Q. The correct order of increasing stabilities for the following carbocations is
(1) allyl carbocation
(2) neopentyl carbocation
(3) benzyl carbocation
(4) isobutyl carbocation

 4339  181 J & K CETJ & K CET 2016Organic Chemistry – Some Basic Principles and Techniques Report Error

Solution:

Allyl carbocation (stabilised by resonance)
image
Neopentyl carbocation :
image
Benzyl carbocation (stabilised by resonance)
image
Isobutyl carbocation :
image
Benzyl and allyl carbocations are much more stable due to resonance
Hence, the stability order is
Neopentyl carbocation isobutyl carbocation allyl carbocation benzyl carbocation