Synthesis of Glyoxylic Acid by Glyoxal Oxidation in the Presence of Hydrohalic Acids
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NIC SYNTHESIS AND INDUSTRIAL ORGANIC CHEMISTRY
Synthesis of Glyoxylic Acid by Glyoxal Oxidation in the Presence of Hydrohalic Acids M. A. Pozdniakova, I. V. Zhuk a, A. S. Salikova, V. V. Botvina,*, and A. G. Filimoshkina a
National Research Tomsk State University, Tomsk, 634050 Russia *e-mail: [email protected]
Received August 28, 2019; revised August 3, 2020; accepted August 10, 2020
Abstract—A procedure was developed for preparing glyoxylic acid by glyoxal oxidation with nitric acid in the presence of hydrohalic acids with selective isolation of glyoxylic acid from the reaction mixture in the form of magnesium and calcium salts. Specific features of the synthesis of glyoxylic acid were demonstrated, and optimum conditions for each step of the process were determined. The highest yield of glyoxylic acid was obtained in oxidation of glyoxal with an HNO3 : HCl mixture. Oxidation in the presence of HF and HBr is characterized by lower yields because of low dissociation constant of HF and side redox reactions with HBr. Dilute solutions of glyoxylic acid were obtained by an exchange reaction of its calcium salt with a hydrofluoric acid solution at room temperature. An increase in the reaction temperature leads to an increase in the content of glycolic and oxalic acids formed by disproportionation of glyoxylic acid in the initial step of the exchange reaction. Keywords: glyoxal oxidation, glyoxylic acid, oxalic acid, alkaline earth metal salts DOI: 10.1134/S107042722010122
Glyoxylic acid is one of the most important aldehydo acids containing aldehyde and carboxyl groups simultaneously. Owing to the bifunctional structure, this compound finds wide use and is of much interest both for basic research and for various branches of industry. Glyoxylic acid is used in production of drugs (Meticillin, Allantoin, Atenolol), of vanillin for perfume and food industry and for pharmaceutics, and of glyphosate for agricultural chemistry [1]. Glyoxylic acid is produced using as starting chemicals various organic compounds: glyoxal, maleic, glycolic, oxalic, dichloroacetic, and tartaric acids, ethylene glycol, and ethanol, and also silver dihaloacetates [1]. The procedure for producing glyoxylic acid by oxidation of aqueous glyoxal solutions with concentrated nitric acid in the presence of hydrochloric acid is of commercial interest [2]. The process ensures relatively high yields of glyoxylic acid, about 75–90%; however, there are no data on specific features of similar processes performed in the presence of other hydrohalic acids: hydrofluoric and hydrobromic. Another complex problem is the product separation and selective isolation of glyoxylic acid. The process is
complicated by simultaneous presence of starting reactants, auxiliary reagents, target product, and byproducts, often exhibiting similar chemical properties, in the aqueous solution of glyoxal oxidation products [3]. Along with the residual unchanged glyoxal and nitric acid, oxalic acid is the major oxidation by-product in the reaction mixture. Thus, separation of a mixtu
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