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Benzal chloride

Benzal chloride is an organic compound with the formula C<sub>6</sub>H<sub>5</sub>CHCl<sub>2</sub>. This colourless liquid is a lachrymator and is used as a building block in organic synthesis.

Preparation and usage

Benzal chloride is produced by the free radical chlorination of toluene, being preceded in the process by benzyl chloride (C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>Cl) and followed by benzotrichloride (C<sub>6</sub>H<sub>5</sub>CCl<sub>3</sub>):

C<sub>6</sub>H<sub>5</sub>CH<sub>3</sub> + Cl<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>Cl + HCl
C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>Cl + Cl<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>CHCl<sub>2</sub> + HCl
C<sub>6</sub>H<sub>5</sub>CHCl<sub>2</sub> + Cl<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>CCl<sub>3</sub> + HCl

Benzylic halides are typically strong alkylating agents, and for this reason benzal chloride is treated as a hazardous compound.

Treatment of benzal chloride with sodium gives stilbene.

The main industrial use is as a precursor to benzaldehyde. This conversion involves hydrolysis in the presence of base:

C<sub>6</sub>H<sub>5</sub>CHCl<sub>2</sub> + H<sub>2</sub>O → C<sub>6</sub>H<sub>5</sub>CHO + 2&nbsp;HCl

References