Give reasons for the following. (i) Carboxylic acids do not give characteristic reactions of carboxyl group (ii) Treatment of benzaldehyde with HCN gives a mixture of two isomers which cannot be separated even by careful fractional distillation. (iii) Sodium bisulphite is used for the purification of aldehydes and ketones.

Give reasons for the following. (i) Carboxylic acids do not give chara

1.	Give reasons for the following. (i) Carboxylic acids do not give characteristic reactions of carboxyl group (ii) Treatment of benzaldehyde with HCN gives a mixture of two isomers which cannot be separated even by careful fractional distillation. (iii) Sodium bisulphite is used for the purification of aldehydes and ketones.
Answer» SOLUTION : (i) It is due to reasonance (ii) It is BECAUSEWE get two opticalisomers which have same physical properties , THEREFORE , cannot be separated by fractional distillation . Aldehydesand ketones from addition compound with `NaHSO_3` whereasany impurities do not. On hydrolysis , we getpure aldehydes and ketonesback again . `CH_3- oversetunderset(\|\|)(O)(C ) -H - NaHSO_3 to CH_3 - oversetunderset(\|)(OH)(C )H - SO_3 NA overset(H_2O //H^(+) )(to) CH_3- oversetunderset(\|\|)(O)(C ) - H + NaHSO_3`