INVESTIGATING THE REACTION KINETICS FOR OBTAINING DIPHENHYDRAMINE

Abstract

Diphenhydramine (Dimedrol) is one of the main representatives of the group of first generation antihistamines, which is still actively used for some allergic diseases of the central nervous system. The chemical name is N,N-dimethyl-2-(diphenylmethoxy)- ethylamine (as hydrochloride). Previously we have studied the alkylation of monoethanolamine under conditions of phase transfer catalysis. The aim of this work is the research of kinetic regularities of the alkylation of dimethylamineethanol. Diphenylchloromethane (benzohydrochloride) was used as an alkylating agent. The reaction was carried out in a two-phase liquid-liquid catalytic system. Also, the kinetics of the reaction by O-alkylation of dimethylamineethanol for the synthesis of N,N-dimethyl-2- (diphenylmethoxy) ethylamine by phase transfer catalysis was studied in detail. A quaternary ammonium salt was used as a phase transfer catalyst: tetrabutylammonium chloride, which is an available catalyst. To determine the coefficients of the kinetic equation, a full-factor experiment of dimension 2³ was implemented.

The concentration of the catalyst - trimethylbenzylammonium - chloride in all experiments was 0.1 mol/l ^–1, 1.5 times higher than the critical micelle concentration. Independent variables varied in the intervals: temperature: 60...80⁰C and the initial concen- trations of benzohydrochloride and dimethylamineethanol - in the range of 1.5  2.0 mol/l.

The analysis of the obtained kinetic equation was carried out using the SimuLink, ver. 4.0 in the MatLab 6.5 system. The ratio of reagents has been shown to have a much stronger effect on the reaction rate than the values of their initial concentrations. The resulting kinetic equation can be used to calculate the reactor for the production of N,N- dimethyl-2-(diphenylmethoxy)ethylamine.