In a
1-l. three-necked round-bottomed flask, fitted with an
efficient stirrer, a
reflux condenser, an inlet tube, and a
thermometer (Note
1) and (Note
2), are placed
102 g. (118 ml., 0.85 mole) of mesitylene,
147 g. (1.25 moles) of zinc cyanide (Note
3), and
400 ml. of tetrachloroethane (Note
4). The inlet tube is connected to a source of
hydrogen chloride (Note
5), and the mixture is stirred at room temperature while a rapid stream of dry
hydrogen chloride is passed through it. This is continued until the
zinc cyanide is decomposed; usually about 3 hours is required. The flask is then immersed in an
ice bath, the inlet tube is removed, and
293 g. (2.2 moles) of finely ground anhydrous aluminum chloride is added to the mixture (Note
6) and (Note
7), with
very vigorous stirring. The ice bath is then removed, and the passage of
hydrogen chloride is resumed for the remainder of the reaction period. The heat of reaction is sufficient to warm the mixture slowly, and a temperature of about 70° is reached at the end of an hour. A temperature of 67–72° is maintained for an additional 2.5 hours. The cooled mixture is decomposed by pouring it cautiously, with stirring by hand, into a
4-l. container about half full of crushed ice, to which has been added
100 ml. of concentrated hydrochloric acid. After the mixture has stood overnight, it is transferred to a
3-l. round-bottomed flask and refluxed for 3 hours. The organic layer is then separated, and the aqueous layer is extracted once with
50 ml. of tetrachloroethane. The combined
tetrachloroethane solutions are washed with
150 ml. of a 10% solution of sodium carbonate and distilled with steam. The first 800–900 ml. of distillate is set aside for recovery of the solvent (Note
8) and (Note
9), and the second portion is collected as long as oily drops are observed (Note
10). This distillate is extracted with
500 ml. of benzene, the solvent is removed on the
steam bath, and the residue is distilled from a
250-ml. modified Claisen flask. After a small fore-run, the
mesitaldehyde distils at
118–121°/16 mm. The yield is
95–102 g. (
75–81%) (Note
11) and (Note
12).