Question

4 -nitrotoluene is treated with bromine to get compound ' $P$ ' which is reduced with Sn and HCl to get compound ' $Q$ ' ' 'Q ' is diazotised and the product is treated with phosphinic acid to get compound ' $R$ ' ' $R$ ' is oxidised with alkaline solutionKMnO $_{4_{1}}$ to get the final product. Identify the finăl product.

• A. $2$-Bromo-$4$-hydroxybenzoic acid
• B. Benzoic acid
• C. $4$-Bromobenzoic acid
• D. $3$-Bromobenzoic acid
• E. $2$-Bromobenzoic acid

Answer 1

Answer: (E)

Given,

Step 1.

($\because NO _{2}.$ is $m$ -directing group while $CH _{3}$ group iso $-$ and $p$ - directing group. Thus, Br group attach at o-position with respect to $CH _{3}$ and $m$ -position with respect to $NO _{2}$ group)

Step 2. On reduction with $Sn / HCl , NO _{2}-$ group changes to $- NH _{2}$ group.



Step 3. On treatment with

$NaNO _{2}+ HCl ; NH _{2}$ changes to diazo group (i.e. $Q$

shows diazotisation).



Step 4. On treatment with $H _{3} PO _{2}$, only diazo group $\left( N _{2} Cl \right)$ reacts and gets removed



Step 5. On oxidation with $KMnO _{4} / OH ^{-}- CH _{3}$ group changes to $-$ COOH group.