Question

When 3-methylbutan-2-ol is treated with HBr, the following reaction takes

place:

Give a mechanism for this reaction.

(Hint : The secondary carbocation formed in step II rearranges to a more

stable tertiary carbocation by a hydride ion shift from 3rd carbon atom.

Answer 1

The mechanism of the given reaction involves the following steps:

Step 1: Protonation

Step 2: Formation of 2° carbocation by the elimination of a water molecule

Step 3: Re-arrangement by the hydride-ion shift

Step 4: Nucleophilic attack