Studies On Synthesis Of Crystal Glyoxylic Acid And Its Main Derivatives

Glyoxylic acid is an important organic chemical intermediate and many fine chemical products can be derived from it. At present, the commercial glyoxylic acid produced by traditional processes is an aqueous solution of 30%~50%. Due to the presence of water, it can not meet the need of medicine, food and other industries for higher purity crystal glyoxylic acid product.In this paper, higher purity crystal glyoxylic acid was prepared using maleic acid as raw material, water as solvent and ozone as oxidant. The obtained optimum reaction conditions were reaction temperature 30℃, reaction time 8h, reactant weight percent 30%, vacuum distillation end temperature 50~60℃at 1.6kPa. Under above conditions, the yield of product was up to 96% with the purity of 97%. The purity of obtained product was measured by ion chromatography and the structure was characterized by FT-IR.Many glyoxylic acid derivatives are high value-added chemical products and can be used in many fields. In this paper, three main derivatives of glyoxylic acid, allantoin, 5-(4-hydroxyphenyl) -hydantoin and DL-4-hydroxyphenylglycine, were synthesed using crystal glyoxylic acid as raw material.The effects of solvent kinds, molar ratio of solvents, catalyst kinds, molar ratio of catalyst, molar ratio of reactants, reaction time, recrystallization dissolution temperature and recrystallization dissolution time on reaction results were examined. The obtained optimum conditions for preparation of allantoin using crystal glyoxylic acid as raw material were n(tetrahydrofuran):n(ethanol)=1:1.5, n(sulfuric acid):n(phosphate acid)=1:1, n(crystal glyoxylic acid):n(urea)=1:4, reaction temperature 70℃, reaction time 4h, recrystallization dissolution temperature 90℃, recrystallization dissolution time 40min and pH=3~6. Under above conditions, the yield of allantoin was 85.4% with the purity of 98.9%. After mother liquid was recycled, the yield was up to 87%. The structure of obtained product was characterized by FT-IR, 1HNMR and 13CNMR.Orthogona1 test was used to study the effects of reactant molar ratio, reaction temperature and amount of catalyst on reaction results. The obtained optimum reaction conditions for preparation of 5-(4-hydroxyphenyl)hydantoin using crystal glyoxylic acid as raw material were n(crystal glyoxylic acid):n(urea):n(phenol)=1:2.5:2.5, the amount of hydrochloric acid 30ml, reaction temperature 80℃. Under above conditions, white 5-(4-Hydroxyphenyl)hydantoin was obtained and the yield of product was up to 82.6% with the purity of 98.5%. Moreover, the effects of weight percent of glyoxylic acid solution and different solvents on reaction results were studied. The results showed that the effect of weight percent of glyoxylic acid solution was little and water was suitable for the reaction due to solvent effect. The structure of obtained product was characterized by FT-IR, 1HNMR and 13CNMR.The effects of catalyst kinds, solvent kinds, raw material molar ratio, reaction temperature, reaction time and molar of catalyst on the reaction results were examined. The obtained optimum reaction conditions for preparation of DL-4-hydroxyphenylglycine using crystal glyoxylic acid as raw material, benzyltriethylammonium chloride as catalyst and water as solvent were n(crystal glyoxylic acid):n(phenol):n(sulfamic acid)=1:1.3:1.3, reaction temperature 70℃, reaction time 8h and molar of catalyst 0.002mol. Under above conditions, the yield of DL-4-hydroxyphenylglycine for single batch was 70.6% with the purity of 98.7%, and the yield was improved up to 76% by recycling the mother liquid. The structure of obtained product was identified by FT-IR.The studies on synthesis of allantoin, 5-(4-hydroxyphenyl)-hydantoin and DL-4-hydroxyphenylglycine using crystal glyoxylic acid as raw material have not been reported in literature so far. The yields and purities of above-mentioned glyoxylic acid derivatives synthesed using crystal glyoxylic acid as raw materials are better than those reported in literature using 30%~50% glyoxylic acid solution as raw materials.