91Ó°ÊÓ

(a) When p-methyl benzoic acid is treated with $LiA{H}_4 \mathrm{and} \mathrm{then} \mathrm{with}\mathit{} H_3{O}^{+}$ the carboxyl group is reduced to a primary alcohol group. The product obtained is p-methyl-benzyl alcohol.

(b) When p-methyl benzoic acid is treated with N-bromosuccinimide in $CC{l}_4$, a bromine atom gets substituted in the benzyl carbon. The product obtained is p-bromomethylbenzoic acid.

(c) When p-methyl benzoic acid is treated with $C{H}_{3}MgBr\mathit{} \mathrm{and} \mathrm{then} \mathrm{with} H_3{O}^{+}$the methyl anion in the Grignard reagent picks up a proton from the acid to obtain a product called methane.

(d) When p-methyl benzoic acid is treated with $KMn{O}_4$in the presence of $H_3{O}^{+}$the methyl group in the p-position is oxidized to acid. The product obtained is benzene-1,4-dicarboxylic acid.