of the pump, quickly washed with water, dried at 100°, and weighed. The amount of acid corresponding to it was then calculated, allowance being made in each case for the water of crystallisation in the salt, which is not expelled at a temperature below 120°. The calcium salt was finally decomposed by dissolving it in hot concentrated hydrochloric acid, and the acid which separated on cooling was carefully examined. In each case, it proved to be a substituted succinic acid. The results of these experiments may be tabulated as follows:

* N. B. –Figures in this column express the percentage yield of the succinic acid obtained in each case in terms of that theoretically possible from the amount of the acetoacetate originally taken in the experiment.

Second Series.-Ethylic acetosuccinate, and its B-methyl and Bẞ-dimethyl derivatives, contain a hydrogen atom in the a-position replaceable by alkyl groups. Their sodium compounds were accordingly treated with methylic iodide in alcoholic solution, and the methylated products isolated and fractionated under diminished pressure in a manner similar to that already described. After noting the yield, which in each case amounted to about 80 per cent. of the theoretical, the oil was hydrolysed with alcoholic potash, and the resulting succinic acids were finally obtained and estimated as calcium salts. The results of these experiments are tabulated on p. 849, the yields of succinic acids for purposes of comparison being stated in terms of the amounts theoretically obtainable from the quantity of ethylic acetoacetate originally employed for the preparation of the acetosuccinate (compare Table I).

B. Preparation of Substituted Succinic Acids from Ethylic Malonate: Separation of Isomeric Methyl-substituted Succinic and Glutaric Acids.

The object of these experiments was to determine the actual quantities of isomeric succinic and glutaric acids obtainable as the result of the interaction of ethylic sodiomalonate, or its methyl derivative, and ethylic a-bromopropionate, or a-bromisobutyrate, and subsequent hydrolysis of the resulting mixture of ethylic tricarboxylates with concentrated hydrochloric acid (see p. 842). The method employed in each case was identical with that given under section A, except in so far as ethylic malonate, or its methyl derivative, was used instead of ethylic acetoacetate. The product was isolated and fractionated under reduced pressure in much the same manner as there described (p. 847). The resulting mixture of ethylic tricarboxylates was hydrolysed by boiling it in a reflux apparatus on a sand-bath with excess of concentrated hydrochloric acid until the whole of the oil had disappeared. In some cases, part of the succinic acid separated on cooling; if so, it was at once removed by filtration at the pump, dried on porous plates, and then at 100°. The filtrate, or the original liquid, in cases where no acid separated, was made alkaline with strong ammonia, and the solution of ammonium salts boiled with excess of a 25 per cent. solution of calcium chloride, whereby the insoluble calcium salt of the succinic acid present was at once precipitated. This was collected by the aid of the pump, washed with water, dried at 100° and weighed. The quantity of acid corresponding to it was then calculated, allowance being made in each case for the water of crystallisation in the salt which is not expelled below 120°. The calcium salt was afterwards decomposed by dissolving it in hot concentrated hydrochloric acid, and the acid which separated out on cooling examined. In each case, it proved to be a succinic acid. To the filtrate from the insoluble calcium salt was added an excess of strong hydrochloric 3 L

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acid, it was then saturated with ammonium sulphate, thoroughly extracted with ether, and the ethereal solution dried over anhydrous sodium sulphate. After distilling off the ether, an acid oil, which crystallised on standing in a vacuum over sulphuric acid, always remained. The residue was in each case recrystallised from a mixture of benzene and light petroleum, and the recrystallised acid examined; it always proved to be a glutaric acid isomeric with the succinic acid obtained from the insoluble calcium salt.

The results of these experiments are given in Table III, which shows the yields of isomeric succinic and glutaric acids respectively obtained in each case, in terms of the amounts theoretically possible from the quantity of ethylic malonate or methylmalonate used.

One very curious feature in connection with these experiments is the fact that whilst ethylic a-bromisobutyrate reacts with ethylic sodiomalonate giving a mixture of ethylic tricarboxylates which on hydrolysis with concentrated hydrochloric acid yield a considerable quantity of as-dimethylsuccinic acid, no trimethylsuccinic acid can be obtained under similar conditions from the product of the interaction of ethylic a-bromisobutyrate and ethylic sodiomethylmalonate. We have many times tried the experiment, but always with the same result, and our experience is confirmed by that of other workers.

It is evident that the product of the interaction of ethylic sodiomalonate and ethylic a-bromisobutyrate must consist of a mixture of the ethylic tricarboxylates, (COOEt),CH•C(CH3)2 COOЕt and (COOEt),CH⚫CH2 CH(CH ̧)·COOEt, in which the first greatly predominates, for the ratio between the as-dimethylsuccinic and a-methylglutaric acids obtained on hydrolysing the product with strong hydrochloric acid is 2:1. Both these tricarboxylates contain a hydrogen atom in the a-position replaceable by alkyl radicles. The methylated product on hydrolysis should, therefore, give a considerable amount of trimethylsuccinic acid, and this proved to be the case. The following are the details of the experiment.

To the solution of 3.35 grams of sodium in 40 grams of ethylic alcohol were added 40 grams of the refractionated product of the interaction of ethylic sodiomalonate and a-bromisobutyrate (b. p. 155-163° under 18 mm. pressure); no solid sodium derivative separated out. 25 grams of methylic iodide were then very carefully added, for much heat was evolved. The liquid was heated for 11 hours on the water-bath until it became quite neutral. It was then poured into water, and the oil extracted with ether; the ethereal solution, after washing with a dilute solution of sodium thiosulphate, was dried over calcium chloride, and after distilling off the ether, residual oil was fractionated under 20 mm. pressure. A fraction amounting to 32 grams distilled over at 164-166°, the yield being 76 per cent. of that theoretically obtainable.

the

The whole was now hydrolysed by boiling it with excess of concentrated hydrochloric acid in a reflux apparatus for 5 hours. No acid separated out on cooling. The trimethylsuccinic and aa-dimethylglutaric acids were then separated by means of their calcium salts in a manner similar to that already described, and we finally obtained 11 grams of trimethylsuccinic acid (m. p. 145—147°) and 5·2 grams of a mixture of cis- and trans-aa-dimethylglutaric acids (m. p. 102-105°). The total yield of acid was 16.2 grams or 90 per cent. of that theoretically possible from the quantity of oil hydrolysed, and the ratio between the trimethylsuccinic and aa,-dimethylglutaric acids was 2: 1. From the results recorded in Table III, together with those of the experiment just described, it will be seen that 35 per cent. of the theoretical yield of trimethylsuccinic acid may be obtained from ethylic malonate.

C. Preparation of Trimethylsuccinic Acid from Ethylic a-Cyanopropionate.

It has already been stated that a mixture of trimethylsuccinic and aa-dimethylglutaric acids is obtained when the product of the inter

action of the sodium compound of ethylic a-cyanopropionate and ethylic a-bromisobutyrate is hydrolysed with concentrated hydrochloric acid (p. 845). Up to the present time, this has been the only method by which trimethylsuccinic acid has been prepared synthetically in any quantity. We have made a large number of experiments with this method, which is carried out in exactly the same way as that already given for the preparation of succinic acids from ethylic malonate (section B), except, of course, that the latter is replaced by a molecular proportion of ethylic a-cyanopropionate. The resulting mixture of ethylic trimethylcyanosuccinate and aa1-dimethylcyanoglutarate was hydrolysed by means of concentrated hydrochloric acid, and the trimethylsuccinic and aa,-dimethylglutaric acids separated by means of their calcium salts as described in the preceding section.

The ethylic a-cyanopropionate used in the first series of experiments was prepared by the action of potassium cyanide on an alcoholic solution of ethylic a-bromopropionate (Bone and Perkin, Trans., 1895, 67, 421), whilst in the second series, ethylic a-cyanopropionate prepared by the methylation of ethylic cyanacetate was employed. Our results may be tabulated as follows:

D. Preparation of Ethylic Methylcyanosuccinates from Ethylic Cyanacetate.

The sodium compound of ethylic cyanacetate readily reacts with ethylic a-bromopropionate or a-bromisobutyrate, yielding a substi tuted ethylic cyanosuccinate as already explained (p. 845). The ethylic B-monomethyl- and ßß-dimethyl-cyanosuccinates so produced each contain a replaceable hydrogen atom, and on methylation therefore yield ethylic aß-dimethyl- and trimethyl-cyanosuccinates respectively. It is thus possible to prepare any methyl-substituted ethylic cyanosuccinate from ethylic cyanacetate, and these reactions afford a new method for the preparation of the corresponding succinic acids.