The apparatus consists of a
1-l. three-necked flask equipped with a
mechanical stirrer, a
250-ml. dropping funnel, and a
Friedrichs reflux condenser fitted with a
calcium chloride drying tube.
Magnesium turnings (13.4 g., 0.55 g. atom) and
200 ml. of anhydrous diethyl ether are put in the flask (Note
1). Slow stirring is started, and
4 ml. of bromobenzene (Note
2) is added from the funnel. After reaction has started (Note
3), the stirring rate is increased, and moderate reflux is maintained by addition of
80.5 g. of bromobenzene (making a total of 86 g. or 0.55 mole) in
100 ml. of ether. The solution is refluxed for 30–45 minutes after the addition and is cooled to room temperature. Stirring is continued while a solution of
51.5 g. (0.50 mole) of benzonitrile (Note
2) in
100 ml. of ether is added slowly enough (Note
4) to maintain only a gentle reflux. On completion of the addition, the reaction, mixture of pale-yellow liquid and white solid is refluxed with stirring for 4–6 hours. The stirred mixture is cooled to room temperature, and the Grignard-nitrile complex is decomposed by cautious addition of
120 ml. (3 moles) of anhydrous methanol (Note
5).
On completion of the
methanol addition, the mixture is stirred for 30 minutes and filtered. Low-boiling material is stripped from the filtrate, and the residue is distilled through a
45-cm. Vigreux column at reduced pressure. There is a fore-run, b.p.
120–127° (3.5 mm.), that weighs about
5 g. Then
55–73 g. (
61–81%) of
diphenyl ketimine is collected at
127–128° (3.5 mm.) or
151–152° (8 mm.);
n20D 1.6180–1.6191 (Note
6). The product should be stored under
nitrogen to prevent yellowing.