Question

Predict the major products of bromination of the following compounds, using Br₂ and FeBr₃ in the dark.

(a)

(b)

(c)

Short answer

(a)

(b)

(c)

Step-by-step solution

Bromination

Bromination is a kind of electrophilic aromatic substitution reaction. A hydrogen atom is substituted by a bromine atom. The formation of Br⁺ ion is not favorable and thus presence of a Lewis acid like FeBr₃ is necessary.

Since all electrophilic aromatic substitution occurs through the formation of carbocation intermediate, presence of electron donating group favors the reaction.

Major product formed from bromination of compound (a)

The major product formed after bromination of the given compound is shown below. The substitution takes place ortho to the methoxy group. The carbocation intermediate formed is stabilized by electron donation by the methoxy group.

Major product formed from bromination of compound (b)

The major product formed after bromination of the given compound is shown below. The substitution takes place ortho to the methyl group. The (+I) effect of the methyl group stabilizes the carbocation intermediate formed.

Major product formed from bromination of compound (c).

The major product formed after bromination of the given compound is shown below. The methoxy group is an electron donating group. The substitution takes place at the ortho position of the methoxy group.