9 across a question. In that, a table of boiling points of \t21.\t Write IUPAC names for the following structures: members of homologous series of alkanes was given and similar trend is followed in other classes of com- CH3 pounds also. Predict the trend observed. What reason can be attributed to the above trend? \u2014 \u2014\u2014 \t16.\t In an organic chemistry laboratory, a scientist sub- \t\t(a)\u2002H3C \u2013 CH \u2013 C \u2013 CH3 jected a hydrocarbon to combustion. The products occupied a volume ratio of 4 :\u00a0 3 under the same OH CH3 conditions of temperature and pressure. The scien- Cl tist drew the possible structures of the hydrocarbon. She then subjected the compound to ozonolysis to \u2014 identify the exact structure. Predict the products \u2014 formed when the compound is treated with bro- \t\t(b)\u2002H3C \u2013 CH \u2013 CH2 \u2013 CH \u2013 CH3 mine water. COOH 1\t 7.\t A research scholar, during his experiment came across an aliphatic hydrocarbon \u2018X\u2019. In the process \t\t(c)\u2002CH3 \u2013 CH \u2013 C = CH \u2013 CH3 of identification of \u2018X\u2019 he passed \u2018X\u2019 through alka- \u2014 line KMnO4. The solution became colourless. He \u2014 found out the vapour density of the compound to be 34. Identify X and its succeeding homologue CH3 CH3 \u2018Y\u2019 and also position isomers of straight chain isomers. \t\t(d)\u2002H3C \u2013 CH \u2013 CH2 \u2013 CH = CH2 \u2014\u2014 \u2014 \t18.\t The molar ratio of carbon dioxide and water pro- \u2014CH3 C2H5 duced by the combustion of one mole of an ali- CH3 phatic hydrocarbon \u2018X\u2019 is 5 : 4. Write the possible structures of X. What happens when \u2018X\u2019 is passed \t\t(e)\u2002H3C \u2013 C \u2013 CH3\t(f)\u2002HC \u2261 C \u2013 CH3\u2014\u2014 through bromine water? CH3 H \t19.\t The government had a proposal for establishing a thermal power plant where coal would be the CH3 source of power. A panel has been sent to the site to examine the feasibility of the proposal. The farm- \t\t(g)\u2002H3C \u2013 CH \u2013 CH \u2013 CH \u2013 CH3 ers in that area became panicky that their soils may become less fertile and may even become unfit for \t22.\t \u2018X\u2019 is an alicylic hydrocarbon with the molecu- cultivation. However, the panel members convinced them by giving an assurance that the best quality coal lar formula C4H8. Y is the corresponding aliphatic will be used in the plant to minizise the effect. Can compound. Give all the possible isomers of Y and you explain the reason why burning of coal makes the soil loses fertility and how quality of coal has a their IUPAC names. Identify the products of bro- bearing on the above? What other effects does burn- ing of coal have on the environment? mination. When Y is treated with hydrogen what are the products formed? How are these products \t20.\t CNG is a better automobile fuel when compared to petrol and diesel. Give reasons. separated from the mixture? PRACTICE QUESTIONS Level 3 \t23.\t Coke is obtained by the destructive distillation of coal. But, coke is considered to be the purer form of carbon than coal. Give a reason. \t24.\t Give reasons for the following: \t\t (a)\u2002\u0007Petroleum deposits are always associated with a layer of natural gas \t\t (b)\u2002\u0007The volatile products obtained by distillation of coal are passed through water. \t\t (c)\u2002\u0007A mixture of acetylene and oxygen is used for welding metals. \t\t (d)\u2002\u0007Anthracite coal is of better quality than bitumi- nous coal. \t\t (e)\u2002\u0007It is possible to prepare an alkane with one car- bon atom from a carboxylic acid with two car- bon atoms. \t1.\t Chloromethane has a certain value of dipole moment \t2.\t \u2018Carbon is not the only element showing catenation. even though the dipole moment value of methane is However, carbon is the only element forming mil- zero. Justify. lions of compounds.\u2019 Comment on the statement.","Organic Chemistry 9.33 \t3.\tCoal has a major role to play in the production of \t7.\tCan kerosene be used as a substitute for petrol in steel. Explain the role of coal. automobiles? Give reasons in support of your answer. \t4.\tPetrol used in automobiles obtained by fractional \t8.\tIodination of methane is carried out in the presence distillation is less preferred over the petrol obtained of oxidizing agents like iodic acid or HNO3. How by cracking. Justify. do you account for this? \t5.\tWhy do detergents cause pollution? How do newly \t9.\tWhy are shaving creams and shampoos softer than developed biodegradable detergents differ from soap? them? \t10.\t \u2018The same coal deposit is found to contain variable \t6.\tFluorination of methane is explosive. How do you composition of coal.\u2019 Justify. account for this? How can fluorination of methane be carried out? PRACTICE QUESTIONS","9.34 Chapter 9 CONCEPT APPLICATION Level 1 True or false 2.\u2002True\t 3.\u2002True\t 4.\u2002False 6.\u2002 Tru\t 7.\u2002True \t1.\t True\t \t5.\t True\t Fill in the blanks \t9.\t decane \t10.\t position \t12.\t fractional distillation \t13.\t ethene, butane \t8.\t aromatic hydrocarbons \t11.\t sodium propanoate \t14.\t anthracite Match the following B : d\t C:f E : b\t F:a \t15.\t A : c\t \t\tD : e\t Multiple choice questions \t16.\t a \t20.\t a \t24.\t d \t28.\t c HINTS AND EXPLANATION \t17.\t b \u2014\u2014\t21.\t b\t25.\t b\t29.\t c \u2014\u2014 \t18.\t b \t22.\t c \t26.\t b \t30.\t b \t19.\t d \t23.\t d \t27.\t c \t31.\t (i)\t\u0007locating the long chains corresponding to \t34.\t Saturated hydrocarbons have the general formula hexane CnH2n+2 and C5H12 corresponds to that formula. \t\t(ii)\t\u0007numbering of carbon chain \t35.\t C4H8 and C5H10 belong to same homologous series of alkenes as they possess same general formula \t\t(iii)\t\u0007locating the position of double bond (CnH2n) \t\t(iv)\t\u0007locating the methyl groups (prefixes) at the \t36.\t H2C = CH2 + Br2 \u2192 BrH2C \u2013 CH2Br respective position Br Br \t\t(v)\t\u0007locating hydrogen molecules to satisfy tetrava- lency of carbon \t32.\t (i)\t\u0007petroleum ether HC \u2261 CH + 2Br2 \u2192 H \u2013 C \u2013 C \u2013 H \t\t(ii)\t\u0007petrol \t\t(iii)\t\u0007diesel oil Br Br \t\t(iv)\t\u0007lubricating oil \t\tOne mole of ethene requires one mole of bromine \t33.\t C2H2 + 5O2 \u2192 2CO2 + H2O and one mole of ethyne requires two moles of bro- mine for Decolourisation \t\tWhen one mole of ethyne is subjected to complete combustion, 2 moles of CO2 and 1 mole of water \t37.\t Polymerisation of ethyne at 300\u00b0C gives benzene are formed \t38.\t The bromination of acetylene gives tera bromo ethane.","39.\t Addition of bromine is used as an identification Organic Chemistry 9.35 test for detection of unsaturation in an organic compound as bromine is a reddish brown liquid and \t42.\t The reagent NaOH + CaO is called soda lime and loses colour due to the addition reaction. is used for decarboxylation. \t40.\t The hydrocarbon used for welding purposes is acet- \t43.\t When organic wastes undergo degradation in the ylene (ethyne) since oxyacetylene flame produces a absence of air, methane is formed. high temperature of 3800\u00b0C. \t44.\t Sulphur compounds in crude oil can be removed by \t41.\t The constituents of coal gas are methane, carbon using copper oxide. monoxide and hydrogen. \t45.\t The composition of lubricating oil is hydrocarbons in the range C20\u2013C24 due to high boiling point. Level 2 \t7.\t (i)\t\u0007composition of submerged plants HINTS AND EXPLANATION \t1.\t structures of the compounds. \t\t(ii)\t\u0007process of decay of submerged plants \t2.\t rules for IUPAC nomenclature. \t\t(iii)\t\u0007changes that take place in submerged plants \t3.\t (i)\t\u0007identification of hydrocarbon \u2018X\u2019 \t8.\t characteristics of homologous series \t\t(ii)\t\u0007valency of carbon atom. \t\t(iii)\t\u0007relation between valency of carbon atom and \t9.\t (i)\t\u0007identification of Z the number of single bonds it can form. \t\t(ii)\t\u0007identification of Y from Z \t\t(iv)\t\u0007identification of hydrocarbon on the basis of \t\t(iii)\t\u0007identification of X from given reaction of\u00a0Y number of chain isomer. \t\t(v)\t\u0007Prediction of molecular formula from the \t\t(iv)\t\u0007identification of A from Y structure of hydrocarbon. \t10.\t (i)\teffect of amount of methane on product \t\t(vi)\t\u0007Identification of preceding and succeeding formation homologues of hydrocarbon. \t\t(ii)\t the initial product formed in container A \t\t(iii)\t comparison of amounts of methane and prod\u00ad \t4.\t (i)\t\u0007raw materials for preparation ammonia. \t\t(ii)\t\u0007reaction of chief constituent of natural gas to uct present is container A with time \t\t(iv)\tcomparison of reactivity of methane and give the raw material required. \t\t(iii)\t\u0007Haber\u2019s process product with chlorine \t\t(iv)\t\u0007role of product of Haber\u2019s process in manufac- \t\t(v)\t final products formed in container A \t\t(vi)\t product formed in container B based on avail- turing ammonium fertilisers ability of reactants \t5.\t (i)\t\u0007calculation of molecular weight of hydro- carbon \t11.\t (i)\t calculation of molecular weight of X \t\t(ii)\t calculation of molecular formula of hydrocar\u00ad \t\t(ii)\t\u0007identification of molecular formula of hydro- carbon based on given data bon from molecular weight \t\t(iii)\t identification of type of hydrocarbon based on \t\t(iii)\t\u0007identification of products namely X and Y of hydrocarbon upon cracking formula \t\t(iv)\t identification of possible ways the atoms can \t\t(iv)\t\u0007identification of Z from bromination of\u00a0X be arranged \t6.\t (i)\t\u0007identification of atomic ratio \t\t(v)\t identification of succeeding homologue of the \t\t(ii)\t\u0007calculation of simple atomic ratio from atomic above hydrocarbon ratio \t\t(vi)\t number of position isomers of succeeding \t\t(iii)\t\u0007calculation of integral ratio and molecular for- homologue based on number of carbon atoms mula from simple atomic ratio \t\t(iv)\tp\u0007rediction of succeeding and preceding \t12.\t (i)\t impurities in coal homologues of above hydrocarbon \t\t(ii)\t different reactions of coal on burning \t\t(iii)\t effect of products of burning of coal on envi\u00ad ronmental pollution","9.36 Chapter 9 \t13.\t (i)\t application of Le Chatelier principle \t\tSince it reacts with bromine water and its formula \t\t(ii)\t composition of soap indicates that X is butyne \t\t(iii)\t types of reactions involved in the preparation \t\t\u2234 X may be 1-Butyne or 2-Butyne of soap Br Br \t\t(iv)\t effect of common salt on the final step of the reaction CH3 \u2013 CH2 \u2013 C \u2261 CH Br2 \/H2O CH3 \u2013 CH2 \u2013 C \u2013 CH\u2014\u2014 \u2014\u2014 1\u2013Butyne Br Br \t14.\t (i)\t identification of Z (Y) 1, 1, 2, 2-tetrabromo ethane \t\t(ii)\t nature of \u2018Z\u2019 Br Br Br Br \t\t(iii)\t identification of \u2018Y,\u2019 based on its hydrogena- CH3 \u2013 C \u2261 C \u2013 CH3 Br2 \/H2O CH3 \u2013 C \u2013 C \u2013 CH3 H3C \u2013 C \u2013 C \u2013 CH3 tion reaction Br Br \t15.\t The van der Waal\u2019s forces which hold the non-alkane (Y) molecules are weak and have a very short range. The \u2014\u2014 larger the molecule, the stronger are the intermo- \u2014\u2014 lecular forces. Since boiling point depends upon the \u2014\u2014 intermolecular forces, the boiling points of alkanes \u2014\u2014 increase with increase in chain length. Also as the molecular weight increases, the velocity of the mol- 2\u2013 Butyne Br Br ecule decreases at a particular temperature. Thus, 2, 2, 3, 3-tetrabromo ethane alkanes tend to be in a liquid or a solid state. \t17.\t Molecular mass of X is 68. It may be alkene or \t16.\t General combustion equation is alkyne. \t\tAlkene\tAlkyne \u2234 Cn H2n CnH2n \u2212 2 12n + 2n = 68 12n + 2n \u2212 2 = 68 \u21d2n=5 14n = 68 \u2234 X is C5H8 n = 68 \t \t\t 14 CxHy \uf8eb x y \uf8f6 O2 \u00d7.CO2 y H2C \t\tBut it is impossible. \uf8ed 4 \uf8f8 2 + + \u2192 + \t\tSucceeding homogolue \u2018Y\u2019 is C6H8 (hexyne) Position isomers of X are 1-Pentyne, 2-Pentyne. Position iso- \t\tAs the molar ratio of CO2 and H2O is 4 : 3, y mers of Y are 1-Hexyne, 2-Hexyne and 3-Hexyne. 2 HINTS AND EXPLANATION x=4 and = 3 \u21d2 y = 6 1\t 8.\t The molecular formula of hydrocarbon giving CO2 and H2O in 5 : 4 ratio can be C5H8. \u2234 X = C4H6 \t\t(I)\u2002 HC \u2261 C \u2014 CH2 \u2014 CH2 \u2014 CH3 + Br2 \u2192 HC = C \u2014 CH2 \u2014 CH2 \u2014 CH3 + Br2 \u2192 Br Br \u2014 \u2014\u2014 \u2014 \u2014\u2014 \u2014\u2014 Br Br HC \u2014 C \u2014 CH2 \u2014 CH2 \u2014 CH 1, 2-dibromo -1-pentene Br Br \t\t(II)\u2002H3C \u2014 C \u2261 C \u2014 CH2 \u2014 CH3 + Br2 \u2192 H3C \u2014 C = C \u2014 CH2 \u2014 CH3 1, 1, 2, 2-tetrabromopentane Br Br 2, 3-dibromo 2-pentene + Br2 Br Br \u2014\u2014 \u2014\u2014 H3C \u2014 C \u2014 C \u2014 CH2 \u2014 CH2 \u2014 CH3 Br Br 2, 2, 3, 3-tetrabromopentane Br Br Br Br \u2014 \u2014\u2014 \u2014\u2014 \u2014 \u2014 \u2014 \t\t(III)\u2002HC \u2261 C \u2014 CH \u2014 CH3 + Br2 \u2192 HC = C \u2014 CH \u2014 CH3 + Br2 \u2192 HC \u2014 C \u2014 CH \u2014 CH3 \u2014 CH3 CH3 Br Br CH3 1, 2-dibromo - 3-methyl 1-butene 1, 1, 2, 2-tetrabromobutane","Organic Chemistry 9.37 \t19.\t C\u0007 oal is formed from various organic compounds. \t\t(a) In coal along with carbon, nitrogen and sulphur are also present in varying amounts. When the coal is CH3 \u2013 CH CH \u2013 CH3 Br2\/H2O H3C \u2013 CH \u2013 CH \u2013 CH3 burnt the N and S form corresponding oxides which escape into the atmosphere. These oxides com- 2\u2013butene \u2014Br Br bine with water forming their corresponding acids \u2014 namely HNO3 and H2SO4. These acids reach earth H2\/ Pt 2, 3-dibromo butane\u2014\u2014 as acid rain. As a result, the acidity of soil increases. Anthracite coal is the best type of coal as it contains CH3 \u2013 CH2 \u2013 CH2 \u2013 CH3 least percentage of `S\u2019 and `N\u2019 and minimises the butane effect of acidity of soil to the maximum extent. \t\t(b) \t20.\t In CNG, the major component is methane. Since the calorific value is more and the products formed Br2\/H2O CH3 \u2013 CH2 \u2013 CH \u2013 CH2 as a result of combustion are less polluting agents when compared with petrol and diesel, it is pre- CH3 \u2013 CH2 \u2013 CH = CH2 H2\/Pt Br Br ferred. Petrol and diesel are mixtures of hydrocar- 1 \u2013 butene 1, 2 \u2013 dibromo butane bons where incomplete combustion takes place forming carbon monoxide which cases air pollu- CH3 \u2013 CH2 \u2013 CH2 \u2013 CH2 tion. Moreover in petrol and diesel sulphur and butane nitrogen are present which form corresponding oxides. These oxides cause air pollution. Further \t\t(c) Br2\/H2O CH3\u2014\u2014 CNG undergo rapid combustion due to its low H2\/Pt \u2014 ignition temperature. CH3 \u2013 C = CH2 CH3 \u2013 C \u2013 CH2 CH3\u2014 \t21.\t (a)\t 3, 3-Dimethyl-2-butanol Br Br 2 \u2013 methyl propane 1, 2 \u2013 dibromo \u2013 2 \u2013 methyl propane\u2014 \t\t(b)\t 4-Chloro-2\u2013methyl pentanoic acid CH3 \u2013 CH \u2013 CH2 \t\t(c)\t 3, 4-Dimethyl-2-pentene CH3 2 \u2013 methyl propane \t\t(d)\t4-Methyl-1-pentene \t\tTherefore, the hydrogenated products are n-butane HINTS AND EXPLANATION \t\t(e)\t 2, 2-Dimethyl propane C in case (a), (b) and isobutene in case if\u00a0 (c). Among these two n-butane is having high boiling \t\t(f)\t3-Methyl-1-pentyne point than isobutane. The boiling point is propor- tional to surface area of the molecule, more is the \t\t(g)\t4-Methyl-2-pentene surface area more are the intermolecular forces of attraction between the molecules. So, its boiling \t22.\t X is cyclobutane point increases. Between n-butane and isobutene n-butane is having high surface area; so, boiling \t\tY is butane point is more when compared to isobutene. Hence, these two can be separated by fractional distillation. \t\tIsomers of Y are \t23.\t Coal contains appreciable proportion of sulphur \t\t(a)\u2002 CH3 \uf8e7 CH = CH \uf8e7 CH3, and nitrogen as it is formed by the degradation of 2 \u2212 Butene dead organic matter. During destructive distillation of coal, sulphur and nitrogen are removed and coke \t\t(b)\u2002 CH3 \uf8e7 CH2 = CH = CH2 is obtained which is a purer form of carbon. 1 \u2212 Butene \u2014 \t24.\t (a)\t The most volatile hydrocarbons under the \t\t(c)\u2002 3CH3 \u2014 2C = 1CH2 earth\u2019s crust vaporise under high temperature and pressure conditions and form a layer of CH3 natural gas. 2 \u2013 Methyl \u2013 1 \u2013 Propene \t\t(b)\t The volatile products obtained by distillation \t\t (a), (b) are position isomers. (a) and (c) as well as (b) of coal may contain some water soluble gases and (c) are chain isomers. such as NH3 as impurities. Therefore, they are passed through water to remove the volatile impurities. \t\t(c)\t Acetylene undergoes combustion to produce large amount of heat. A mixture of acetylene","HINTS AND EXPLANATION 9.38 Chapter 9 sulphur and nitrogen contribute much to the air and water pollution, anthracite coal is con- and oxygen produces a temperature of 3800\u00b0C sidered as a better type of coal. which is higher than the melting points of met- als. Therefore, it is used for welding purpose. \t\t(e)\t Decarboxylation involves removal of CO2 \t\t(d)\t Anthracite coal contains 90 per cent carbon and resultant reduction in number of carbon and 10per cent of other components such as atoms from the parent carboxylic acid. Hence, sulphur or nitrogen. Bituminous coal contains alkane with one carbon atom is prepared from 70 per cent carbon and 30 per cent of other carboxy\u00ad lic acid with two carbon atoms. components such as sulphur and nitrogen. As with inert gas like He or Ne or N2, the rate of Level 3 the reaction can be decreased. And also when the reaction is carried in a copper vessel copper being \t1.\t (i)\t\u0007the nature of bonds in CH3CI and CH4 good conductor of heat, absorbs excess heat and \t\t(ii)\t\u0007nature of the constituent atoms present in the thus makes the reaction to be moderate. respective molecules \t7.\t No, kerosene cannot be used as a substitute for p\u00ad etrol \t\t(iii)\t\u0007reason for dipole moment of a molecule as an automobile fuel. Pasoline has lower \u00adignition temperature and the hydrocarbons have carbon \t3.\t (i)\t composition of steel chain length ranging from C5\u2013C10. Kerosene has \t\t(ii)\t\u0007compound formed with major constituent of higher ignition temperature and the hydrocarbons have carbon chain length ranging from C10 to C18. coal and that of major constituent of steel Due to higher ignition temperature, kerosene can- \t\t(iii)\t\u0007effect of formation of this compound on steel not be ignited by spark plug. Because of longer car- bon chain, it produces very high knocking which \t4.\t (i)\t\u0007comparison of the components present in pet- makes it unsuitable for use as an automobile fuel. rol obtained by fractional distillation and by cracking \t8.\t Chlorination of methane gives methyl chloride and hydrochloric acid, which are stable, where as iodin- \t\t(ii)\t\u0007comparison of products obtained on fractional ation of methane gives methyl iodide and hydrogen distillation and cracking of petrol iodide which is a strong reducing agent and hence reduces CH3\u2013I to CH4. \t\t(iii)\t\u0007effect of the products on the characteristic reaction involved in the usage of petrol as fuel \t\tSo, iodination is reversible: \t\t(iv)\t\u0007comparison of type and nature of products CH4 + I2 CH3I + HI produced by the two types of petrol \t\tAs a result iodination is carried out in the presence \t\t(v)\t\u0007comparison of effect of these products on the of oxidizing agent like HIO3 which oxidises HI to environment I2 and thus prevents the reversibility of the reaction. \t\t(vi)\t\u0007comparison of effect of products obtained on 5HI + HIO3 \u2192 I2 + H2O knocking property of engines CH4 + I2 \uf8e7\uf8e7HIO\uf8e73 \u2192 CH3I + I2 + H2O \t5.\t (i)\t\u0007structure of non-polar hydrocarbon part of detergent molecule \t9.\t Soaps are prepared by subjecting oils or fats to hydro- lysis with sodium hydroxide. That means, soaps are \t\t(ii)\t\u0007effect of structure on degradation sodium salts of higher fatty acids. Shampoos and \t\t(iii)\t\u0007structure of biodegradable detergents shaving creams are prepared by subjecting oils or \t\t(iv)\t\u0007comparison of structures of biodegradable and fats to hydrolysis with potassium hydroxide. That means they are potassium salts of higher fatty acids. non-bio-degradable detergents \t6.\t Attack of fluorine on methane is highly exothermic reaction with very less activation energy. The high amounts of energy released in this step make the fluorine molecules to dissociate in greater number leading to a greater increase in the rate of reaction, which ultimately makes the reaction explosive. Hence the mixture of CH4 and F2 when diluted","Potassium salts are more soluble than sodium salts. Organic Chemistry 9.39 Hence shampoos and shaving creams are softer than soaps. content by the removal of hydrogen and oxygen in the form of water. As they become richer in car- \t10.\t Coal is formed when wood and plant remains bon, the quality of coal goes on increasing from the decompose in the absence of air. They contain car- stage of peat to the stage of anthracite. This is the bon, hydrogen and oxygen. The process of gradual reason why the same coal deposit may contain coal decomposition results in the increase of carbon of different compositions. HINTS AND EXPLANATION","This page is intentionally left blank.","Notes","Notes"]