Question

Besides vanillin, other fragrant aromatic compounds include anisaldehyde, cinnamaldehyde, and coumarin. How would you predict where bromination would take place in these structures?

Answer 1

Here's how I would argue.

Explanation:

Anisaldehyde

The structure of anisaldehyde is

The aldehyde group directs substituents to the meta positions (`"C3 and C5"`).

The methoxy group also directs substituents to the ortho positions (`"C3 and C5"`).

∴ The bromination product is 3-bromo-4-methoxybenzaldehyde.

Cinnamaldehyde

The structure of cinnamaldehyde is

The `"C=C"` double bond in the side-chain is more reactive than the benzene ring.

Hence, we will get addition across the external bond.

The bromination product is 2,3-dibromo-3-phenylpropanal.

Coumarin

The structure of coumarin is

The alkene double bond is more reactive than those in the benzene ring.

∴ We will get addition of bromine across the double bond.

The product will be 3,4-dibromocoumarin.