Dichloroacetaldehyde

Dichloroacetaldehyde is a chlorinated aldehyde with the chemical formula HCCl2CHO. Along with monochloroacetaldehyde and trichloroacetaldehyde, it is one of the three possible chlorinated acetaldehydes.

Properties and reactions
Dichloroacetaldehyde is a highly volatile liquid that is easily soluble in water to form Hydrates. A geminal diol, also known as monohydrate, 2,2-dichloro-1,1-ethanediol, is formed in water.
 * Dichloroacetaldehyde reaction01.svg

The compound decomposes when heated. In the presence of Lewis acids such as antimony trichloride, iron(III) chloride, aluminum trichloride, tin(IV) chloride or boron trifluoride, the trimer hexachloroparaldehyde (2,4,6-tris(dichloromethyl)-1,3,5-trioxane) can be obtained. The trimer forms colourless crystals that melt at 131–132 °C. At the boiling point of 210–220 °C, dichloroacetaldehyde decomposes.
 * Dichloroacetaldehyde reaction02.svg

Reduction with lithium aluminium hydride gives dichloroethanol.

Uses
Dichloroacetaldehyde is used to produce other chemical compounds such as mitotane. Condensation with chlorobenzene yields p,p′-dichloro-1,1-diphenyl-2,2-dichloroethane, which was previously used as an insecticide:
 * [[File:Synthesis Dichlorodiphenyldichloroethane.svg]]

Synthesis
Dichloroacetaldehyde can be obtained by chlorinating acetaldehyde or paraldehyde. Hypochlorination of 1,2-dichloroethylene using chlorine and water produces pure dichloroacetaldehyde.