The action of thionyl chloride and of phosphorus pentachloride on the methylene ethers of catechol derivatives / by George Barger.

  • George Barger
Date:
[1908]
Catalogue details

Licence: Attribution 4.0 International (CC BY 4.0)

Credit: The action of thionyl chloride and of phosphorus pentachloride on the methylene ethers of catechol derivatives / by George Barger. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    agrees in every respect with that of an aromatic acid chloride, and leaves no doubt as to its constitution. It has been employed in the synthesis of new catechol derivatives, a number of which are described below. In accordance with what has been said above, the carbonate of protocatechuoyl chloride should be produced directly from piper- onylic acid by the action of thionyl chloride at 180°, and this was indeed found to be the case. On removal of the excess of thionyl chloride in a vacuum, the acid chloride remains behind as a crystalline mass, and it was in this experiment that its true nature was first recognised. The direct production of cyclic carbonates by successive treatment of methylene ethers with phosphorus pentachloride and with cold water has already been observed by Delange (Gompt. rend., 1904, 138, 423 and 1701) who obtained in this way the cyclic carbonates of 3 :4-dihydroxy-l-ethyl-, -a-l-propyl-, and -1-isopropyl-benzene. It seems safe to conclude from the above evidence that the two chlorine atoms which are introduced by phosphorus pentachloride into the methylene group are much more labile than any other chlorine atoms which may be introduced at the same time into another part of the molecule. By cold water, moist air, anhydrous formic acid, glacial acetic acid, or acetic anhydride (Delange) they are replaced by an oxygen atom; thionyl chloride introduces this oxygen atom at the outset. The violence with which these two chlorine atoms react with hydroxyl- and amino-groups is without parallel among aromatic chloro-compounds, although not surprising if we regard the substances in question as the dichlorides of an ethereal salt of orthoformic acid. If we consider that benzylidene chloride requires heating with water to 140—160° in order to con- vert it into benzaldehyde, we should not expect the carbonate of dihydroxybenzylidene chloride to react with cold water. The two chlorine atoms, which Pauly replaced by an oxygen atom in the production of protocatechualdehyde carbonate, are therefore those of the aldehyde group and not, as he seems to imagine, those in the carbonyl (methylene) group. Experimental. Conversion of Methylenedioxybenzene into Carbonyldioxybenzene. 1-45 Grams of crude methylenedioxybenzene, b. p. 170 — 180°, con- taining a little methylene iodide, and obtained by the action of methylene iodide on disodium catechol (Moureu, Bull. Soc. cliim., 1896, [iii], 15, 655) were heated for half an hour under a reflux condenser with 3-5 grams (2 mols.) of phosphorus pentachloride,