Advanced Theory in Organic Chemistry By MS Chouhan

Glossary 587 equilibrium (right-hand product favoured) transformation in either direction (but not equilibrium) resonance curly arrow-movement of two electrons curly arrow-movement of one electron Information on arrows A ¾¾a® B reaction with a converts A into B A ¾a¾¾/b® B reaction with a in the represence of b converts A into B A ¾a¾/so¾lve¾nt ® B reaction with a in suitable solvent converts A into B A ¾¾a® B reaction with a at tºC, for h hours converts A into B t°,h,hr A ¾¾a® ¾¾b® B reaction with a first, then with b converts A into B or reagent a achieves conversion A ® B, A ¾(¾i)¾a® B reagent b achieves conversion B ® A, (ii) b AB TABLE 2.4 SOLUBILITIES OF ALCOHOLS IN WATER Formula Name Solubility in water (g/100 g) Methanol Infinitely soluble CH3OH Ethanol Infinitely soluble CH3CH2OH Propanol Infinitely soluble CH3(CH2)2OH Butanol 9 CH3(CH2)3OH Pentanol 2.7 CH3(CH2)4OH Hexanol 0.6 CH3(CH2)5OH Heptanol 0.18 CH3(CH2)6OH Octanol 0.054 CH3(CH2)7OH Decanol Infinitely soluble CH3(CH2)9OH

588 Advance Theory in ORGANIC CHEMISTRY Bond D (kJ/mol) Bond D (kJ/mol) Bond D (kJ/mol) H—H 436 369 H—F 570 (CH3)3C — I 227 (CH3)2CH — CH3 363 H — Cl 431 H2C == CH — H 464 (CH3)3C — CH3 426 H — Br 366 H2C == CH — Cl 396 H2C == CH — CH3 318 H—I 298 H2C == CHCH2 — H 369 H2C == CHCH2 — CH3 728 Cl — Cl 242 H2C == CHCH2 — Cl 298 427 472 H2C == CH2 H CH3 Br — Br 194 Cl 400 CH2—CH2 325 I— I 152 CH2—H 375 O 374 CH3 — H 439 || 497 CH3 — Cl 350 CH2—Cl 300 CH3 C— H 211 CH3 — Br 294 HO — H 440 Br 336 HO — OH OH 464 CH3O — H CH3 — I 239 HC == C — H 558 CH3S — H 336 CH3 — OH 385 377 441 CH3 — NH2 386 CH3 — CH3 370 C2H5O — H 352 C2H5 — H 421 C2H5 — CH3 C2H5O — H 355 O || CH3 C— CH3 C2H5 — Cl 352 NH2 — H 450 C2H5 — Br 293 H — CN 528 C2H5 — I 233 C2H5 — OH 391 (CH3)2CH — H 410 (CH3)2CH — Cl 354 (CH3)2CH — Br 299 (CH3)3C — H 400 (CH3)3C — Cl 352 (CH3)3C — Br 293 In other words, exothermic reactions are favored by products with strong bonds and by reactants with weak, easily broken bonds.

Table Dipole Moments of Some Compounds Glossary 589 Compound Dipole moment(D) Compound Dipole moment(D) NaCl 1.47 CH2O 9.00 NH3 1.31 CH3Cl 2.33 CH3NH3 0 H2O 1.87 0 1.85 CO2 0 CH3OH 1.70 CH4 0 CH3CO2H 1.70 CH3CH3 CH3SH 1.52 Benzne COMPOUNDS NAMED AS ACRONYMS Some compounds are referred to by acronyms, shortened versions of either their systematic or their trivial name. We just saw TNT as an abbreviation for TriNitroToluene but the commoner use for acronyms is to define solvents and reagents in use all the time. Later in the book you will meet these solvents. Me O O Me N H Me S Me THF O DMSO (TetraHydroFuran) (DiMethylSulfOxide) DMF (DiMethylFormamide) The following reagents are usually referred to by acronym and their functions will be introduced in other chapters so you do not need to learn them now. You may notice that some acronyms refer to trivial and some to systematic names. There is a glossary of acronyms for solvents, reagents, and other compounds on p. 000. Me Me Me H Me Al O O Me N Me Me Me + N Cl Cr O– EtO2C N N CO2Ct Li H LDA DIBAL PCC DEAD LithiumDi-isopropy Amide Di-IsoButylALuminiumhydride Pyridinium ChloroChromate DiEthyl Azo-Dicarboxylate

590 Advance Theory in ORGANIC CHEMISTRY Summary Asymmetric carbon The carbon atom which is attached with four different groups of atoms is called asymmetric carbon. Asymmetric molecule If all the four aubstituents attached to carbon are different, the resulting molecule will lack symmetry. Such a molecule is called asymmetric molecule. Asymmetry of molecule is responsible for opitcal activity in such organic compounds. Achiral molecule A molecule that is superposable on its mirror image. Achiral molecules lack handedness and are incapable of existing as a pair of enantiomers. Axial bond The six bonds of a cyclohexane ring (below) that are perpendicular to the general plane of the ring, and that alternate up and down around the ring. Boat conformation A conformation of cyclohexane that resembles a boat and that has eclipsed bonds along its two sides. Chair conformation The all-staggered conformation of cyclohexane that has no angle strain or torsional strain and is, therefore, the lowest energy conformation. Chiral molecule A molecule that is not superposable on its mirror image. Chiral molecules have handedness and are capableof existing as a pair of enantiomers. Chirality The property of having handeness. Configuration The particular arrangement of atoms (or groups) in space that is characteristic of a given stereoisomer. Conformation A particular temporary orientation of a molecule that results from rotations about its single bonds. Conformational anylysis An analysis of the energy changes that a molecule undergoes as its groups undergo rotation (sometimes only partial) about the single bonds that join them. Conformer A particular staggered conformation of a molecule. Connectivity The sequence, or order, in which the atoms of a molecule are attached to each other. Dextrorotatory Those substances which rotate the plane of polarisation of light towards right are called dextrorotatory. Currently, dextro and laevo rotations are represented by algebraic signs of (+) and (–) respectively. Leavorotatory A compound that rotates plane polarized light in a counterclockwise direction.

Glossary 591 Eclipsed conformation A temporary orientation of groups around two atoms joined by a single bond such that the groups directly oppose each other. Enantiomers Stereoisomers that are mirror images of each other. enantiomers rotate the plane of polarised light to the same extent but in opposite direction. Equatorial bond The six bonds of a cyclohexane ring that lie generally around the “equator” of the molecule. Meso compound An optically inactive compound whose molecules are achiral even though they contain tetrahedral atoms with four different attached groups. A meso-compound is optically inactive due to internal compensation. Optically active substances Those substances which rotate the plane of polarisation of plane-polarised light when it is passed through their solutions are called optically active substances. This phenomenon is called optical activity. Plane of symmetry An imaginary plane that bisects a molecule in a way such that the two halves of the molecule are mirror images of each other. Any molecule with a plane of symmetry will be achiral. Plane-polarized light Ordinary light in which the oscillations of the electrical field occur only in one plane. It is obtained by passing a monochromatic light (light of single wavelength) through a Nicol prism. Polarimeter A device used for measuring optical activity. (R–S) System A method for designating the configuration of tetrahedral stereogenic centres. Racemic form (racemate or racemic mixture) An equimolar mixture of enantiomers. A racemic mixture is optically inactive due to external compensation. Racemisation The process of conversion of an enantiomer into racemic mixture is known as an racemisation. Retention If in an optically active molecule that relative configuration of the atoms groups around a chiral centre remains the same before and after the reaction, the reaction is said to proceed with retention of configuration. Relative configuration The relationship between the configuration of two chiral molecules. Molecules are said to have the same relative configuration when similar or identical groups in each occupy the same position in space. The configurations of molecules can be related to each other through reactions of known stereochemistry, for example, through reactions that cause no bonds to a stereogenic center to be broken. Resolution The process by which the enantiomers of a recemic form are separated. Ring flip The change in a cyclohexane ring (resulting from partial bond rotations) that converts one ring conformation to another. A chair-chair ring flip converts any equatorial substitutent to an axial substituent and vice versa.

592 Advance Theory in ORGANIC CHEMISTRY Ring strain The increased potential energy of the cyclic form of a molcule (usually measured by heats of combustion) when compared to its acyclic form. Specific rotation Specific rotation is defined as the number of degrees of rotation observed when the concentration of optically active substance is 1 g cm -3 and length of polarimeter tube is 1 decimetre (dm) for D-line of sodium vapour lamp at 25ºC. Stereogenic center An atom bearing group of such nature that an interchange of any two groups will produce a stereoisomer. Steric hindrance An effect on relative reaction rates caused when the spatial arrangement of atoms or groups at or near the reacting site hinders or retards a reaction. Torsional strain The strain associated with an eclipsed conformation of a molecule; it is caused by repulsions between the aligned electron pairs of the eclipsed bonds. (a) Aprotic Solvents O OO O CH3 CH3 CH2Cl2 O O S Dioxane N O H3C CH3 THF DMF CH3 Toluene Methylene Ethyl Acetone DMSO chloride ether bp (ºC) : 111 40 35 66 101 56 189 153 MATCHING LIST (2) 1. List-I List-II (P) Homologoues (Q) Duma’s method (1) May be constitutional isomers (R) Kjeldal’s method (S) Dimethyl ether & n-propyl ether (2) For estimation, Nitrogen collected as NH3 Codes: (3) For estimation, nitrogen collected as N2 P QRS (4) Differ by 14 amu in terms of molecular mass (A) 4 2 3 1 (*B) 4 3 2 1 (C) 1 3 2 4 (D) 1 2 3 4 Sol. (P) Homologous ¾® may be constitutional isomers (Q) Duma’s method ¾® nitrogen collected as N2 (R) Kjeldal method ¾® Nitrogen collected as NH3 (S) CH3 — O — CH3 and CH3CH2CH2 — OH ¾® differ by 14 amu. qqq