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

Trichloroacetaldehyde

The correct answer is (1) trichloroacetaldehyde.

DDT is produced by the reaction of chlorobenzene with chloral (trichloroacetaldehyde) in the presence of concentrated sulfuric acid. The reaction is shown below:

The other options are incorrect. Option (2) m-chloroacetaldehyde, is not a trichloroacetaldehyde and will not react with chlorobenzene to produce DDT. Option (3) acetaldehyde, is not a trichloroacetaldehyde and will not react with chlorobenzene to produce DDT. Option (4) nitrobenzene, is not a halogenated compound and will not react with chlorobenzene to produce DDT.