Question

when 3-methylbutan-2-ol is treated with HBr, the following reaction takes place:

Give the mechanism of this reaction.
Hint : The secondary carbocation formed in step II rearranges to a more stable tetriary carbocation by a hydride ion shift form the third carbon atom.

Answer 1

The protonation of given alcohol followed by loss of water gives a `2^(@)` carbocation (I), which being unstable rearranges by 1,2-hydride shift to form a more stable `3^(@)` carbocation (II). Nuclueophilic attack by `Br^(-)` ion on this carbocation (II) gives the final product.