CS265262B1 - Process for preparing di-tercbutylhydroxybenzenes - Google Patents

Abstract

Process for preparing di-tert-butyl dihydroxybenzenes of formula I by alkylation of the corresponding dihydroxybenzenes with tert-butyl methyl ether in the presence of a catalyst, preferably sulfuric acid at 0 to 70 ° C in excess tert-butyl methyl ether optionally in an inert inert solvent.

Description

The present invention relates to a process for the preparation of di-tert-butylhydroxybenzenes by alkylation of the corresponding dihydroxybenzenes with tert-butyl methyl ether.

Substituted divalent phenols, i.e. hydroquinone, resorcinol and pyrocatechin, which contain bulky carbon-substituted alkyl substituents in the molecule, are capable of reacting with free radicals and interrupt or retard radical reactions. Particularly important in this regard are the hydroquinone derivatives, which are widely used as stabilizers and antioxidants for stabilizing vegetable and animal fats, saturated and unsaturated hydrocarbons and mixtures thereof, lubricants, gasolines, monomers, sensitive organic substances of various character, organic polymers, synthetic rubbers, of photographic emulsions and s ..

These compounds are prepared either by alkylation of divalent phenols with isobutylene under catalysis with concentrated sulfuric acid, where isobutylene is used directly or is prepared by dehydration of tertiary butanol, or a target is used for alkylations. butyl halides, mostly target. Butyl chloride and alkylation are carried out under catalysis of zinc, ferric or aluminum chloride mostly in ethanol environment.

The disadvantage of these processes is that isobutylene (2-methylpropene) is practically unavailable for normal laboratory practice or small-scale production, moreover it is a gas at normal temperatures and the work with it presents necessary and sometimes quite complex technical modifications of the equipment. The second tert-butyl halide method uses relatively expensive and not quite common chemicals. Also, the processing of the reaction mixtures in both processes and the isolation of the products is not easy.

The above-mentioned drawbacks of the hitherto known processes are solved by the present invention, which relates to a novel process for the preparation of di-tert-butyldihydroxybenzenes. The invention consists in that the alkylation is carried dihydroxybenzenes respective terč.butyIraetyleterera an acid catalyst, preferably concentrated sulfuric acid at 0 to 70 C, ^e terc.butyImetyleteru in excess, optionally in a co-solvent inetrním.

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A practical embodiment is to prepare a solution of dihydroxybenzene in a mixture of an inert solvent and the necessary amount of tert-butyl methyl ether and add a small amount of concentrated sulfuric acid dropwise with stirring or to add another suitable catalyst. minutes, the product precipitates from the mixture in crystalline form and can be easily isolated. The reaction proceeds easily even without heating at ordinary temperature. Suitable inert solvents are, in particular, liquid aliphatic hydrocarbons or gasoline, but other inert substances such as, for example, chlorinated solvents, aromatic liquid hydrocarbons such as toluene or xylene, but also acetic acid can be used. The reaction is catalyzed not only by sulfuric acid, which is advantageous because of its availability and yields, but other acidic catalysts such as other inorganic and organic acids such as dodecylbenzenesulfonic acid, p-toluenesulfonic acid, but also Lewis acids can be used. acids ..

Detection and control during the reaction, a qualitative analysis of the product can be done easily by thin layer chromatography, for example on the plate 254 and Silufol UV detection under UV light with the production of the system cyclohex ^- an-acetoh 3: 1 ·

The following examples describe the reaction. Parts are by weight.

Example 1

150 parts of hexane were charged to the reactor and 60 parts of tert-butyl methyl ether were charged. To this solution, 27.5 parts of resorcinol was added with stirring, and after dissolution, 5 parts of concentrated sulfuric acid were added dropwise at 20 ° C over a half hour. The temperature rose slightly to 25 ° C, after half an hour the solution was heated to 35 ° C for another half hour. To the reaction mixture thus obtained, 150 parts of water at 40 ° C are added with stirring, and a pale pink substance is formed by stirring. It is suction filtered, washed with water so that all the pink product is washed off and the substance remains pure white. The product is then dried in a hazel drier. The yield of pure white crystalline material, 4,6-di-tert-butyl resorcin, is 89%, m.p. 121 DEG-3 DEG.

Example 2

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180 parts of light petroleum were charged to the reactor, to which 50.2 parts of tert-butyl methyl ether were added, which is about 10% excess for the reaction. The resulting mixture was charged with 27.5 parts of hydroquinone and dissolved in 20 minutes. 45 parts of concentrated sulfuric acid are added dropwise · The temperature rises to 35 ° C · At the end of the dropwise addition, the solvent layer begins to harden with the precipitated product · After the addition of sulfuric acid is added, the temperature is increased to 45 ° C. and then the precipitated product is filtered off with suction. Wash with about 600 parts of water on the sucker and remove. 129 parts of a wet paste of the product are obtained, which after drying in a hazel oven is 96 parts. The product forms bright white needles with a melting point of 218 ° C. The 2,5-di-tert-butylhydroquinone prepared was obtained in a yield of 86.4% of theory. '

Example 3

200 parts of n-heptane were charged to the reaction flask and 50.2 parts of tert-butyl methyl ether were added. 27.5 parts of pyrocatechin were dissolved in this mixture. A total of 25 parts of concentrated sulfuric acid was then added in small portions at 10 ° C over 1 hour. After the addition was complete, the reaction solution was heated to 50 ° C and stirred at this temperature for 1 hour. After cooling to 20 ° C and seeding the product, 3,5-di-tert-butylpyrocatechin precipitated in the form of colorless plates, m.p. 96 ° <g 98 ° C, obtained by aspirating the reaction mixture, washing the filter cake 300. The reaction yield is 39.7 parts, which corresponds to 72% of theory.

Claims (1)

SUBJECT OF THE INVENTION 265 262 Process for preparing di-terc.butyldihydroxybenzenů following formula / CH _3/3 -C / CH _3/3 -C appropriate alkylation of dihydroxybenzenes, characterized in that the alkylation is carried out in the presence of t-butylmethyl acid catalyst, preferably concentrated sulfuric acid at 0 ° to 70 ° C in excess tert-butyl methyl ether, optionally in an auxiliary inert solvent.