Chlorine reacts with benzaldehyde to give

The flask is filled with the precise amounts of cold, dry benzaldehyde and is saturated with dry chlorine current. The evolution of hydrogen chloride occurs as a result of the chlorine gas's easy absorption. When the reaction has slowed down, mild boiling is used to maintain the external heat. Until no more hydrogen chloride is evolved, the chlorine stream is maintained. The excess chlorine is subsequently removed from the system using a stream of dry air or carbon dioxide. By distillation, benzoyl chloride is produced as an odourless fuming liquid with little colour. almost quantitative yield