Question #c71e7

1 Answer
Sep 6, 2017

(B) is the least stable carbocation.

Explanation:

The general order of stability of cations is

#"R"_3"C"^"+" > "C"_6"H"_5"-CH"_2^"+" > "CH"_2"=CH-CH"_2^"+" > "R"_2"CH"^"+" > "RCH"_2^"+" >color(white)(ml) "CH"_3^"+"#
#color(blue)(color(white)(m)3° >color(white)(ll) " benzyl"color(white)(ml)> color(white)(mmm)"allyl"color(white)(mmll)>color(white)(m)2° color(white)(m)>color(white)(m)1°color(white)(m)>color(white)(m)"methyl""#

(C) is a 3° carbocation, so it is the most stable.

(D) is a benzylic carbocation, so it is less stable.

(A) is an allylic carbocation, so it is third in stability.

(B) is a 2° carbocation, so it is the least stable.