Question

Which of the following reactions will yield $2, 2$-dibromopropane ?

• A. $CH _{3}- CH = CH _{2}+ HBr$
• B. $CH _{3}- C \equiv CH +2 HBr$
• C. $CH _{3}- CH = CHBr + HBr$
• D. $CH \equiv CH +2 HBr$

Answer 1

Answer: (B)

Reaction of propyne with 2 molecules of HBr to form 2,2 -dibromo propane can be written as:
$
CH _{3}- C \equiv CH +2 HBr \rightarrow CH _{3}- C ( Br )= CH _{2}
$
$
CH _{3}- C ( Br )= CH _{2}+ HBr \rightarrow CH _{3}- C ( Br )_{2}- CH _{3}
$
The reaction follows Markownikoff's rule.