The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 07, 1978
Filed:
Mar. 09, 1977
Giuseppe Ribaldone, Gallarate (Varese), IT;
Renato Grecu, Cameri (Novara), IT;
Montedison S.p.A., Milan, IT;
Abstract
Process for the preparation of the monopotassium salt of 1,2,5-thiadiazol-3,4-dicarboxylic acid (I). Involves double-stage saponification of 3,4-dicyano-1,2,5-thiadiazole (II), 3-cyano-4-carbamoyl-1,2,5-thiadiazole (III) is obtained from an aqueous suspension of 3,4-dicyano-1,2,5-thiadiazole (II) by catalytic hydration through the addition of aqueous KOH, desirably at a temperature of from 20.degree. to 50.degree. C. and with a molar ratio of 3,4-dicyano-1,25-thiadiazole (II) to KOH of from 1:0.01 to 1:0.8. This is followed by hydrolysis, by the further addition of aqueous KOH, desirably at a temperature of from 85.degree. to 100.degree. C., until attaining an overall molar ratio of 3,4-dicyano-1,2,5-thiadiazole (II) to KOH of from about 1:2.0 to 1:2.35, a molar ratio of 3,4-dicyano-1,2,5-thiadiazole (II) to H.sub.2 O of from about 1:20 to 1:23. Thereafter, from the resulting solution of dipotassium salt of 1,2,5-thiadiazole-3,4-diccarboxylic acid, the monopotassium salt is separated by acidification of said solution.