Optimizing the extraction of 2-aminopyrimidine

Abstract

UDC 615.31.547.853.3].012.1 One of the intermediate products in the synthesis of sulfadiazine is 2-aminopyrimidin e, which is isolated from the reaction solution by extraction With methylene chloride. For the extraction, we employed an E-400-TF horizontal countercurrent extractor, using a multiple countercurrent scheme. In the process, the working phases, viz., the aqueous (a solution containing 2-aminopyrimidin e) and the organic (methylene chloride) were passed through the extractor 3-6 times (3-6 cycles) at preset volume ratios. The choice of a multiple countercurrent scheme was due to the low and variable partition coefficient of 2-aminopyrimidin e (0.3-1.6) and the extraction efficiency of the extractor, which allowed attaining approximately two equilibrium levels under the experimental conditions. Laboratory investigation of the kinetics and statics of the extraction of 2=aminopyrimidin e from reaction solutions obtained using various amounts of oxidant (1050%) preceded work with the extractor. The goal of the present investigation was to optimize the extraction by the method of mathematical planning of the experiment [1, 2]. The yield of 2-aminopyrimidin e at the extraction stage was chosen as the optimization parameter (y). The fundamental factors which affect the process are: X 1 = the ratio of the reaction mixture volume to the methylene chloride volume; X 2 = the number of extraction cycles; X 3 =the concentration of the salt additive; X 4 = the oxident concentration; X 5 = the pH of the reaction mixture. The conditions which were used at the start of this work were characterized by the indexes: X 1 = 1:0.5; X2=3; X 3=0%;X4=50%;X 5=9.0. Y=85%. The levels of the factors we selected and their variation intervals are presented in Table 1. To optimize the process, we decided to use 1/4 replicas of the entire factor of the 25 experiment. The matrix for planning the experiments and the results obtained are presented in Table 2.