The Study On The Racemization Technology Of The D-tetramisole Dissociation Alkali

The levamisole hydrochloride which was also called Tetramisole is a kind of important medical intermediate and broad-spectrum nematocide. The tetramisole hydrochloride is the mixture of the levamisole and the D-tetramisole. A half part of the general Tetramisole medicine is impure . So it has a little action to repell the eelworms but has heavy toxicity. The best measure to repell the eelworms is to use the pure L-tetramisole. But in actually the L-tetramisole can't exist by itself. It exists as the racemate with the D-tetramisole. So the separation of the tetramisole to get pure L-tetramisole is very important. The separated D-tetramisole was transformed to the racemate by the way of racemization. Then the racemate was separated again and again. The pure L-tetramisole was obtained by the way of racemization and separation repeatly in the traditional industry. The alkaline condition was used in the traditional racemization process. Also the dimethyl sulphoxide was used as the solvent in traditional racemization process. The solvent costed too much money and had heavy pollution to the environment and the body. So it's necessary to seach a new racemization process to reduce the pollution and the cost. In this thesis, a new racemization process which has less pollution and lower cost was found through many experiments. The technological processes are listed as follows:1. The mixture of the water and ethanol was used as the solvent in the racemization reaction and the best conditions were obtained (the added quantity of D-tetramisole dissociation alkali was 20g): the reaction temperature is 80°C; the racemization time is 2 hours; the volume of ethanol solution is 40mL; the mass of sodium hydroxide is 4.0g; the proportion of ethanol and water is 3:1. The new process has more advantages than the traditional one: it has smaller pollution to the surrounding and the body and also it has more extensive raw material source and lower cost. So the new process has the positive meaning of environmental protection and the improvement of technique.2. The methyl alcohol was used as the solvent in the separation process, and the best processing conditions were obtained ( the added quantity of the racemate was 40g ): the volume of the methyl alcohol is 100mL; the temperature of the sediment separated out is 0°C; the pH of the salify is 3.