Question

Which one of the following functional groups is not meta directing?

• A. $-\mathrm{COOH}$
• B. $-\mathrm{NO}{}_2$
• C. $-\mathrm{CHO}$
• D. $-\mathrm{OCH}{}_3$

Answer 1

Answer: (D)

The group which contain double bond in its structure and have more electronegative element bonded with the atom (which is bonded with the $C$-atom of benzene ring) gives m-directing products and those do not have double bond and have lone pair electron over the atom, (which is bonded with the benzene ring) do not give $m$-directing product (they give $o$ and $p$- products).

(a) $-COOH$ group, contains double bond in its structure and $-$ C-atom, which is bonded with the ring has more electronegative oxygen atom bonded with it. i.e.

$\left[-\underset{\stackrel{||}{O}}{C}-OH\right]$

$\therefore$ It gives $m$- directing product.

(b) $-N{O}_2$ group, contains double bond in its structure and $N$ -atom, which is bonded with the ring has more electronegative oxygen atom bonded with it. i.e.



$\therefore$ It gives $m$ -directing product.

(c)$-CHO$ group also contains double bond in its structure and $C$ -atom, which is bonded with the ring has more electronegative oxygen atom bonded with it. i.e.

$\left[-\underset{\stackrel{||}{O}}{C}-OH\right]$

$\therefore$ It gives $m$ -directing product.

(d) $-O-C{H}_3$ group, has no double bond in its structure and $O$-atom, which is bonded with the ring has less electronegative $C$ -atom, bonded with it. i.e.



Thus, it does not give $m$ - directing product.