PREPARATION XLI. TRIPHENYLMETHANE, C19H16=CH (C ̧H¿)1⁄2 LITERATURE.-Kekulé, Franchimont (1872), Ber. 5, 907; Hemilian (1874), Ber. 7, 1204; Friedel, Crafts (1877), Compt. rend. 1450; E. and O. Fischer (1878), Ann. Ch. Pharm. 194, 252; Schwarz (1881), Ber. 14, 1516; Friedel, Crafts (1882), Bull. Soc. Chim. 37, 6. Thirty-three grms. chloroform and 170 grms. benzene, both carefully dehydrated, are mixed together in a retort connected with a reflux condenser. Fifty grms. of aluminium chloride are added in portions of about 10 grms. at a time. On the addition of the chloride the reaction sets in spontaneously and the liquid begins to boil with copious evolution of hydrochloric acid. The aluminium chloride gradually dissolves, forming a dark brown oily liquid. When the aluminium chloride has been added, the mass is allowed to stand about twelve hours, and the reaction completed by heating for two hours on the sand-bath, when a further quantity of hydrochloric acid is evolved. The contents of the retort are cooled and poured into an equal volume of cold water, which decomposes the aluminium triphenylmethane compound with evolution of heat and the free hydrocarbon dissolves in the excess of benzene with a reddish brown colour. The upper layer of benzene is separated from the aqueous portion, and the former dehydrated over calcium chloride. The excess of benzene is now distilled off on the water-bath, and the dark-coloured residual liquid fractionated up to 200° at the ordinary pressure, and finally in vacuo. This FIG. 19. operation is conducted in the apparatus shown in Fig. 19, and consists of a retort and receiver, the latter being in connection with a water-jet aspirator. At first an oily liquid distils. This is impure diphenylmethane. When most of the diphenyl compound has passed over the distillation suddenly slackens. The receiver is now changed, and the contents of the retort more strongly heated. orange-coloured oil passes over, which crystallises in the receiver. The distillation is continued until the An distillate no longer solidifies on cooling. A black resinous mass remains in the retort. The crude triphenylmethane in the receiver is recrystallised from hot benzene, forming a crystalline molecular compound with the solvent of the formula C19H16 CH6, which separates out on cooling as a yellow crystalline mass. This is again crystallised from benzene, By heating the substance on the water-bath it loses benzene and the triphenylmethane which remains is finally crystallised from hot alcohol. CHC1, +2C6H6 = CH(CH)3 + 3HCl Properties.-Brilliant colourless plates; m. p. 92° i b. p. 360°; readily soluble in hot alcohol, in ether, and chloroform; with difficulty in cold alcohol. On dissolving in cold, fuming nitric acid, pouring into water and treating the precipitate with zinc dust and glacial acetic acid, leucaniline is formed. This is precipitated with ammonia, and on gently warming the dry precipitate with a few drops of hydrochloric acid on a piece of platinum foil the magenta coloration is obtained from the formation of rosaniline hydrochloride. PREPARATION XLII. ETHYL BENZOATE, C,H10O2 = C2H,CO.OC2H, 5 (Benzoic Ether.) LITERATURE.-Carius (1859), Ann. Ch. Pharm. 110, 210. Fifty grms. absolute alcohol and 25 ms. benzoic acid are mixed together in a flask of about 250 c.c. capacity fitted with a double-bored cork. Through one hole a small upright condenser is inserted, through the other a delivery tube passes, which dips below the liquid in the flask. Through the delivery tube a rapid current of hydrochloric acid gas is conducted into the mixture of alcohol and benzoic acid.* The gas is most conveniently generated by dropping conc. sulphuric acid from a tap funnel into a flask half-filled with conc. hydrochloric acid. The temperature of the mixture, as the gas passed in, rises to the boiling point of the alcohol, and the benzoic acid quickly dissolves. When the first reaction is over and the contents of the flask begin to cool again, the vessel is placed on the water-bath and the current of gas continued until fumes of the acid escape from the upper end of the condenser. The contents of the flask are now poured into water, when a colourless oil falls to the bottom. The oil is shaken with dilute sodium carbonate solution to dissolve unattacked benzoic acid, then with water, separated as carefully as possible from the latter and dehydrated over ignited potassium carbonate. It is decanted and distilled. The product boils nearly constantly at 211°. C6H5COOH + С2H5OH = C6H5CO2C2H5 + H2O. Benzoic Acid Properties.-Colourless, oily liquid, with a pleasant fruity smell; b. p. 2112°; sp. gr. 10502. Treated with conc. ammonia it yields benzamide and alcohol; boiled with caustic potash it splits up into its original constituents, benzoic acid (potassium salt) and alcohol (hydrolysis or saponification), |