GB569373A - Process for the manufacture of unsaturated ketones - Google Patents

Abstract

Unsaturated ketones of the formula <FORM:0569373/IV/1> wherein R is an alkyl, aryl or cycloalkyl group, are prepared from a substituted butinol of the formula <FORM:0569373/IV/2> by hydration and dehydration in either order. Hydration is effected by the action of aqueous mercuric, silver or cadmium salts with, if desired, boron trifluoride, and dehydration with chemical dehydrating agents such as phosphorus pentoxide, anhydrous oxalic acid or 30 per cent sulphuric acid or dehydration catalysts such as activated alumina or active charcoal impregnated with phosphoric acid. Dehydration gives a substituted vinyl acetylene, <FORM:0569373/IV/3> which on hydration yields the desired ketones. Alternatively, hydration of the substituted butinol gives a hydroxy-ketone, <FORM:0569373/IV/4> which on dehydration yields the same ketones. The products are converted into substituted acrylic acids with aqueous hypochlorite solution. Methyl, ethyl, butyl, phenyl, and cyclopentyl are specified as examples of R. In examples: (1) 3-methyl-1-butine-3-ol is heated with 30 per cent sulphuric acid to 83 DEG C. when methovinyl acetylene distils. This is heated with aqueous mercuric sulphate solution to 100 DEG C. under pressure. The upper layer is distilled in the presence of hydroquinone as an anti-oxidant to give 3-methyl-3-butene-2-one; (2) 3-methyl-3-hydroxy-2-butanone is prepared by adding methyl butinol to a solution of mercuric oxide, sulphuric acid and water while steam distilling. To the product, phosphorus pentoxide is added at 0 DEG C., followed by heating to 80 DEG C. for 3 hours and distillation to give the same product. Hydroquinone is present as in (1) ; (3) 3-methyl-3-butene-2-one is added to sodium hypochlorite solution at 10 DEG C. and methacrylic acid separated as such or esterified directly, e.g. with butyl alcohol.