THE FORMATION OF PHLOROGLUCINOL. 165

XIX.-The li’ormation o f Phloroglucilzol by the Inter- action o f E t h y l Maloizate with its Sodium Derivutzve.

By CHARLES WATSON MOORE.

IN the year 1885, Baeyer made the important discovery that when ethyl malonate is heated with its sodium derivative a t 145O, condensation takes place and a derivative of phloroglucinol is formed which melts a t 104O, and which Baeyer considered was ethyl phloro- glucinoltricarboxylate, C,(OH),(CO,Et), (Bell., 1885, 18, 345’7).

During the course of an investigation involving the use of ethyl malonate, the author was led to reinvestigate this matter, and has been able t o prove that the substance formed under the conditions employed

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166 MOORE: THE FORMATION OF PHLOROGLUCINOL BY THE

by Baeyer is ethyl phloroglucinoldicarboxylate, C,H(OH),(CO,Et),, and not the above-mentioned tricarboxylate.

Since the difference in percentage composition between these two esters is small (a fact which accounts for the mistakes which have arisen as t o i ts composition), the molecular weight was determined in benzene solution by the cryoscopic method, and two determinations gave 270 and 273, whereas the molecular weights of the dicarboxylic and tricarboxylic esters are 270 and 342 respectively.

The determination of the ethoxyl groups, which was kindly carried out by Dr. W. H. Perkin, sen., in his new modification of Zeisel's apparatus (Trans., 1903, 83, 1367), also gave numbers which clearly show that the substance is a dicarboxylic ester.

When treated with bromine, it yields a bromo-compound having the com position C,Br(OH),( CO,Et),, which was first prepared by Oscar Bally (Bey . , 1888, 21, 1770), the process being a simple case of sub- stitution of hydrogen by bromine, whereas Bally, who supposed that the original ester was the tricarboxylic ester, was forced to assume that, during bromination, elimination of ethyl bromide and carbon dioxide had taken place, in order to account for the composition of the bromo-compound. If then the product of the condensation of ethyl malonate with its sodium compound is the dicarboxylic ester, i t follows that during the condensation, elimination of ethyl alcohol and carbon dioxide must have taken place, and, in proof of this, the author finds tha t the mixture invariably contains considerable quantities of sodium carbonate.

Since ethyl phloroglucinoldicarboxylate readily yields a triacetyl compound when heated with acetic anhydride, there can scarcely be a doubt that its constit:ition is represented by the formula :

C0,Et

OHAOH H\)CO,Et

O H

Ethyl Pldorog lzccino Zdicarboxylate, C,H( OH),( C0,Xt) ,. During this investigation, the above ester was repeatedly prepared

according to the directions given by Baeyer (Zoc. ci t . ) , but the purifi- cation was found to be tedious, for the compound, as Baeyer states, is yellow, and the alcoholic solution must be boiled for a long time with animal charcoal before the yellow colour can be removed. The pure ester, after repeated crystallisation, melted at 107" (Baeyer gives 104O), and was analysed with the following result :

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INTERACTION OF ETHYL MALONATE 167

0.2014 gave 0.3944 CO, and 0,0948 H,O. C = 53.6 ; H = 5.2. C,H(OH),(CO,Et), requires C = 53.3 ; H = 5.2 per cent.. C,(OH ) ,(CO,Et), ?, C = 5 2 . 6 ; H=5*2 ?,

The analytical numbers given by Baeyer are C = 52.4 ; H = 5.2 per cent. As the difference in the percentage composition of the di- and tri-carboxylic esters is so small, the molecular weight was determined by the cryoscopic method, using benzene as the solvent. Two experi- ments gave the values 270 and 273, whereas the molecular weight of the dibasic ester, C,,H,,07, is 270, and that of the tribasic ester, C,,H,,O,, is 342.

The view that the ester is ethyl phloroglucinoldicarboxylate received further confirmation from the determination of the ethoxyl groups by Dr. W. H. Perkin."

0.3436 gave 0.5641 A.gI, corresponding with OEt = 31.5.

The dibasic ester, C,,H,,07, contains OEt = 33.3 per cent. The tribasic ester, C,,H,,O,, ,, C)Et=39*4 ,,

0.3504 ,, 0.5807 AgI, 9 ? ,, )) =31.8.

Ethyl Triacet y Zpliloroglucinolcliarbox~~c~te, C,H ( C,H,O,) 3( CO,E t),.

This substance, which has already been described by Oscar Bally (Ber , 1888, 21, 1768), was prepared by his method. After repeated recrystallisation from alcohol, it was obtained as a colourless, crystal- line mass which melted at 96' (the m. p. 75-76' given by Bally is evidently a clerical error).

0.1488 gave 0,2970 CO, and 0.0690 H,O.

Bally found C = 5 3 * 9 and H=5.0, a result which agrees fairly well with the above, but he assumed that his substance was the triacetyl compound of ethyl phloroglucinoltricarboxylate.

C = 54-4 ; H = 5.1. C,,H,,O1, requires C = 54.5 ; H = 5.0 per cent.

EtlqE Bromoph Eorog Zzccin oldicar box2 late, CbBr (OH) 3( C0,E t ) 2.

This substance was first obtained by Bally (Zoc. c i t . ) by treating the ester prepared by Baeyer's process with bromine in chloroform solution, I n this preparation also, Bally's directions were carefully followed and the bromo-compound was obtained, exactly as he describes, in colourless needles melting at 128'. The results obtained on analysis were : C = 40.9 ; H -- 3.7 ; Br = 22.8.

C,,H130,Br requires C = 41.2 ; H = 3.7 ; Br = 22.8 per cent.

* The determination of ethoxyl groups always gives figures rather lower than the theoretical, the loss being apparently due to the conversion of a small amount of the ethyl iodide into ethylene during the process

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168 THE FORNATION OF PHLOROGZUCINOL.

The analytical results obtained by Bally agree fairly well with those just given, and it is curious tha t he should assume, in order t o explain the composition of this bromo-compound, that, during the bromina- tion, carbon dioxide and ethyl bromide are eliminated, thus convert- ing ethyl phloroglucinoltricarboxylate into ethyl bromophloroglucinol- dicarboxylate, whereas there is no indication of any such elimination of carbon dioxide.

That carbon dioxide is formed during the condensation of ethyI malonate with its sodium compound by the process recommended by Baeyer was proved by carrying out the operation in a flask fitted with a dropping funnel, and through which hydrogen was passing during the whole operation. On adding hydrochloric acid through the dropping funnel to the product and lending the gases through baryta water, it was a t once seen tha t quantities of carbon dioxide were being evolved.

Prepamtion of Ethyl Pl~ZorogZucinoldicccr6ox~Zat~ by Heating Ethyl Sodionzcdo.lc;ate with Ethyl McLZonute in AZcohoZic Ayolutioiz.

This method, which gives a pure product much more readily than that described by Baeyer, was carried out as follows.

Sodium (14.4 grams) is dissolved in alcohol (200 grams) and, when nearly cold, mixed with 200 grams of ethyl malonate. The mixture, while still warm, is transferred to soda-water bottles and heated in a boiling brine bath a t 105-108° for 15 hours. The white precipitate, which separates during this operation, consists of the sodium compound of ethyl phloroglucinoldicarboxylate mixed with sodium carbonate ; it is collected at the pump, mashed with alcohol, and then dissolved in water acidified with hydrochloric acid, when carbon dioxide is evolved and the ester precipitated as an almost colourless crystalline mass. After one crystallisation from alcohol, the ester was perfectly colourless and melted a t 106-107°.

0.1736 gave 0.3393 CO, and 0,0815 H,O. C6H(OH),(C0,Et), requires C = 53.3 ; H = 5.2 per cent.

This ester yields phloroglucinol on hydrolysis, and i ts identity with the ester prepared by Baeyer’s process was proved by mixing equal quantities of the two specimens when there was no alteration in the melting point.

The yield obtained in alcoholic solution is practically the same as tha t obtained by .Raeyer’s process, but a large amount of ethyl malonate may be recovered and used in a subsequent operation.

C = 53.3 ; H = 5.2.

THE OWENS COLLEGE, __ -. -__

BIIANCIIEGTEH.

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