Studies On Synthesis Of 1,2-Dipheylethane From Benzyl Chloride

1,2-Diphenylethane is an important intermediate, it is an excellent leather tanning agent when it is sulfurized and important raw material for the preparation of fluorescent brightener and dye when it is dehydrogenated. Recently, it has been used further because a new type of high-efficiency flame retardant, dicabromodipheylethane, was developed successfully. At the same time, it can be used not only as an important product of organic chemical industries, but also an heat transfer oil in the pharmaceutical industries for its good properties of heat transfer and thermal stability. Nowadays, there are many ways to synthesize 1,2-Dipheylethane, however, those which can be industrialized can be grouped into two categories : one of which to prepare 1,2-Dipheylethane is by alkylation's reaction from benzene and alkylation agent under the catalyzer of AlCl3, the raw materials are cheap and the yield is high, however, the reaction conditions are harshness for it should be carried out under the anhydrous condition, at the same time, the problems of pollution and erosion due to HCl are unavoidable and all these can improve the producing costs; Another is a coupling reaction of Benzyl Halogenation, the technology is simply and the reaction conditions are easy to control, while, the yield is much higher and the problems of pollution have been abated, the shortcoming of this technology is that the cost of material, Benzyl halogenation, is higher, therefore the key to the synthesis of 1,2-Dipheylethane is how to improve the conversion rate of Benzyl halogenation and decrease the producing costs. This paper studies the technology for the preparation of 1,2-Dipheylethane from Benzyl Chloride and Fe under the catalyzers of Cu and Cu₂Cl₂, the method for the analysis raw material together with product by high-performance liquid chromatograph is built up. With the orthogonal and single factor experiment, the effect of the composition of raw material, reaction medium, reaction temperature, reaction time on the reaction had been studied and the optimum reaction condition have been taken. The optimum reaction condition is: the amount of catalyst is Cu0.3g,Cu₂Cl₂0.4 g;reaction temperature is 80-85; the composition of raw material is nFe/nBenzyl Chloride =0.56 and reaction medium is water. The yield of 1, 2-Dipheylethane is beyond 95% under the optimum reaction condition, The law of reduce-condesate reaction has been discussed according the results of experiments. Based on the reasonable hypothesis and simplification, mechanism A, which is considered that 1,2-Dipheylethane is directly produced from (CuCH₂Ph)⁺ and Benzyl Chloride, and B, which is considered that 1,2-Dipheylethane is produced from two·CH2Ph decomposed from CuCH2Ph+ , on Benzyl Chloride reduce-condesate reaction have been presented according to some references and macro-reaction kinetic models have been proposed. By the analysis of mechanism and the comparison of calculated value of model to experiment value, the mechanism B is more suitable to interpret the true-process of reaction.