Question

Which of the following compound does not react with concentrated alkali to give corresponding alcohol and salt of carboxylic acid ?

• A. Trimethyl acetaldehyde
• B. Benzaldehyde
• C. Dimethyl acetaldehyde
• D. Formaldehyde

Answer 1

The correct option is C Dimethyl acetaldehyde

Aldehydes lacking a-hydrogen atom react with concentrated alkali to give corresponding alcohol and salt of carboxylic acid. This is Cannizaro reaction.
The structures of the given aldehydes are as follows
(a) $(C{H}_3{)}_3\cdot C-CHO$

trimethyl acetaldehyde has no $\alpha$ -hydrogen

(b) (Refer image) Benzaldehyde gives Cannizzaro reaction because it has no $\alpha -H$

(c) $\underset{Dimethylacetaldehyde}{(C{H}_3{)}_2\stackrel{\alpha hydrogen}{CHCHO}}$
(d) $\underset{formaldehyde}{\underset{no\alpha -hydrogen}{\underset{\uparrow }{HCHO}}}$

Thus, among the given compounds, dimethylacetaldehyde is the aldehyde which does not produce corresponding alcohol and salt of carboxylic acid when treated with concentrated alkali because of the presence of a-hydrogen atom.