Question

Which of the following reaction will take place at fastest rate?

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

Addition of $HBr$ takes place through formation of carbocation.
More the stability of carbocation, faster the rate of reaction.
Carbocation intermediates formed are :


Stability of carbocation intermediate:
$3^{\circ }>2^{\circ }>1^{\circ }$
Since in case (c) the carbocation formed is $3^{\circ }$ which is most stable, and hence the rate of reaction is the fastest in (c)