Question

Choose the correct statement(s) for the following compounds

• A. $+M$ effect of $-N{H}_2$ operates at ortho, para and meta positions.
• B. $-C{H}_3$ group increases the electron density at ortho and para positions due to Hyperconjugation $\left(H\right)$ effect.
• C. $-N{H}_2$ group increases the electron density at ortho and para positions and is called an activating group.
• D. $-C{H}_3$ group increases the electron density at ortho and para positions due to mesomeric $\left(M\right)$ effect.

Answer 1

Answer: (B), (C)

The correct options are
B $-C{H}_3$ group increases the electron density at ortho and para positions due to Hyperconjugation $\left(H\right)$ effect.
C $-N{H}_2$ group increases the electron density at ortho and para positions and is called an activating group.

$-N{H}_2$ group shows $+M$ effect. It is called an activating group because it increases the electron density at ortho and para position as shown :


Both M effect and H effect will operate only at ortho/para positions and not at meta positions.
Hyperconjugation in $C_6{H}_{5}C{H}_3$:


Note: The effect due to hypergonjugation is generally less dominating than mesomeric effect, but more dominating than inductive effect.