Question

In the mechanism for the reaction of HBr with t-butyl alcohol, pick out the correct statement.

• A. Formation of protonated alcohol in a slow step
• B. Formation of $\left( CH _{3}\right)_{3} C ^{+}$ is a slow step
• C. Formation of $\left( CH _{3}\right)_{3} CBr$ from $\left( CH _{3}\right)_{3} C ^{+}$ is a slow step
• D. Formation of $\left( CH _{3}\right)_{3} C ^{+}$ is a fast step

Answer 1

Answer: (B)

The mechanism of this reaction is as follows

$\left( CH _{3}\right)_{3} COH + HBr \rightleftharpoons\left( CH _{3}\right)_{3} COH _{2}+ Br ^{-}$ (fast)



Hence, formation on carbocation $\left( CH _{3}\right)_{3} C ^{+}$ is slow step (R.D.S.).