In accordance with the present invention, (1-phenylethyl) hydroquinone is synthesized by reacting styrene with hydroquinone in the presence of an organic diluent and in the presence of effective reaction stimulating amounts of a Lewis acid. The crude (1-phenylethyl) hydroquinone reaction product and unreacted reactants are then vacuum distilled to obtain a fraction consisting primarily of the (1-phenylethyl) hydroquinone. The vacuum distillation is done in the presence of an organic diluent which co-distills with unreacted hydroquinone under the conditions of vacuum distillation. Exemplary of suitable Lewis acids are: para-toluene sulfonic acid, sulfuric acid, boron trifluoride, hydrofluoric acid, stannic chloride and aluminum trichloride.
Desirably, the diluent is an ether, for example, a lower (C.sub.1 -C.sub.5) alkyl ether including, for example, ethyl ether and tetrahydrofuran, and most desirably, a liquid polyether like the dialkoxy tetraglycols wherein the alkoxy group contains up to four carbon atoms. Other diluents include halogenated benzenes, for example, tribromobenzene, hexadecane, pentadecane and octylether. The diluent employed during the reaction (reaction diluent) will be a solvent for the reactants and the products, and as indicated above, preferably will be an ether. Desirably, the material has a boiling point in excess of about 135.degree. C. By performing the reaction in a reaction diluent, good yields are obtained. By using a desired organic diluent during distillation (distillation diluent), a practical benefit is obtained and a problem is solved. The distillation diluent is selected to co-distill with hydroquinone so as to allow for the recovery of substantial amounts of the monosubstituted material and at the same time prevent plugging of the distillation column by the hydroquinone. The reaction is done at a suitable temperature and for a suitable time effective to form the product and preferably is conducted at approximately 135.degree. C. to about 145.degree. C. for several hours. The crude product is purified by high vacuum batch distillation. Generally, the organic diluent employed during distillation will have a boiling point in the range of about 270.degree.-290.degree. C. and it is generally preferred to use as the reaction diluent material that will function as the distillation diluent. In the preferred technique, the diluent will be tetraethyleneglycol dimethylether, that is, a material of the formula CH.sub.3 (OCH.sub.2 CH.sub.2).sub.4 OCH.sub.3 (also known as dimethoxytetraglycol) which is commercially available under the trade designation Tetraglyme material. The preferred Lewis acid is para-toluene sulfonic acid, and, in this case, it is preferred to purify the crude (1-phenylethyl) hydroquinone product by distillation employing sodium hydrogen sulfite, or other alkali metal hydrogen sulfite, to neutralize the para-toluene sulfonic acid catalyst and prevent oxidation of hydroquinone and the synthesized (1-phenylethyl) hydroquinone to quinones.
Since an object of the present invention is to form the monosubstituted i.e., (1-phenylethyl) hydroquinone in high yields, the stoichiometry employed will generally be about an equimolar amount of hydroquinone to styrene and preferably a slight molar excess of hydroquinone to styrene. Accordingly, desirable molar ratios of hydroquinone to styrene will be about 1:1 to about 1.20:1 or even 1.25:1 if desired.
The (1-phenylethyl) hydroquinone produced in accordance with the present invention is ideally suited as a reactant for a wide variety of chemical reactions wherein the mono substituted diol is needed. It is especially useful in producing polyester resins in the manner set forth in the above incorporated U.S. patent application Ser. Nos. 581,166 and 819,945.