Synthesis Of Trans-4-phenylcyclohexanol By Catalytic Hydrogenation

Trans-4-phenylcyclohexanol is an important commercial intermediate of 4-(p-Bromphenyl)-cyclohexanon.Synthesis of trans-4-phenylcyclohexanol by hydro- genation of 4-phenylphenol is studied in this paper.The effects on selectivities were investigated by the change of different catalyst, temperature, pressure,catalyst dosage,pH,stirring speed,solvent and time. Results showed that selectivity of trans-4-phenyl cyclohexanol was up to 39.89% under the reaction conditions of temperature 50℃, pressure 0.5～1.0Mpa ,stir rate 800r/min, using W-7 Raney-Ni as the catalyst (material propotion 3:1)and ethanol as the solvent for 6 hours. The final product was obtained by chromatography with the mixture of V (tetrachloride) :V (ethylacetate) =8.0:2.5 on silicagel, and the yield was up to 37.15%.The purity was 100% analyzed by gas-chromatography, and the configuration of the aimed-product was affirmed by IR .The mechanism of catalytic-hydrogenation of 4-phenylphenol was researched at the same time. Results showed that all of original compound was hydrogenated to monosubstituted benzene and 1,4-disubstituted benzene respectively,amount of the former was larger when Raney-Ni was used as a catalyst, and subsequently intermediates were hydrogenated to full reduced products.There might be an isomerization between enol and ketone at higher temperatures.Langmuir course expresses the process well at the temperature 323K and the pressure from 0.5～1.0Mpa. The apparent kinetics is evaluated by simulation of the experimental data ,and the order of all reactions is first,kinetic equations of principal and secondary reactions are as follows: secondary reactionsActivation energy is 20.2KJ/mol. principal reaction r_B = ddCtB= k₁ C A-k₄C_Br_D =k₃ C_Ar_F =k₅C_Cr_E =k₄C_Bk₁ = 0.28h^-1 , k₂ = 0.18 h^-1 , k₃ = 0.1383h^-1 , k₄ = 0.0303h^-1 , k₅= 0.0256h^-1 Activation energy is 20.2KJ/mol.