Study on the Synthetic Process of Vat Pink R
|School||Changsha University of Science and Technology|
|Keywords||dyestuff vat pink R organic synthesis o-toluidine 6-chloro-4-methyl-1，3，2-benzothiazathiolium hydroxide synthetic process|
The vat pink R is a widely used in the printing of towels and bedding bags and preparing the vat pink S-3B, it has the extremely widespread use. As the dye is the bright color, excellent leveling property and good fastness,so it is deeply welcomed by domestic and foreign users and the high-demand goods in the present market.The synthetic process of vat pink R has been protected abroad by patent, while currently the domestic process of vat pink R is not yet ripe with relatively high production costs. So study on the synthetic process of vat pink R has a very important significance in order to reduce the production costs. Herein, based on literature survey, this paper has focused on studying on Synthetic process of Vat Pink R Intermediate 6-Chloro-4-methyl-1,3,2-benzothiazathiolium hydroxide. The studies are summarized as follows:1. 6-Chloro-4-methyl-1,3,2-benzothiazathiolium hydroxide, a key intermediate for vat pink R, was successfully synthesized via salification, sulfurization and hydrolyzation from o-toluidine as the start material. LC/MS, 1HNMR and IR spectra confirmed the chemical structure of the product. The purity of the product was 97.8%, with the yield 95.0%. The process possessed the merits of simple operation, less cost required, higher yield, higher purity and so on, therefore, the industrialization production is so easy. 2. The deficiencies in the synthetic process of 6-Chloro-4-methyl-1,3,2-benzo thiazathiolium hydroxide in view of the literature were improved via large quantity of exploratory and parallel experiments. During the process of preparing o-toluidine hydrochloride, the process was simplified and the cost was reduced by using concentrated hydrochloric acid to replace the gas of hydrogen chloride. And then, various reaction conditions, such as the molar ratio, recrystallization to the filtrate of salification and so on, were discussed to improve the average yield of o-toluidine hydrochloride. After this, the average yield was improved by 19.4% as compared with the value reported by references. During the process of synthesizing 6-Chloro-4-methyl-1,3,2-benzothiazathiolium hydroxide, the process was simplified and the cost was reduced by using the method of o-toluidine hydrochloride. And then, various reaction conditions, such as molar ratio, reaction temperature and so on, were discussed to reduce the by-products, so the process of separation and purity could be avoided. On the other hand, reaction time of hydrolyzation was shorten and the amount of hydrochloric acid in waste water was signficantly reduced by using 5% sodium acetate solution to replace water. Moreover, reaction time of hydrolyzation and so on, were discussed to improve the efficiency and yield of hydrolyzation. After this, the yield was improved by 5.6% as compared with the value reported by references. From the above mentioned of improved synthesis, the total yield of 6-Chloro-4-methyl-1,3,2-benzothiazathiolium hydroxide was increased by 23.0%( o-toluidine as measurement).3. Based on the summary of literature and the synthetic process of vat pink R on productive enterprises, vat pink R was synthesized via condensation, diazotization, cyanidation, alkaline hydrolyzation, acid hydrolyzation, oxidation from 6-Chloro-4-methyl-1,3,2-benzothiazathiolium hydroxide as the material. All in all, based on the synthesis of reactions by 9 steps, the total yield of vat pink R was 62.6% that increased about 15.2% (o-toluidine as measurement), so the cost was Significantly reduced.