GB681990A - Oxidation of aromatic hydrocarbons - Google Patents

Abstract

Compounds of the formula Ar-CHR1R2 (R1 and R2 are alkyl and Ar is aryl or alkaryl) are oxidized by passing in an oxygen-containing gas in the liquid phase at 20-95 DEG C. at atmospheric pressure or above 95 DEG C. at superatmospheric pressure in the presence of water or aqueous alkali, the ratio of aqueous medium to oxidant being less than 1 : 1 by weight, e.g. 1 : 10-1 : 3. The alkali may be a metal hydroxide (e.g. sodium, potassium, lithium, calcium or barium), an organic base (e.g. a tetraalkylammonium or trimethylbenzylammonium hydroxide), a metal carbonate or bicarbonate (e.g. sodium) or an alkali metal salt of a weak organic acid. There may be used as catalyst activated carbon or a metal salt, which may be water-soluble such as potassium permanganate potassium stearate, manganese acetate, ferrous sulphate, cobalt nitrate or cobalt acetate, or oil-soluble such as manganese linoleate or manganese butyl phthalate. The products are mainly alcohols Ar-CR1R2OH or peroxides Ar-CR1R2OOH, depending on the reaction conditions, but dihydric alcohols, acids and ketones may also be obtained. Low temperatures, absence of alkali, and high catalyst concentration favour the production of alcohols whereas high temperatures with alkali and little or no catalyst give high yields of peroxides. The reaction is facilitated by the addition of an organic peroxide as initiator, e.g. one of the oxidation products dissolved in unchanged starting material. The reaction mixture is separated into the aqueous and oily layers, the former being acidified to precipitate organic acids. The oily layer is alkali-extracted to remove acids and, if desired, fractionally distilled under reduced pressure. If peroxides are not required, they may be decomposed by heat before the mixture is distilled. In the examples: p-cymene is oxidized to p-methylacetophenone, p-tolyl-dimethylcarbinol and the corresponding hydroperoxide and cumic and other acids, e.g. p-toluic and terephthalic; cumene is oxidized to phenyl-dimethylcarbinol and the hydroperoxide, acetophenone and other unspecified products; di-isopropylbenzene yields p-isopropylphenyl-dimethylcarbinol and the hydroperoxide, p-isopropylacetophenone, p-acetylphenyl-dimethylcarbinol, p-phenylene-bis-dimethylcarbinol and the corresponding bishydroperoxide; sec.-butylbenzene gives acetophenone and phenylmethylethylcarbinol. Other specified starting materials are those in which the aryl nucleus is naphthalene, anthracene or phenanthrene and/or is substituted by methyl, ethyl, propyl, isopropyl or any of the butyl groups. Similarly R1 and R2 may be any of these alkyl groups and may be the same or different. If the starting material is a solid it is dissolved in a solvent such as benzene. Specifications 610,293, 616,330, 630,286, 641,250 and 654,035 are referred to.ALSO:Hydroperoxides obtained by oxidizing compounds of the type Aryl-CH (alkyl)2 (see Group IV (b)) are useful in kier boiling, bleaching and other textile operations. a a -Dimethylbenzylhydroperoxide is specified. The corresponding alcohols are good wetting-out agents.ALSO:Products obtained by oxidizing compounds of the type Aryl-CH(alkyl)2 (see Group IV(b)) are used as perfume bases for soaps. Phenyldimethylcarbinol p-tolyldimethylcarbinol and the ketones produced in the oxidation are especially suitable.ALSO:Products obtained by oxidizing compounds of the type Aryl-CH(alkyl)2 (see Group IV(b)) are used for separating materials by flotation. Thus p-tolyl-dimethylcarbinol is a frothing agent for copper, zinc and lead sulphide ores; phenyldimethylcarbinol and the dihydric alcohols such as those derived from di-isopropylbenzenes have similar applications, as well as the corresponding hydroperoxides. Alkali salts of cumic acid may be used in the separation of potassium and sodium salts by flotation.ALSO:Hydroperoxides obtained by oxidising alkyl substituted aromatic compounds of the formula <FORM:0681990/V/1> in which R1 and R2 represent alkyl groups, and Ar an aryl or alkaryl group (see Group IV (b)), are useful in rubber reclaiming; a a -dimethylbenzyl hydroperoxide is specified.