Question

When nitrobenzene is treated with $B{r}_2$ in presence of $FeB{r}_3$, the major product formed is $m-$ bromonitrobenzene. Statements which are related to the formation of $m-$isomer are:

• A. The electron density on meta carbon is more than that on ortho and para positions
• B. The intermidiate carbonium ion formed after initial atack of $B{r}^{+}$ at the meta position is least destabilised
• C. Loss of aromaticity when $B{r}^{+}$ attacks at the ortho and para positions and not at meta position
• D. Easier loss of $H^{+}$ to regain aromaticity from the meta position than from ortho and para positions

Answer 1

Answer: (A), (B)

The intermidiate carbonium ion formed after initial atack of $B{r}^{+}$ at the meta position is least destabilised



Electron withdrawing groups such as $-N{O}_2$ group decrease electron density at the ortho and para-positions, thus in such cases meta positions will has relatively higher electron density than the ortho and para positions.




Meta substitution will not put the positive charge on the same carbon that bears the nitro group. Hence, the intermidiate carbonium ion formed after initial atack of $B{r}^{+}$ at the meta position is least destabilised.