Question

Which of the following represents the correct increasing order of electron pair availability on nitrogen based on hyperconjugation and+ I and -I effects arising from alkyl groups ?

• A. iv < iii < ii < i
• B. iv < i < iii < ii
• C. i < ii < iii < iv
• D. i < iv < iii < ii

Answer 1

The correct option is D i < iv < iii < ii

Since alkyl groups are electron donating and the + I effect Of alkyl ,groups on a saturated carbon chain follows,the order
$(C{H}_3{)}_{3}C\to (C{H}_3{)}_{2}CH\to C{H}_{3}C{H}_2\to C{H}_3-$
However, when alkyl, group is attached ix benzene ring, the order of + I effect is reversed and known as hyperconjugatiot effect
$C{H}_3>-C{H}_{3}C{H}_2>(C{H}_3{)}_{2}CH\to (C{H}_3{)}_{3}C-$
Thus, alkyl groups release electrons and increase the basic strength of aniline in the following order