Preparation method of methomyl oxime

Abstract

The invention discloses a preparation method for methomyl oxime. The preparation method comprises the following steps: (1) respectively dissolving acetaldehyde oxime and chlorine gas in an organic solvent to obtain an organic solution of acetaldehyde oxime and an organic solution of chlorine gas, and dissolving sodium methyl mercaptide and sodium hydroxide in an organic solvent to obtain a mixed organic solution; (2) with the organic solution of acetaldehyde oxime and the organic solution of chlorine gas as raw materials, carrying out continuous feeding for a chlorination reaction; and (3) immediately subjecting a chlorinated mixed solution obtained by a chlorination reaction to a methylthio substitution reaction with the mixed organic solution, removing the solvent from a crude methomyl oxime product obtained by the reaction, and adding a small amount of water to wash the crude methomyl oxime product so as to obtain high-quality methomyl oxime. The method is controllable in reaction heat, small in by-product influence, short in time, capable of avoiding decomposition of chloroacetaldoxime, low in the amount of generated wastewater and free of wasterwater odor, and the obtained finished methomyl oxime is high in yield and quality.

Description

technical field [0001] The invention belongs to the technical field of preparation of fine chemical intermediates, in particular to a preparation method of methomyl oxime. Background technique [0002] Methomyl is an oxime carbamate insecticide. It was first recommended by DuPont of the United States as an insecticide and nematicide in 1966. Its active ingredient is 1-(methylthio)ethylene-methyl carbamate. It is a systemic broad-spectrum, high-efficiency, fast, and low-residual toxicity ovicide and insecticide. It kills pests and eggs through contact and stomach poisoning. It has strong lethality, quick effect, wide insecticidal spectrum, and low residual Low, suitable for a wide range of crops, safe to use, widely used in more than 30 crops such as cotton, cabbage, tobacco, citrus, soybeans, and peanuts. [0003] Methomyl oxime is the main intermediate for the synthesis of methomyl, and its structural formula is as follows: [0004] [0005] There are five main synthe...

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Problems solved by technology

[0006] U.S. Patents US 3987096, US 3752841, US4327033, etc. all provide the synthetic method for preparing methomyl oxime by the acetaldehyde oxime method, but all have the following disadvantages: the reaction adopts "one-pot method", and when chlorine gas is passed into the reaction system for reaction, the Accumulation of by-products, unstable reaction temperature, difficult control and excessive addition of raw materials, difficult control of reaction heat, large influence of by-products, long reaction time, and easy decomposition of chloroacetaldoxime

Chinese patent CN109627183A provides a synthetic method for preparing chloroacetaldehyde oxime by acetaldehyde oxime method, but there are disadvantages such as that the reaction is difficult to be accurately controlled, resulting in many impurities, the heat and reaction heat temperature are still difficult to control, and the product is easy to decompose. The presence of water will cause the system to be strongly acidic and accelerate the decomposition of chloroacetaldoxime

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