A
1-l. three-necked flask is fitted with a
dropping funnel, a
stirrer, a
thermometer for reading low temperatures (Note
1), and a
condenser, to the upper end of which is attached a tube for disposing of the
hydrogen chloride evolved (Note
2). A mixture of
200 cc. of carbon disulfide and 180 g. (1.35 moles) of anhydrous aluminum chloride is placed in the flask which is then immersed in an ice-salt freezing mixture and stirred very vigorously until the temperature of the mixture is −5° or below. A mixture of
175 g. (1.3 moles) of p-cymene and
110 g. (100 cc., 1.4 moles) of acetyl chloride is added from the dropping funnel at such a rate that the temperature never rises above 5°. This addition requires about three and one-third hours (Note
3). The mixture is allowed to stand overnight and is then poured upon 1 kg. of cracked ice to which
200 cc. of concentrated hydrochloric acid has been added. The mixture is extracted with three
700-cc. portions of ether; the
ether solution is dried over anhydrous
calcium chloride and distilled at ordinary pressure from a
Claisen flask provided with an indented column, until the temperature reaches 190°. The material that remains in the flask is fractionally distilled twice under diminished pressure. The principal fraction is
aceto-p-cymene, a pale yellow oil boiling at
124–125°/12 mm. (
155–157°/30 mm.). It weighs
115–125 g. (
50–55 per cent of the theoretical amount) (Note
4). About
50 g. of cymene is recovered (Note
5), and there is a small amount (10–12 g.) of residual oil left in the flask (Note
6).