GB651797A - Preparation of 4-vinylcyclohexene dioxide - Google Patents

Abstract

4-Vinyl cyclohexene dioxide is prepared by dehydrohalogenating dichlorhydrins of 4-vinyl cyclohexene by treating with the hydroxide or carbonate of an alkali or alkaline earth metal, in an aqueous medium. Any temperature from the freezing point to the boiling point of the reaction mixture may be used but the preferred temperatures are 25 DEG C. and lower. The resulting dioxide may be isolated by extraction with a solvent for the dioxide which is unattacked by the oxide, e.g. chlorinated hydrocarbons, ether and aliphatic and aromatic hydrocarbons. The dichlorhydrins may be prepared as described in Specification 648,456. The following are representative of numerous examples: (1) a hypochlorite solution obtained by passing chlorine into an aqueous suspension of calcium carbonate followed by filtration, is added over a period to a stirred suspension of 4-vinyl cyclohexene in water at below 10 DEG C. and the resulting dichlorhydrins are isoated by ethereal extraction; the dichlorhydrins are added to aqueous sodium hydroxide with stirring at 25 DEG C. and the resulting dioxide isolated by extraction of the mixture with carbon tetrachloride; (4) chlorine is bubbled through an aqueous solution of sodium hydroxide at 3 DEG C. and to the resulting solution of hypochlorite is added 4-vinyl cyclohexene and then aqueous sulphuric acid sufficient to liberate most of the hypochlorous acid from the hypochlorite; aqueous sodium hydroxide is now added and sufficient sodium sulphite to decompose the excess hypochlorite, and the 4-vinyl cyclohexene dioxide produced is extracted as before; (8) chlorine gas is bubbled through aqueous sodium hydroxide at 3 DEG C., the resulting solution added slowly to a dispersion of 4-vinyl cyclohexene in aqueous sulphuric acid at not above 10 DEG C., then aqueous sodium hydroxide is added; the mixture is extracted with carbon tetrachloride and the extract distilled at 5 mm. pressure to isolate the dioxide, quantities of 4-vinyl cyclohexene monoxide appearing in the fore-runnings; (9) a hypochlorite solution obtained as in (8) is added slowly with vigorous stirring to a suspension of 4-vinyl cyclohexene in aqueous sulphuric acid at below 10 DEG C., the addition being stopped when test shows that hypochlorous acid is not rapidly taken up; at this stage an oil appears containing monochlorhydrins, so a solvent, ethylene dichloride, is added and addition of the hypochlorite continued; aqueous sodium hydroxide is then added and the dioxide is recovered from the ethylene dichloride layer; (11) chlorine is passed into an aqueous suspension of 4-vinyl cyclohexene until a positive test for hypochlorite persists, whereupon excess hypochlorite is decomposed by addition of sodium sulphite, and the dichlorhydrins converted to dioxide by addition of sodium hydroxide. The Specification as open to inspection under Sect. 91 refers to the preparation of 4-vinyl cyclohexene dioxide from the dichlorhydrins by dehydrohalogenation in general. This subject-matter does not appear in the Specification as accepted.