Question

Which of the following is the correct order of -I effect?

• A. $-\stackrel{+}{N}{H}_3>-CN>-OH>-N{H}_2$
• B. $-\stackrel{+}{N}{H}_3<-CN>-OH>-N{H}_2$
• C. $-\stackrel{+}{N}{H}_3<-CN<-OH>-N{H}_2$
• D. $-\stackrel{+}{N}{H}_3<-CN<-OH<-N{H}_2$

Answer 1

The correct option is A $-\stackrel{+}{N}{H}_3>-CN>-OH>-N{H}_2$

Inductive effect of $-\stackrel{+}{N}{H}_3$ is maximum due to presence of positive charge. Inductive effect of $-CN$ is more than $-OH$ and $-N{H}_2$ because of presence of triple bond between C and N. So more is the $\%$ of s-character. So it withdraws electron more powerfully towards itself.

Electron withdrawing group shows -I effect. Electron withdrawing group leads to development of ẟ+ on Carbon atom sharing a bond with the substituent as EWG pulled of electron towards it being more electronegative in nature. Among O and N, O is more electronegative than N. So inductive effect of $-OH>-N{H}_2$
Hence, the correct order of -I effect is $-\stackrel{+}{N}{H}_3>-CN>-OH>-N{H}_2$