Question

Which of the following is not an example of $+I$ group?

• A. $-CN$
• B. $-N{H}^{-}$
• C. $-C{H}_2^{-}$
• D. $-C{H}_3$

Answer 1

The correct option is A $-CN$

$\text{Electron donating groups( EDG )}-N{H}^{-},-C{H}_3,-C{H}_2^{-}$ shows +I effect. The order of +I group is
$-C{H}_2^{-}>-N{H}^{-}>-C{H}_3>-CN$. Among these three $-C{H}_2^{-}$ and $-N{H}^{-}$ have more +I effect due to presence of negative charge as compared to $-C{H}_3$
More electronegativity of atom means more tendency to hold electrons on itself.
Electron withdrawing groups( EWG ) shows -I effect. It withdraws electron more powerfully towards
itself.

So option(a) is the correct answer.