FIELD: chemistry.
SUBSTANCE: invention relates to production of metal carboxylates. In particular, the invention relates to production of a new crystalline form of cis-2,3-epoxy succinate calcium (salts of 2,3-epoxy-1,4-butanedioic acid) and is a raw material for obtaining L - (+) - tartaric acid. Method of producing the crystalline modification of cis-2,3-epoxy succinate calcium involves the following steps: a) partial neutralization of maleic acid or maleic anhydride with a first portion of a calcium compound to obtain acidic calcium maleate; b) epoxidation of acidic calcium maleate with hydrogen peroxide in the presence of epoxidation catalysts to obtain acid cis-2,3-epoxy succinate calcium; c) neutralizing the acid cis-2,3-epoxy succinate calcium by adding a second portion of the calcium compound; d) holding cis-2,3-epoxy succinate calcium for 24 to 240 hours to obtain a crystalline form of cis-2,3-epoxy succinate calcium, where the crystals belong to the space group P21/n, wherein the crystal lattice parameters at 22 °C are a= 15.1916 (2) Å, b = 8.9121 (1) Å, c = 7.4724 (1) Å, beta = 103.309 (1)°, where step (b) epoxidation is carried out at a pH value not higher than 3.
EFFECT: technical result is obtaining a crystalline form of cis-2,3-epoxy succinate calcium with content of D-tartaric acid (by-product) of 1.2 % and less, with pH of epoxidation stage not higher than 3.
75 cl, 4 tbl, 5 dwg
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