GB778974A - Process for the manufacture of carbinols - Google Patents

Abstract

Carbinols are manufactured by reacting organic hydroperoxides containing the same number of carbon atoms as the desired carbinol, under liquid conditions, with hydrogen, using palladium supported on activated alumina as a catalyst. The catalyst may be prepared by impregnating activated alumina with an aqueous solution of a palladium salt and reducing the resulting mixture either by treating with formaldehyde, or another reducing agent, or by conducting hydrogen over it. The liquid conditions are produced by either working at a temperature at or exceeding the melting point of the hydroperoxide, when it is a solid at temperatures below 80 DEG C., or by dissolving wholly or partly in a liquid solvent, at the required temperature. Suitable solvents are water, alcohols, hydrocarbons, and some ketones, ethers and esters either alone or in admixture. It is preferable to use either the initial compound from which the hydroperoxide is obtained, or a solution of the hydroperoxide as obtained from the initial compound by autoxidation for the solvent. The hydroperoxide so used may be dispersed or suspended in a liquid in which it is not soluble. The optimum pH is between 7 and 12 the optimum temperature 40-120 DEG C. and the optimum amount of catalyst 1-20 per cent (containing 0.7 per cent palladium) by weight of the hydroperoxide used. The reaction ceases with the formation of the carbinol. At the end of the reaction the catalyst settles at the bottom of the reaction vessel and the reaction mixture may be withdrawn and the catalyst used again. The carbinol may be separated from the solvent and water of reaction by simple separation, by azeotropic distillation or by use of a dehydrating agent, e.g. sodium sulphate. The process may be applied to aromatic, aliphatic, and substituted aromatic mono- or dihydroperoxides, to form the corresponding carbinol. In an example for the preparation of phenyldimethyl carbinol, the catalyst is prepared by dissolving palladous chloride in N/10 hydrochloric acid and heating to 70 DEG C. The solution is then added to a suspension of chromatographic alumina in water, and aqueous formaldehyde added, followed after a few minutes by sodium bicarbonate. The mixture is left standing for 30 minutes at a temperature of 70 DEG C. and the catalyst washed by decantation, filtered and dried. Crude isopropylbenzene hydroperoxide and some sodium carbonate, together with the catalyst moistened with isopropylbenzene hydroperoxide, are mixed, and stirred in the reaction vessel after the air has been removed by hydrogen. Hydrogen is passed into the vessel until absorption ceases, when the reaction mixture which has settled out, is removed by suction through a filter disc. The removed hydrogenated hydroperoxide is replaced by the crude hydroperoxide. The phenyldimethyl carbinol is recovered after decanting from the water of reaction, and fractional distillation. Examples are also given for the preparation of m-(1-hydroxy 1-methyl ethyl) isopropyl benzene, m-di-(1-hydroxy 1-methyl ethyl) benzene, 1-hydroxy 1-methyl-n-propyl benzene and 1,3,3-trimethylindan-1-ol. The stability of the catalyst is illustrated with an example demonstrating that no loss in catalytic activity occurs in 18 days.