Question

Consider the following reactions. From these reactions which reaction will give carboxylic acid as a major product ?
(A) $R-C\equiv N \xrightarrow[\text{mild condition}]{(i)\ H^{+}/H_2O}$
(B) $R-MgX \xrightarrow[(ii)\ H_3O^{+}]{(i)\ CO_2}$
(C) $R-C\equiv N \xrightarrow[(ii)\ H_3O^{+}]{(i)\ SnCl_2/HCl}$
(D) $R\cdot CH_2\cdot OH \xrightarrow{PCC}$
(E)

Choose the correct answer from the options given below :

• A. A, B and E only
• B. A and D only
• C. B, C and E only
• D. B and E only

Hint:

Decide which of the reactions end in a carboxylic acid: nitrile partial hydrolysis, Grignard + CO2, Stephen, PCC, Rosenmund.

Answer 1

The Correct Option is D

(A) Partial hydrolysis of a nitrile under mild acidic conditions stops at the amide: not a carboxylic acid.
(B) Grignard reagent with $CO_2$ followed by $H_3O^+$ gives $RCOOH$: yes.
(C) $SnCl_2/HCl$ with the nitrile (Stephen reaction) gives an aldehyde: no.
(D) PCC oxidises a primary alcohol only to the aldehyde: no.
(E) Rosenmund reduction of benzoyl chloride gives benzaldehyde, which bromine water then oxidises to benzoic acid: yes.
B and E only: option (4).