Question

Which of the following statements are correct for benzoic acid ?

• A. Nitration gives o-and p-nitrobenzoic acid.
• B. Bromination ($B{r}_2/FeB{r}_3$) gives m-bromobenzoic acid.
• C. The Friedel-Crafts reaction with $C{H}_{3}COCl/AlC{l}_3$ gives m-carboxyacetophenone.
• D. The reaction with concentrated sulphuric acid gives 3-carboxybenzenesulphonic acid.

Answer 1

Answer: (B), (D)

The correct options are
B The reaction with concentrated sulphuric acid gives 3-carboxybenzenesulphonic acid.
D Bromination ($B{r}_2/FeB{r}_3$) gives m-bromobenzoic acid.

A. The substituent $COOH$ on benzene ring is meta directing which directs the incoming group to meta position. Thus the nitration of benzoic acid produces m-nitrobenzene.

B. Bromination of benzoic acid gives m-bromobenzoic acid, as shown in reaction above.

C. Friedel-Crafts reaction involves the attack by an electrophile to the substituted benzene ring. Benzoic acid does not undergo Friedel-Crafts reaction because the carboxyl group is strongly deactivating.

D. Reaction of benzoic acid with concentrated $H_{2}S{O}_4$ leads to sulfonation of the aromatic ring, in which the functional group $S{O}_{3}H$ replaces a hydrogen atom on the aromatic ring. The product is mostly meta-sulfobenzoic acid. See reaction above.