LITERATURE.-Berthelot (1856), Ann. Ch. Phys. (3) 48, 304; Wurtz (1857), Ann. Ch. Phys. (3) 51, 91; Henry (1870), Compt. rend. 70, 638; Tollens (1870), Ann. Ch. Pharm. 156, 168. Seventy-five grms. bromine are slowly added in small portions at a time to 50 grms. allyl iodide contained in a flask, which is connected with an air condenser and well cooled in a freezing mixture.* The liquid is then allowed to stand twenty-four hours and separated by filtration from the iodine, which has meanwhile crystallised out. The brown filtrate is repeatedly washed with dilute caustic soda solution and then with water. The allyl bromide is separated from the aqueous portion, dehydrated over fused calcium chloride and distilled. The colour of the liquid on boiling changes to a dark brown and iodine vapours are given off abundantly. The distillate is again treated with caustic soda and water, &c., and redistilled. The temperature, indicated by the thermometer, rises rapidly to 180° and the greater portion of the liquid distils at 200-220°. This fraction crystallises on standing for a time in a freezing mixture and the crystals are separated from the mother liquor by decantation. The product is purified by repeated distillations. C3H5I + Brg = C3H5Br3 + I Properties.-Colourless glistening prisms; m. p. 16°, b. p. 219–220°. PREPARATION LXXV. TRICARBALLYLIC ACID, CH2O=CH.COOH. CH2.COOH. CH,.COOH. (Propenyl-tricarboxylic Acid.) Literature.—Simpson(1865), Proc. Roy. Soc. 14, 77. Fifty grms. allyl bromide are dissolved in excess of alcohol and 36 grms. coarsely powdered potassium cyanide added. The whole is then heated in a sodawater bottle with the cork well tied down for 15 hours in the water-bath. The bottle is well cooled and carefully opened and the alcoholic liquid filtered froni the potassium bromide, which has separated out. The filtrate is now heated with reflux condenser on the water bath with a sufficient quantity of caustic potash (40 grms.) to decompose the cyanide formed, until the evolution of ammonia gas has ceased. The alcohol is distilled off on the brine-bath and an excess of nitric acid added to the cooled residue. On evaporating the mass on the water-bath a residue consisting of potassium nitrate and free tricarballylic acid remain from which, after being well dried and powdered, the latter may be extracted with absolute alcohol. On evaporating off the alcohol, the acid remains as a darkcoloured substance and is purified by recrystallisation from water with the addition of animal charcoal. C3H5Br2+3KCN = C3H5(CN)3 + 3KBr Propenyl Tribromide Propenyl Tricyanide. C3H5(CN)3 + 3KOH + 3H2O = СH(COOK), + 3NH3 Potassium Tricycarballylate. Properties.-Colourless rhombic plates; m. p. 158°; casily soluble in water and alcohol. PREPARATION LXXVI. = GLYCERIC ACID, C2H2O, CH2(OH).CH(OH).CO2H (Dioxypropionic Acid.) LITERATURE.-Debus (1858), Ann. Ch. Pharm. 106, 79; Sokolow (1858), Ann. Ch. Pharm. 106, 95; Beilstein (1861), Ann. Ch. Pharm. 120, 226; Mulder (1876), Ber. 9, 1902. 50 grms. glycerin. 50 fuming nitric acid, sp. gr. 15. Fifty grms. glycerin diluted with an equal volume of water are introduced into a tall narrow glass cylinder. 50 grms. fuming nitric acid sp. gr. 1'5 are carefully run in below the surface of the glycerin by means of a funnel (the neck of which is drawn out into a fine tube) so that two layers are formed. The cylinder is left at the ordinary temperature for some little time until the two layers have diffused and formed a homogeneous liquid. The contents of several such cylinders are slowly evaporated on the water-bath to a syrupy consistence. The residue is diluted with about 2 litres of water and the aqueous solution of glyceric acid neutralised with lead carbonate and a small quantity of lead oxide. Towards the end of the operation the liquid is heated to boiling and filtered whilst hot. On concentrating and cooling the aqueous solution, the impure lead salt of glyceric acid is obtained, which may be purified by recrystallisation. The salt which crystallises out in crusts on the sides of the vessel to which it firmly adheres, may be detached by warming. By concentrating the mother liquors a further quantity of crystals slowly separates out. The finely powdered salt is mixed into a paste with water and decomposed in portions of 25 grms. with sulphuretted hydrogen. The aqueous solution, filtered from lead sulphide, is evaporated on the water-bath, when the acid remains. in the form of a thick syrup. C3H5(OH)3 + O2 = C3H6O4 + H2O Glycerin Glyceric Acid. Properties.-Strongly acid syrup of a faint yellow colour, which does not crystallise; soluble in water and alcohol, insoluble in ether. PREPARATION LXXVII. B-IODPROPIONIC ACID, С2H¿IO=CH2I.CH2COOH. LITERATURE.-Beilstein (1861), Ann. Ch. Pharm. 120, 230 and (1862) 122, 366; Moldenhauer (1864), Ann. Ch. Pharm. 131, 323; Kekulé (1864), Ann. Ch. Pharm. 131, 223; Mulder (1876), Ber. 9, 1902; Wislicenus (1873), Ann. Ch. Pharm. 166, 1; Erlenmeyer (1878), Ann. Ch. Pharm. 191, 284. 52 c.c. glyceric acid sp. gr. 1'26. 100 grms. phosphorus diiodide. One hundred grms. phosphorus diiodide 1 are added in small quantities to 52 c.c. glyceric acid sp. gr. 1*26 contained in a large round-bottomed flask and in order Preparation of Phosphorus Diiodide (Fittig (1886), Grundriss der Org. Chem.).-Forty-one parts dry powdered iodine are added to a well-cooled solution of 5 parts phosphorus dissolved in carbon bisulphide. The carbon bisulphide is then distilled off. |