Haloalkanes, Arenes, Haloarenes, Alcohols, Phenols, Ethers, and Epoxides — DU B.Sc (hons) Chemistry Previous Year Question Papers

Phenols, Ethers and Epoxides Attempt four questions in all. Q2 (a) For the reaction of 1-bromobutane with potassium tert-butoxide, predict whether Sn2 or E2 dominates. Justify your answer. (b) What happens when phenol reacts with chloroform in the presence of sodium hydroxide? Name the reaction and give the mechanism involved. (c) Substitution nucleophilic unimolecular proceeds with racemization along with some net inversion. Justify the statement. Q3. (a) o-Chlorotoluene reacts with potassium amide in liquid ammonia to yield a mixture of o-toluidine and m-toluidine. Explain giving mechanism. (b) Explain why nucleophilic substitution in aryl halides do not follow Sol or SN2 (c) Classify each of the following as aromatic, anti-aromatic and non-aromatic: Q4. (a) Explain substitution nucleophilic internal (SNi) mechanism with a suitable example. (b) Explain why halogens in aryl halides are ortho/para director but weak deactivator towards electrophilic substitution reactions. (c) Choose the correct option: (i) Primary alkyl halide in the presence of polar aprotic solvent and strong base would ideally undergo substitution nucleophilic _(unimolecular / bimolecular/ intramolecular/ aromatic). (ii) Grignard reagents will react with CO, to give_ _(aldehyde/ ketone/ carboxylic acid/ alcohol). (iii)The least reactive towards an Sul reaction would be _(benzyl chloride/ chlorobenzene/ t-butyl chloride/ allyl chloride). (iv) Primary, secondary and tertiary alcohols distinguished (Ferric chloride test/ Lucas test/ Tollen's test) (v) Pyridine is_ _(aromatic with 6t electrons/ anti-aromatic with 8t electrons/ aromatic with 8tt electrons/ non-aromatic 8л electrons) QS. Complete the following reactions: Q6. Write short notes on (any three): (ii) Pinacol-Pinacolone rearrangement (iv) Fries Rearrangement (5 x 3=15)