Which of the following compound reacts with chlorobenzene to produce DDT?

Trichloroacetaldehyde

The correct answer is option 4. Trichloroacetaldehyde.

DDT is produced by the reaction of chlorobenzene with trichloroacetaldehyde in the presence of a catalyst, such as anhydrous \(AlCl_3\). The reaction proceeds through a Friedel-Crafts acylation reaction.

The reaction is illustrated below:

DDT is a colorless, odorless, tasteless solid with a melting point of 109.5°C. It is a very effective insecticide, but it is also highly toxic to humans and other animals.

The other options are incorrect.

Option (1), acetaldehyde, does not react with chlorobenzene to produce DDT.

Option (2), nitrobenzene, does not react with chlorobenzene to produce DDT.

Option (3), m-chlorobenzaldehyde, does not react with chlorobenzene to produce DDT.