Question

Decreasing order of $-I$ power of given groups is:
(a) $CN$
(b) $N{O}_2$
(c) $\stackrel{+}{N{H}_3}$
(d) $F$

• A. $b>a>d>c$
• B. $b>c>d>a$
• C. $c>b>d>a$
• D. $c>b>a>d$

Answer 1

Answer: (D)

$N{H}_3^{+}$ is most stronger electron withdrawing since it is electron deficient and carrying a positive charge. Nitro group is also an electron withdrawing group. $CN-$ is more withdrawing group than $F-$ because fluorine being smaller in size, is already carrying a negative charge and cannot withdraw any more electrons.