The additon of HBr to 2-pentene gives

Options

A. 2-bromopentane only
B. 3-bromopentane only
C. 2-bromopentane and 3-bromopentane
D. 1-bromopentane and 3-bromopentane

Answer

C

Explanation

Addition of a proton to 2-pentene can give two carbocations (I and II)

which are almost equally stable since carbocation (I) is stabilized by five (3+2) hyperconjugation structures and carbocation (II) is stabilized by four (2+2) hyperconjugation structures . Therefore , nucleophilic attack on these gives the coresponding bromoalkanes in almost equal amounts . Of course , the yield of 2-bromopentane will be slightly more than that of 3-bromopentane.