Synthetic method of dithiobenzoic acid

Abstract

The invention discloses a synthetic method of dithiobenzoic acid. According to the synthetic method disclosed by the invention, the technical measures: introducing an inert gas, stirring, and the like for the control of the dispersion morphology of reaction raw material sublimed sulfur at the early stage of synthesis and the elimination of water and oxygen in a reaction system are adopted by researching the traditional synthesis conditions of the dithiobenzoic acid, and therefore, the problems that the sublimed sulfur and benzyl chloride are easy to generate side reaction with the oxygen contained in air before being reacted in the prior art are prevented, the sufficient reaction of the sublimed sulfur and the benzyl chloride is ensured, the synthesizing yield of the dithiobenzoic acid is greatly increased, the transformation rate of the dithiobenzoic acid can reach about 81 percent, the time of the integral process is shortened to about 16 hours, the production efficiency is greatly enhanced, the production cost is reduced and a simple, convenient and efficient way is provided for the synthesis of the dithiobenzoic acid widely used for the preparation of a segmented copolymer.

Description

technical field [0001] The invention belongs to the technical field of preparation of dithiobenzoic acid, in particular to a synthesis method of dithiobenzoic acid. In the field of polymers, it is mainly used as a synthetic raw material for chain transfer agents in the synthesis of block copolymers. Background technique [0002] As an important raw material for the synthesis of dithioester chain transfer agents - dithiobenzoic acid, because of the huge demand in RAFT polymerization (reversible addition-fragmentation chain transfer polymerization), there have been many synthetic dithiobenzoic acids in recent years. Methods, including: aromatic methane monohalogenation method (Bai, R.K., You, y.z., Pan, e.Y.. 60 Co, γ-Irradiation-Initiated "Living" Free-Radical Polymerization in the Presence of Dibenzyl Trithiocarbonate [J] Macromol. Rapid. Commun, 2001, 22: 315-319.), Grignard reagent method (You, Y.Z., Bai, R.K. , Pan, C.Y..A Novel to Triblock Coplyumers: 60 Coγ-Irradiati...

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Problems solved by technology

Wherein the Grignard reagent method and the aromatic aldehyde method though the yield of the product dithiobenzoic acid are all higher, but because the Grignard reagent method is harsh to the reaction conditions, one of the raw materials used in the aromatic aldehyde method, sodium hydride, has a high chemical reactivity. It can spontaneously ignite in the air, and the operation is dangerous. Therefore, it is unlikely to use these two methods in areas with poor synthesis equipment and high ambient humidity.

Although the aromatic methane monohalogenation method has the advantages of simple raw materials used and easy control of the synthesis process, it occupies an important position in the method of synthesizing dithiobenzoic acid, but there are still some problems in the synthesis of this method that has been reported now: the one is The actual synthetic yield is not high

The main reasons for this problem are: firstly, because the sublimated sulfur is not fully dispersed and some of the sublimated sulfur has a side reaction with oxygen before the reaction, so that 45% of the sublimated sulfur does not participate in the main reaction; secondly, the process flow of the synthesis process is too complicated, It takes about 30 hours to complete the operation continuously, and the efficiency is low; third, because the by-products are not easy to remove, multiple purifications are required, which not only brings complicated operations, but also requires the use of a large amount of volatile organic solvents for purification, which will cause great waste and pollute the environment

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