Preparation of 4-nitrobenzal chloride
The chlorination is best carried out in a three-necked flask with a mercury immersion lamp, a gas inlet tube, and a highly efficient reflux condenser.
If no mercury immersion lamp is available, the mixture can be irradiated from outside with a 500-watt photolamp or the chlorination can be carried out in direct sunlight. However, the reaction then takes place somewhat more slowly and the yields are generally lower. The gaseous chlorine is dried in a wash-bottle with concentrated sulfuric acid. An empty wash-bottle must be connected on either side of this washing bottle as safety vessels. The 4-nitrotoluene is heated to the boiling point, using a heating bath, and a vigorous stream of gaseous chlorine is passed in. During the chlorination reaction no gaseous chlorine should pass through the condenser (color). Chlorination is continued until the calculated increase in weight has been obtained. On cooling, the solidified 4-nitrobenzal chloride can be purified directly by filtering off with suction and recrystallization from (ethanol/hexane). The yield is 80%, m.p. 46 °C (ethanol/hexane).
Organicum. Practical Handbook of Organic Chemistry, by Heinz Becker, Werner Berger and Günter Domschke, Addison-Wesley Pub. Co, 168-169, (1973)