Question

A compound (A) with molecular formula C\(_4\)H\(_9\)N on reduction with DIBAL-H followed by hydrolysis, gives a compound (B). Compound (B) gives positive Tollens’ test but does not give iodoform test. Compound (B) can also be obtained when ethanal is treated with dilute NaOH followed by heating. Identify (A) and (B). Write the reactions of (A) with DIBAL-H followed by hydrolysis.

Hint:

DIBAL-H is a selective reducing agent, typically used for reducing amides to aldehydes, while hydrolysis converts them to their corresponding carboxylic acids.

Answer 1

Based on the information, we can identify compound (A) as butanamide (C\(_4\)H\(_9\)N) because it undergoes reduction with DIBAL-H to form an aldehyde (B). The fact that (B) gives a positive Tollens' test indicates that it is an aldehyde. The negative iodoform test suggests that (B) is not a methyl ketone. Based on the information that (B) can also be formed by treating ethanal (acetaldehyde) with NaOH, we can conclude that (B) is ethanal.
Reactions:
The reaction of butanamide (A) with DIBAL-H followed by hydrolysis can be represented as follows: \[ \text{Butanamide} \xrightarrow{\text{DIBAL-H}} \text{Butanal} \xrightarrow{\text{H}_2\text{O}} \text{Ethanal (B)} \]