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

Give reasons for the following : (a) Carboxylic acids do not give cha

1.	Give reasons for the following : (a) Carboxylic acids do not give characteristic reactions of carbonyl group. (b) Treatment of benzaldehyde with HCN gives a mixture of two isomers which cannot be separated even by careful fractional distillation. (c) Sodium bisulphite is used for the purification of aldehydes and ketones.
Answer» SOLUTION :(a) Due to resonance, the position of carbonyl group is changing. Hence, carboxylic ACIDS do not give REACTIONS of carbonyl group. (b) It is because we get two optical isomers which have same physical properties. Therefore they cannot be separated by fractional distillation. (c) Aldehydes and ketones form addition COMPOUNDS with `NaHSO_3` whereas impurities do not. On hydrolysis, we get pure aldehydes and ketones back. `CH_(3)-overset(O)overset(\|\|)C-H + NaHSO_(3) to CH_(3) - overset(OH)overset(\|)CH-SO_(3)Na overset((H_(2)O)//H)to CH_(3)-overset(O)overset(\|\|)C-H + NaHSO_(3)`