Effective Use of Phase Transfer Catalyst in a Third Phase.

Repeated use of a phase transfer catalyst was studied. The catalyst (hexadecyl tri-n-butyl phosphonium bromide) was concentrated in a third phase (referred to as a middle phase) which was developed between the organic phase and the aqueous phase. The middle phase was observed only when dodecane was used as an organic phase and the aqueous phase was saturated with pottasium bromide. The middle phase could catalyze the substitution reaction of benzyl chloride with Br-, the former was located in the organic phase and the latter in the aqueous phase. After the reaction was completed, the reaction mixture (organic phase) was removed and a new organic phase was charged. By this operation, the middle phase could be used repeatedly.A new operation method was investigated in order to avoid direct contact between the organic phase and the aqueous phase. The three phases were settled without stirring and the transfer of the reactants was promoted by ultrasonic waves through the interface of the phases. The middle phase catalyzed the reaction by this ultrasonic operation.