Question

The option in which all the groups show electron donating nature when attached to a benzene ring are :

• A. $-N{O}_2,-Cl,-OH$
• B. $-OMe,-CN,-N{H}_2$
• C. $-NHCOC{H}_3,-Cl,-COOH$
• D. $-NHCOC{H}_3,-C{H}_3,-Br$

Answer 1

The correct option is D $-NHCOC{H}_3,-C{H}_3,-Br$

Electron donating group will increase the electron density on benzene ring and favours the electrophilic attack at ortho and para position. These groups are also called ortho-para directing group or activating group.

Electron withdrawing group will decrease the electron density at ortho and para position .
Thus, electrophilic attack occurs at meta position which has relatively higher electron density. Hence, these group are called meta directing or deactivating groups.

In (a),
$-N{O}_2$ Electron withdrawing group (-R and -I effect) so it is meta directing.
$-Cl$ and $-OH$ are both ortho/para directing

In (b),
$-CN$ Electron withdrawing group (-R and -I effect) so it is meta directing.
$-OMe$ and $-N{H}_2$ are both orthio/para directing
In (c),
$-COOH$- Electron withdrawing group (-R effect) so it is meta directing.
$-Cl$ and $-NHCOC{H}_3$ are both ortho/para directing

In (d), all the group are electron donating so they give predominantly ortho/para products
$-NHCOC{H}_3\to$ +R effect
$-C{H}_3\to$ +H effect
$-Br\to$ +R effect