80--200° about 15 grams. 200-240 = 128–133 grams. Residue = about 10 grams.

The thermometer rises rapidly to 200°, only small quantities of alcohol, ether, and a little unchanged trimethylene bromide passing over below this temperature, a proof that practically the whole of the ethyl acetoacetate had been converted into ethyl methyldehydrohexonecarboxylate.

The fraction 200-240° is an almost colourless oil, which consists, in spite of the wide range of temperature, of nearly pure ethyl methyldehydrohexonecarboxylate, the yield of which is generally 83 to 86 per cent. of the theoretical, and in some cases, with very careful working, as much as 90 per cent. has been obtained. Its formation by this new method is represented by the equations—

(1.) CHş·CO-CHNa-COOC,H. + C,HBr =

The high boiling residue left in the retort is probably the product of the action of 2 mols. of ethyl acetoacetate on 1 mol. of trimethylene bromide. It is at present under investigation.

Acetobutyl Bromide, CH, CO-CH2 CH2 CH2 CH2Br.

In preparing acetobutyl bromide, the fractionated ethylic methyldehydrohexonecarboxylate is dissolved in about three times its volume of a saturated solution of hydrogen bromide (sp. gr. about 1·7), and the mixture allowed to stand for 24 hours. The whole is then poured into a large volume of cold water and the precipitated oil separated. The solution still contains a considerable quantity of the bromide, which can be completely extracted with ether if the solution is first neutralised with soda. The separated oil and the ethereal solution are mixed together, washed with dilute sodium carbonate solution, dried over calcium chloride, and the ether distilled off.

The acetobutyl bromide is thus obtained as a brownish oil, the yield of the crude product being about 86 per cent. of the theoretical. The crude bromide is now fractioned under diminished pressure, when the greater portion distils at a constant temperature (under 150 mm. at 155-160°; under 90 mm. at 135–137°), leaving as a residue a dark-brown oil, amounting to about 16 to 20 per cent. of the whole.

Ethyl aw-Diacetylcaproate.

When acetobutyl bromide is warmed with an alcoholic solution of ethyl sodacetoacetate, sodium bromide separates, and ethyl aw-diacetylcaproate is formed, thus:—

CH,CO-CHNaCOOC,H + CH, COCH,CH,CH,CH,Br

3

CHCOCH-COOC,H

CH,CH,CH,CH,COCH, + NaBr.

In preparing this substance, 80 grams of ethylic acetoacetate were dissolved in a solution of 14 grams of sodium in 150 grams of absolute alcohol, 110 grams of acetobutyl bromide added, and the whole heated on a water-bath in a flask connected with a reflux condenser. As soon as the mixture came to the boiling point, sodium bromide began to separate, and in a very short time the reaction was at an end. The alcohol was distilled off, the residue mixed with water, the product extracted twice with ether, the ethereal solution washed with water, dried over calcium chloride, and the ether evaporated.

The thick, oily residue, which weighed 144 grams, was readily purified by fractionation under reduced pressure.

The pure substance boiling at 238-242° (200 mm. pressure) gave the following result on analysis:

0.1435 gram substance gave 0.3333 gram CO2 and 0·1174 gram H2O.

Ethyl aw-diacetylcaproate is a thick, colourless oil, having a faint odour. It is almost insoluble in water, but readily miscible with ether and alcohol.

Hydrolysis of Ethyl aw-Diacetylcaproate.

The action of caustic potash on ethyl aw-diacetylcaproate may take place in one of the following three ways, according to the conditions of the experiment :

1st. When the etheral salt is mixed with an excess of a solution of strong potash in methyl alcohol and allowed to stand in the cold, aw-diacetylcaproic acid is formed, thus :

2ndly. When the ethereal salt is hydrolysed by boiling with dilute alcoholic potash, aw-diacetylpentane is formed, thus:

3rdly. When the hydrolysis takes place in the presence of a large excess of boiling alcoholic potash, besides aw-diacetylpentane, w-acetylcaproic acid is formed, thus:

CHCOCH-COOC,H,

+2KOH=CH, COOK + C2H2OH

CHCO [CH,] CH

+ CH ̧•CO·[CH2] COOK, Potassium w-acetylcaproate.

CH, CO CH-COOH

aw-Diacetylcaproic Acid, CH,CO [CH,]CH,

This acid is prepared by dissolving the crude ethereal salt in an excess of a cold saturated solution of pure potash in methyl alcohol, and allowing the mixture to stand for 24 hours. The resulting slightly brownish solution is placed over sulphuric acid in a vacuum until nearly all the alcohol has evaporated, the residue dissolved in water and repeatedly extracted with ether to remove traces of diacetylpentane which are invariably formed during the reaction. The alkaline solution is carefully acidified with dilute sulphuric acid, the clear liquid extracted several times with pure ether, the ethereal extract dried over calcium chloride and evaporated at a low temperature on a water-bath. The resulting slightly yellowish oil, after the removal of the last traces of ether, consists of nearly pure aw-diacetylcaproic acid, as the following analysis shows:

0-1769 gram substance gave 0·3886 gram CO2 and 0·1326 gram H2O.

Diacetylcaproic acid is miscible with water in all proportions, the solution reacting strongly acid; the addition of a drop of ferric chloride to this solution produces a slight brownish-violet coloration. If a small quantity of the acid is gently heated in a test-tube, car

bonic anhydride is evolved, and the resulting oil, on distillation, solidifies on the cooler portions of the tube to colourless plates consisting of pure aw-diacetylpentane :

The salts of diacetylcaproic acid are mostly readily soluble in water and difficult to prepare in a pure condition. The silver salt is a colourless, seemingly amorphous compound, readily soluble in cold water. In an aqueous solution of the ammonium salt, ferric chloride produces a light brown precipitate, which is quickly decomposed on heating; lead acetate gives no precipitate in dilute solutions, but copper sulphate produces a light green precipitate readily soluble in warm water. Mercuric nitrate gives a white precipitate which quickly dissolves when the solution is warmed.

CH2

aw-Diacetylpentane, CH, CO CH, CH, CH, CH, CO-CH,.

In the first attempts at preparing this diketone, ethyl aw-diacetylcaproate (1 mol.) was mixed in the cold with a dilute solution of potash (2 mols.) in methyl alcohol, and after standing for two days a further quantity of potash (4 mols.) was added, and the mixture boiled for six hours. After distilling off the alcohol, the residue was dissolved in water, the product extracted with ether, the ethereal solution dried over calcium chloride and evaporated. Aslightly yellowish oil was obtained containing, besides diacetylpentane, a second substance which is with difficulty separated by fractional distillation, It could be removed, however, by shaking with sodium hydrogen sulphite solution, collecting the solid double compound with diacetylpentane which is formed, washing this with ether, and decomposing with sodium carbonate. In this way a beautiful crystalline substance was obtained which gave the following numbers on analysis :0.1528 gram substance gave 0·3890 gram CO, and 0·1435 gram H2O.

As this process was very inconvenient for the preparation of large quantities of this substance, experiments were made with the object of improving the yield, and as a result the following method was found to give the largest quantity of pure diketone.

Rather more than the calculated quantity of potash required for hydrolysis (2 mols.) is dissolved in a little methyl alcohol, with the addition of a few drops of water; about one third of this solution is mixed with the ethyl diacetylcaproate and the mixture heated to boiling on the water-bath, in a flask connected with a reflux apparatus, for about five minutes, during which operation a quantity of potassic carbonate separates. Another third of the alcoholic potash is now added and the heating continued. In about 10 minutes the remainder of the potash is poured in, the alcohol at once distilled off and the residue mixed with water.

The product is extracted two or three times with ether, the extract dried over calcium chloride, and the ether evaporated. In this way an almost colourless residue is obtained which may readily be purified by fractionation under reduced pressure.

The approximate yield of the crude substance is 50-52 grams from 100 grams ethyl diacetylcaproate. This oil on fractioning behaves somewhat curiously. Thus, under a pressure of 300 mm. the thermometer rises rapidly to 170°, between which temperature and 190° about 5 per cent. distils, as a colourless oil which on cooling shows no signs of solidifying. The distillate between 190° and 219° solidifies entirely, and forms about 90 per cent. of the whole, and on several occasions it was noticed that although the substance gave good numbers on analysis it still possessed no constant boiling point. In order if possible to settle this point, the pure solid substance was refractioned under 240 mm. pressure without, however, any very definite boiling point being noticed. In fractioning large quantities, the nearest approach to a constant boiling point has been 212-215° (300 mm.), and 175-178° (130 mm.).

An analysis of the substance fractioned in this way gave the following numbers:—

01725 gram substance gave 0·4367 gram CO2 and 0·1617 gram

aw-Diacetylpentane, purified by washing with ether on a porous plate, melts at about 48-49°. It is readily soluble in cold ether, alcohol, acetone, chloroform, and warm light petroleum. Small particles thrown on to water move about rapidly with a rotatory motion, and gradually dissolve; but separate again on the addition of potassic carbonate. When shaken for some time with a saturated