# What is the most likely product to form when 4-methyl-1-pentene reacts with excess Br2? Please show the structural formula. What type of reaction is this?

Jun 21, 2018

The most likely product is 1,2-dibromo-4-methylpentane.

#### Explanation:

The reaction of an alkene with bromine gives a vicinal dibromide (a 1,2-dibromide).

Thus, the reaction of bromine with 4-methylpent-1-ene gives 1,2-dibromo-4-methylpentane.

The mechanism

The electrons in the π bond of the approaching alkene induce a dipole in the highly polarizable $\text{Br-Br}$ bond.

The π electrons attack the partially positive $\text{Br}$ atom, displacing a bromide ion.

The $\text{Br}$ atom then joins to the other alkene carbon and forms a cyclic bromonium ion.

In a second step, the $\text{Br"^"-}$ attacks the more substituted carbon of the bromonium ion, forming a 1,2-dibromoalkane.

This reaction is an example of electrophilic addition to an alkene.