CHEMICAL TEST OF ORGANIC COMPOUNDS

CHEMICAL TEST OF ORGANIC COMPOUNDS Identification Test

ALKANE 1) Halogenation of Alkane with Br2 in uv Observation: Brown turns to colourless. General Equation: R–Br + HBr R–H + Br2 uv

ALKENE 1) Halogenation of Alkene with Br2 in Inert Solvent (CCl4 or CH2Cl2) Observation: Brown color turns to colorless. General equation: CC + Br2 CCl4 CC RoomDatrekmperature Br Br Dark

ALKENE 2) Reaction of alkene with basic, dilute, cold KMnO4  Baeyer’s test C C + KMnO4 OH-, cold CC + MnO2 (purple) dilute (brown precipitate) OH OH 1,2-diols @ glycols Observation: Purple color of KMnO4 decolorized and brown precipitate formed.

ALKENE 3) Reactions of alkene with hot, acidified, concentrated KMnO4 R1 R3 R1 R3 C=C KMnO4(conc), C=O + O=C H+, heat R2 R2 H H [O] R3 Observation: O=C Purple color of KMnO4 decolorized. OH

ARENE 1) Reactions of Alkylbenzene with Br2 in uv General equation: R RX X2, uv Observation: Brown colour of Br 2 turns to colourless.

ARENE 3) Reactions of Alkylbenzene with KMnO4, H+, ∆ General equation: Observation: Purple color of KMnO4 decolorized.

ALCOHOL 1) Reactions of R-OH with Na General equation: RO-H + Na → RO-Na + ½H2 Observation: Gas released can produce a ‘pop’ sound when tested with wooden splinter.

ALCOHOL 2) Lucas's reagent, HCl(conc.), ZnCl2 (to differentiate between 1, 2 and 3 alcohol) Examples:

ALCOHOL 2) Lucas's reagent, HCl(conc.), ZnCl2 (to differentiate between 1, 2 and 3 alcohol) Classes of Observation alcohol The solution does not turn cloudy Primary, The solution turn cloudy within 5 1°ROH minutes Secondary, The solution turn cloudy 2°ROH immediately Tertiary, 3°ROH

ALCOHOL 3) Reactions of R-OH with PCl5 @ SOCl2 General equation: R-OH + PCl5 → R-Cl + PCl3 + HCl R-OH + SOCl2 → R-Cl + SO2 + HCl Observation: Acidic white fumes is released.

ALCOHOL 4) KMnO4/H+ or K2Cr2O7 /H+ (to differentiate between 1 and 3 or 2 and 3 alcohols) General equation:

ALCOHOL 4) KMnO4/H+ or K2Cr2O7 /H+ (to differentiate between 1 and 3 or 2 and 3 alcohols) Class of alcohol and observation Primary, 1° KMnO4  Purple turns to colorless K2Cr2O7  Orange turns to green Secondary, 2° (Same observation as for primary ROH) Tertiary, 3° (The color of oxidizing agent is remains)

ALCOHOL 5) Reactions of R-OH with I2, NaOH (Iodoform test) for alcohol with methyl hydroxy group YELLOW PRECIPITATE

ALCOHOL 6) Reaction of alcohol with carboxylic acid, H2SO4 (conc.), Δ (Esterification) General equation: OO H+ C OR' + H2O ⇌R C OH + H—OR’ R ester Δcarboxylic acid alcohol Observation: Sweet fruity smell is formed.

PHENOL 1) Reactions with NaOH (to differentiate phenol with aliphatic alcohol) General equation: C6H5-OH + NaOH C6H5-O-Na+ + H2O Phenol (soluble in water) Observation: One layer of solution formed R-OH + NaOH 2 layers solutions formed aliphatic alcohol (insoluble in water)

PHENOL 2) Reactions with Br2 in H2O General equation: OH OH Br2/H2O Br Br Br 2,4,6-tribromophenol Observation: Brown color of Br 2 turns to colorless and white precipitate is forms

PHENOL 3) Reactions with FeCl3 (Phenol Test) General equation: OH OH + FeCl3 FeCl3 Observation: Turn the yellow FeCl3 into purple complex.

PHENOL 4) Reactions with HNO3 (conc.) General equation: OH OH concentrated O2N NO2 HNO3 NO2 2,4,6-trinitrophenol Observation: Yellow precipitate formed.

KETONE/ ALDEHYDE 1) Brady’s Reagent; 2,4 – dinitrophenylhydrazine (2,4-DNPH) Observation: Yellow precipitate / Orange crystal formed for aliphatic compound.

KETONE/ALDEHYDE 2) Reactions of carbonyl with I2, NaOH (Iodoform test) for aldehyde and ketone with methyl carbonyl group General equation: YELLOW PRECIPITATE Observation: Yellow precipitate formed.

ALDEHYDE ONLY 1) Oxidation with KMnO4 @K2Cr2O7 General equation: O O RC OH [O] RCH Observation: KMnO4 : Purple to colourless K2Cr2O7 : Orange to green

ALDEHYDE 2) Tollens’ Reagent; Ag(NH3)2+, OH-, ∆ General equation: R O + 2[Ag(NH3)2]+ OH- O C R C O-  + 2Ag + 4NH3 + 2H2O H silver mirror Observation: Silver mirror formed on the wall of the tube.

ALDEHYDE 3) Fehling’s/Benedict’s Reagent; Cu2+, OH-, ∆ R C O + Cu2+ O H Fehlings' Solution R C O- + Cu2O + H2O Copper(I) Oxide (Brick red precipitate) Observation: Blue color turns to brick red precipitate.

ALDEHYDE 3) Schiff’s Reagent Observation: Pinkish purple color solution is formed.

CARBOXYLIC ACID 1) Reaction of carboxylic acid with alcohol, H2SO4 (conc.), Δ (Esterification) General equation: OO H+ C OR' + H2O ⇌R C OH + H—OR’ R ester Δcarboxylic acid alcohol Observation: Sweet fruity smell is formed.

CARBOXYLIC ACID 2)Reaction with Reactive Metals Na @ Mg General equation: Observation: H2 gas released can be tested with wooden splinter to produce ‘pop’ sounds.

CARBOXYLIC ACID 3) Reaction with metal carbonates; Na2CO3 @ MgCO3 @ NaHCO3 Observation: Gas released turns the lime water cloudy.

CARBOXYLIC ACID 4) Reaction with PCl5 @ SOCl2 O PCl5 R C Cl+ POCl3 + HCl O C O R OH SOCl2 R C Cl + SO2 + HCl Observation: White acidic fumes is releases.

AMINE 1) Reaction of aniline with Br2 in H2O General equation: NH2 Br NH2 + 3HBr 3BBr2r,2H(a2qO) Br room temperature Br Observation: Brown color of Br2 decolorized and white precipitate is formed.

AMINE 2) Reaction with Nitrous Acid; HONO @ HNO2, cold @ NaNO2, HCl, cold +HCl NaNO2 +HONO NaCl Class of Amine OBSERVATION 1° aliphatic amine Bubbles gas (N2 gas) when temperature 0 - 5°C) 2° aliphatic amine Yellow oil 3° aliphatic amine Clear solution (soluble salt formed) 1° aromatic amine No bubble gas when the temperature is below 5°C 2° aromatic amine Yellow oil 3° aromatic amine Yellow precipitate



AMIINE (a) Primary aliphatic amines RCH 2CH2 NH 2 + NaNO2 ⎯H⎯⎯Cl→RCH 2CH 2 + - Cl  N2 RCH = CH2 - H+  2 + H 2  + N 2 +H2O RCH  C +X- RCH 2CH 2OH RCH 2CH 2Cl Observation : Formation of gas bubbles (N2)

AMINE (b) Secondary aliphatic amines Secondary aliphatic amines reacts with nitrous acid to form secondary N-nitrosamines as yellow oil which is stable under the reaction conditions. (yellow oil) R2NH NaNO2, HCl R +NaCl H2O R NNO + cold secondary N-nitrosoamines Observation: Formation yellow oil

AMINE (c) Tertiary aliphatic amines When a tertiary aliphatic amine is mixed with nitrous acid, an equilibrium is established among the tertiary amine, its salt, and an N- nitrosoammonium salt. NaNO2, HCl +2R3N R3N N OCl R3NHCl cold Water soluble salt Observation : Clear solution is formed.

AMINE (d) Primary aromatic amines Primary aromatic amines react with nitrous acid to give benzenediazonium salts. NH2 N2+Cl- NaNO2, HCl + NaCl + H2O Becloowld5°C baernezneendeiadziaoznoinuimumsasltalt Observation: No gas bubbles if the temperature is below 5°C

AMINE (e) Secondary aromatic amines Secondary aromatic amines react similar to secondary aliphatic amines. CRH3 NaNO2, HCl CRH3 NH N NO below 5 oC N-Methyl-N-nitrosoaniline (yellow oil) Observation: Yellow oil is formed.

AMINE (f) Tertiary aromatic amines Tertiary aromatic amines undergo substitution at the para position of the ring to from nitrosoaniline. CRH3 CRH3 N NaNO2, HCl O N N CRH3 CRH3 below 5 oC N,N-Dimethyl-4-nitrosoaniline (precipitate) Observation: Yellow precipitate is formed.

AMINE 3) Hinsberg’s Test (to differentiate between 1°2°and 3°amines i. Benzenesulphonyl chloride ii. Base – KOH iii. Acid – HCl Class of amine After KOH is After HCl is added added 1° amine Clear solution Precipitate form 2° amine Precipitate form Precipitate 3° amine No change remain Clear solution