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).

A 1-l. three-necked flask with ground-glass joints is fitted with a mercury-sealed stirrer (Note 1) and (Note 2), a glass tube of 6-mm. internal diameter which runs to the bottom of the flask, and a Friedrich condenser, protected by a drying tube. A solution of 90 g. (0.49 mole) of mesitoyl chloride (p. 555) in 270 g. of carefully dried xylene is placed in the flask together with 20 g. of palladium-barium sulfate (Note 3). The contents of the flask are refluxed while a stream of hydrogen (Note 4), which has been freed from oxygen by passage through Fieser's solution,⁴ and dried by passage through concentrated sulfuric acid followed by a drying tube of Drierite (Note 5), is bubbled through the suspension until hydrogen chloride ceases to be evolved (Note 2). The catalyst is then removed by filtration and the xylene distilled. The residual liquid is transferred to a 125-ml. modified Claisen flask and distilled. The product boils at 96–98°/6 mm., and weighs 53–60 g. (70–80%) (Note 6).