Process for preparing DL-ortho-chloro mandelic acid

Abstract

The process of preparing DL-ortho-chloro mandelic acid includes the following steps: 1. the cyanidation reaction of o-chloro benzaldehyde and hydrocyanic acid in the molar ratio of 1 to 0.9-1.5 to produce o-chloro mandelonitrile at the temperature of -20 to +20 deg.c and in the presence of alkaline catalyst; 2. hydrolyzing the product via adding inorganic acid and heating to 20-120 deg.c; 3. eliminate ammonium chloride through adding toluene into the hydrolysate, heating for azeotropic dehydration to separate out ammonium chloride and filtering out ammonium chloride; and cooling the filtrate to crystallize and filtering to obtain crude DL-ortho-chloro mandelic acid product; and 4. refining crude DL-ortho-chloro mandelic acid product through dissolving in toluene and re-crystallizing to obtain qualified DL-ortho-chloro mandelic acid product. The present invention has lowered production cost and high yield.

Description

Technical field:

[0001] The present invention is related to the preparation method of DL-o-chloromandelic acid. Background technique:

[0002] The existing methods for preparing DL-o-chloromandelic acid mainly include the following two methods.

[0003] 1. O-chlorobenzaldehyde phase transfer catalytic method:

[0004] In this method, o-chlorobenzaldehyde is mixed with bromoform or chloroform under alkaline conditions, and reacted in the next step under the action of a phase transfer catalyst to obtain DL-o-chloromandelic acid. product. The reaction yield of this method is low, and the production cost is high.

[0005] 2. O-chlorobenzaldehyde cyanation method:

[0006] The method for preparing DL-o-chloromandelic acid with hydrocyanic acid as a cyanating agent has been reported in the document "Journal of the American Chemical Society" (J Am Chem.Soc) S.S.Jenking 1931.53.3241. Water hydrocyanic acid reacts to generate o-chloromandelonitrile, and o-chloromandelonitrile is...

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