Question

Write the name of the major organic product formed in the reaction of 1-pentene with HBr.

• A. 1-bromopentane
• B. 2-bromopentane
• C. 3-bromopentane
• D. None of these

Answer 1

Answer: (B)

2-bromopentane

1-pentene reacts with hydrogen bromide to form 2-bromopentane. This is an example of the electrophilic addition reaction. The addition occurs according to Markownikoff's rule; the negative part $\left(C{l}^{-}\right)$ of the reagent goes to the more substituted carbon atom.

$C{H}_2=CHC{H}_{2}C{H}_{2}C{H}_3+HBr\to C{H}_{3}CHBr-C{H}_{2}C{H}_{2}C{H}_3$

Hence, the correct option is B.