Wittig Reaction of Synthesizing Liquid Crystal Intermediate by Novel Phase-Transfer Catalysis

Maw Ling Wang, Department of Environmental Engineering, Hung Kuang University, Chung-Che Road, Taichung County, 433, Taiwan and Shan-Je Lin, Department of Chemical Engineering, National Tsing Hua University, No. 101, Kuang-Fu Road, Section 2, Hsinchu, 300, Taiwan.

In this work, (4-Methylmethylbenzoatyltriphenyl phosphonium bromide (MBPB) was synthesized from the two-phase reaction of (4-methyl)methyl benzoate BrCH2(C6H4)COOCH3 and triphenyl phosphine (PPh3) in a CH2Cl2/H2O two-phase medium. Methyl 4-(4-(nonyloxy)(Z)-styryl) benzoate, which is a useful liquid crystal intermediate, is synthesized from the reaction of 4-nonyloxybenzoic aldehyde in an alkaline solution of NaOH/organic solvent two-phase medium. The reaction is largely enhanced in the presence of (4-methyl)methylbenzoatyltriphenylphosphonium bromide (MBPB) which is synthesizied from the laboratory in the present work, as the novel phase-transfer catalyst in the Wittig reaction. Under this reaction conditions, the reaction is favorable for the production of Z-form product rather than E-form product. A kinetic model was developed and a pseudo first order rate law is sufficient to express the kinetic behaviors of the reaction. Effects of the reaction conditions, including agitation speed, temperature, reactant concentration, organic solvents, sodium hydroxide concentration and 4-nonyloxybenzoic aldehyde concentration on the reaction rate were investigated in detail. Rational explanations are made for the peculiar results satisfactorily.