Benzal Chloride

Benzal chloride is mainly produced for making benzaldehyde. It is a clear oily liquid that is sensitive to water. It is made by the chlorination of toluene under UV light.

Reaction:

C6H5CH3 + 2Cl2 ----> C6H5CHCl2 + 2HCl

Materials	Equipment
Dry Toluene	100ml graduated cylinder with stopper that will completely seal it
Chlorine Gas	Tubing (both glass and rubber)
Calcium chloride	Calcium Chloride tubes
	500 Watt Halogen lamp

Synthesis

Into a 100ml graduated cylinder, pour 70mls of dry toluene. Insert a 2-hole stopper into the cylinder. Stick a peice of glass tube through the rubber stopper and push it in until it touches the bottom of the cylinder then pull it up about 1cm. Make sure there is at least an inch sticking out of the top of the stopper for the tubing to be connected to. In the other hole, place a 3inch long peice and have 5mm of it stick out of the bottom of the stopper into the cylinder (but not touching the toluene). Set up the chlorine gas generator and connect it to a calcium chloride tube. You can connect it to another to be safe. Read Gas Drying for more information on this. Have a hose connect from the last calcium chloride tube to the tube that extends to the bottom in the graduated cylinder. Have another tube come from the other glass tube on the cylinder and direct it out a window or into a chain of neutralizing flasks. Place the graduated cylinder, with toluene and all connections, on a scale and weigh it. Record the weight. Set up the 500watt halogen lamp pointing at the cylinder about 1ft away from it and turn it on. Start generating the chlorine gas. Periodically weigh the graduated cylinder and stop chlorination when it has increased by 45grams. Also, the liquid inside should be up to 85ml on the graduated cylinder. If its not, its fine as long as its 45 grams heavier than before.

To purify: Pour the liquid into a 250ml boiling flask and set it up for simple distilation. Discard the first fraction until 5mls has been collected at above 198C. Then collect the fraction until there is about 5mls left in the boiling flask. This is your pure benzal chloride.