A 5-qt. enamel pail or bain-marie jar is fitted with two mechanical stirrers (Note 1) placed off center, a thermometer for reading low temperatures, and a dropping funnel, the lower end of which is placed just over the vortex created by one of the stirrer blades, so that each drop of added liquid is immediately mixed with and diluted by the chilled reaction mixture.

In the pail are placed 1 kg. (544 ml.) of concentrated sulfuric acid and 300 ml. of glacial acetic acid (Note 2), and this mixture is chilled by Dry Ice until the temperature is 0° to −5°. Next, 500 g. (585 ml.) of p-cymene (Note 3) is added from the dropping funnel with vigorous stirring, any rise of temperature being prevented by the addition of Dry Ice (Note 4). Concurrently the nitrating mixture is prepared from 369 g. (262 ml.) of nitric acid (sp. gr. 1.42) and 1 kg. (544 ml.) of concentrated sulfuric acid, and cooled to 0–5° by the direct addition of small pieces of Dry Ice (Note 4).

The hydrocarbon emulsion is then cooled to −15° to −10° and the nitrating mixture is admitted dropwise from the dropping funnel over a period of about 2 hours, avoiding any temperature rise (Note 4) and (Note 5). Stirring is continued for 10 minutes, after which the entire contents of the pail are poured, with adequate stirring, into a mixture of 1 kg. of cracked ice and 1 l. of water. Separation into layers occurs after about 2 hours, whereupon the lower acid layer is drawn off by siphoning or by means of a large separatory funnel (Note 6) and extracted twice, using 50-ml. portions of petroleum ether or 500-ml. portions of ether (Note 7). The extracts and crude nitrocymene are combined and washed three times with 300-ml. portions of water (Note 8), and the ether layer is dried by 50 g. of calcium chloride. After the ether is filtered and distilled, the residual liquid is fractionated under reduced pressure, using a 1-l. modified Claisen flask with indented neck. Fractions are collected at 15–17 mm. as follows: up to 125°, 25–30 g. (Note 9); 125–139°, 520–550 g. (78–82%), n_D26 1.5280; tarry residue, 25–30 g. The product is mainly 2-nitro-p-cymene but contains about 8% of p-nitrotoluene; it is suitable for reduction¹ to 2-amino-p-cymene, from which the p-toluidine is readily removed. Upon refractionation of the mixed nitro compounds, the last half is essentially pure 2-nitro-p-cymene, b.p. 137–139°/17 mm.; 128–131°/12 mm.; 108°/3 mm., n_D25 1.5290. The properties of pure 2-nitro-p-cymene are as follows: b.p. 126°/10 mm.; 142°/20 mm.; n_D20 1.5287.