PREPARATION LXVI.

DIETHYL MALONATE, C,H12O4=CH2CO,CH.

LITERATURE.-Conrad (1880), Ann. Ch. Pharm. 204, 126; Venable (1880), Ber. 13, 1651; Claisen, Crismer (1883), Ann. Ch. Pharm. 218, 131.

One hundred grms. monochloracetic acid are dissolved in 200 grms. water in a porcelain basin, and the solution neutralised with 75 grms. potassium. carbonate. Seventy-five grms. powdered potassium cyanide are now added, and the mixture heated on the sand-bath until the reaction sets in with strong ebullition. When the reaction is over, the contents of the basin are evaporated as rapidly as possible on the sand-bath, with constant stirring, until a thermometer inserted into the brown semi-fluid mass indicates a temperature of 135°. The mass is allowed to cool without interrupting the stirring and, when cold, the hard saline deposit, consisting of potassium

chloride and potassium cyanacetate is finely powdered and introduced into a round-bottomed flask connected with a condenser. Two-thirds the weight of absolute alcohol is added and the mixture, heated on the water-bath, is saturated with dry hydrochloric acid gas.* The gas is conducted in through a funnel or wide adapter to prevent the inlet tube becoming choked with the crystalline precipitate which is formed. When hydrochloric acid has been passed in for about ten hours, the contents of the flask are cooled, poured into ice water and shaken with 300 c.c. commercial ether, in which the ethyl malonate dissolves. The ethereal layer is then separated from the acid liquid and washed with water and potassium carbonate solution, drawn off, dehydrated over calcium chloride and distilled. When the ether has been driven off, the greater portion of the residue distils at 190—200°. After one or two fractionations the ether is found to boil at 195-196° and is pure.

=

CH,C1.CO,H + KCN CH,CN.CO,H + KC1

Monochloracetic Acid

CN

Cyanacetic Acid.

CH2COOH + 2C2H¿OH + HCl =

Properties.-Colourless liquid; b. p. 195°; sp. gr.

1068 at 18°; insoluble in water.

PREPARATION LXVII.

/CO,H

ETHYLMALONIC ACID, CH2O4= C2H,CH CO2H

LITERATURE.—Wislicenus, Urech (1873), Ann. Ch. Pharm. 165, 93; Tupolew (1874), Ann. Ch. Pharm. 171, 243; Markownikow, Ann. Ch. Pharm. 182, 329; Conrad (1880), Ann. Ch. Pharm. 204, 134.

Sodium ethylate is first prepared by dissolving 2.3 grms. sodium in 25 grms. absolute alcohol, and the reaction completed, if necessary, on the water-bath as described on p. 132. Whilst the product is still slightly warm, 16 grms. malonic ether are added from a tap funnel. The liquid remains clear at first, but before the ether has all been added a white crystalline body (sodium ethyl malonate) separates out, and soon the whole solidifies. To the solid mass 20 grms. ethyl iodide are slowly added. The mass softens, and after continued shaking completely liquefies with evolution of heat. The product is now heated on the waterbath, when it becomes turbid from the separation of sodium iodide in the form of a fine powder.

After hours the liquid ceases to be alkaline, and the reaction is complete. The alcohol is distilled off on a brine-bath. On the addition of water an almost colourless oil separates out. The oil is sepa

rated by extraction with ether dehydrated over calcium chloride and distilled. When the ether has been driven off, almost the whole of the residue (ethyl diethyl-malonate) passes over at 206-208°.

Properties. Colourless liquid, with an agreeable fruity smell; b. p. 207°, sp. gr. 1'008 at 18°.

To obtain the free acid, the ether is saponified with caustic potash. To 25 grms. caustic potash in strong aqueous solution the ether is slowly added from a tap funnel. At first an emulsion forms, which soon solidifies to a white mass. This is heated on the water-bath with constant shaking for about three quarters of an hour, until it becomes completely liquid. The saponification is then complete. The product is diluted with water, neutralised with hydrochloric acid, and the free acid precipitated with calcium chloride as the calcium salt. This is separated from the solution by filtration and concentrated hydrochloric acid added. From the acid solution the free ethylmalonic acid is extracted by shaking with ether. After evaporating off the ether, the acid remains. behind as a syrup, which solidifies when cold. This is redissolved in water, boiled with a little animal charcoal to free it from any adhering colouring matter,

filtered and evaporated to syrupy consistency on the water-bath. The colourless acid crystallises on cooling.

NaI

Ethyl Diethyl Malonate.

C2H¿CH(CO2C2H5)2+ 2KOH C2H CH(CO2K)2+2C2H¿OH

Potassium Ethyl Malonate.

Properties.-Rhombic prisms; m. p. 111.5°, easily soluble in water, alcohol and ether; decomposes completely at 160° into carbon dioxide and butyric

acid.

PREPARATION LXVIII.

TRICHLORACETIC ACID, C2HCO2 = CCl2CO2H.

LITERATURE.-Dumas (1838), Compt. rend. 8, 609; Kolbe (1844), Ann. Ch. Pharm. 49, 341 and (1845) Ann. Ch. Pharm. 54, 183; Judson (1870), Chem. Soc. J. 24, 232; Clermont (1871), Compt. rend. 73, 113; (1872) 74, 1492; (1874) 76, 774.

The

In a flask of 500 c.c. capacity, 35 grms. commercial chloral-hydrate are heated to melting, and 100 grms. fuming nitric acid are added to the melted mass. mixture is heated carefully over a small flame until the reaction sets in. After a few minutes red fumes