Question

What are the major and minor products obtained in the reaction of (E)-3-methyl-2-pentene and HBr?

Answer 1

The major product by far is 3-bromo-3-methylpentane; there may be a small amount of 2-methyl-3-bromopentane.

Explanation:

The structure of (`E`)-3-methylpent-2-ene is

According to Markovnikov's rule, the `"H"^+` from `"HBr"` will add to `"C-2"` of the alkene and form a 3° carbocation at `"C-3"`.

The `"Br"^-` will add to `"C-3"` and form 3-bromo-3-methylpentane

There may be a small amount of product formed when the `"H"^+` adds to `"C-3"` of the alkene to form the less stable 2° carbocation at `"C-2"`.

The `"Br"^-` will then add to `"C-2"` and form 2-bromo-3-methylpentane.