What is the major product of the addition reaction below?

#CH_3CH_2CH_2CH=CH_2 + HBr ->#

1 Answer
Jun 24, 2016

#"2-bromopentane"#

Explanation:

The electron-rich olefin adds to the electrophile, the protium ion, as a first step in the reaction:

#RCH=CH_2 + HBr rarr RC^(+)HCH_3 + Br^-#

The second step is of course bond formation between nucleophilic #Br^-# and the carbocation to form the 2-substituted alkane. The #2""^@# carbocation as shown is stabilized with respect to the #1""^@# carbocation, #RCH_2-CH_2^+#, and the reaction tends to proceed thru this more stable intermediate. This is classic Markownikow addtion.