Two-phase Wittig reaction of synthesizing liquid crystal intermediate by active quaternary phosphonium salt

In this work, (4-methyl) methyl benzoatyltriphenylphosphonium bromide (BrPPh3CH2C6H4COOCH3, MBPB), which was prepared from the reaction of (4-bromomethyl) methyl benzoate BrCH2(C6H4) COOCH3 and triphenyl phosphine (PPh3) in a CH2Cl2/H2O two-phase medium in the laboratory, acted as the active reagent to synthesize methyl {4-[ 4-(nonyloxy)-styryl]} benzoate in Z- and E-form (n-C9H19O(C6H4) CH=CH(C6H4) COOCH3, MNSB). The product is a useful liquid crystal intermediate used in industries. Through the active reagent, MNSB is synthesized from the reaction of 4-nonyloxybenzoic aldehyde (n-C9H19O(C6H4) CHO, NAOD) in an alkaline solution of NaOH/ organic solvent two-phase medium. The reaction is largely enhanced in the presence of MBPB compound as the active reagent in the Wittig reaction. Under most reaction conditions, this reaction is favorable for the production of E-form MNSB product rather than forming the Z-form MNSB product. A kinetic model was developed and a pseudo-first-order rate law was found to be sufficient to express the kinetic behaviors of the reaction. Effects of the reaction conditions, including the agitation speed, the temperature, the reactant concentration, the organic solvents, the sodium hydroxide concentration, and the 4-nonyloxybenzoic aldehyde concentration on the conversion of NAOD and the reaction rate were investigated in detail. Rational explanations to the observed results have been made.