Clinical Analysis of Urea Nitrogen. Chemical Structure of the Colored Reaction Product of Urea with Diacetylmonoxime and Thiosemicarbazide

Abstract

The chemical structure of the color reaction product, 2-amino-5, 6-dimethyldihydro-3H-1, 2, 4-triazine-3-one (3a), obtained from the reaction of urea with diacetylmonoxime (DAM) and thiosemicarbazide (TSC) in 10% sulfuric acid in methanol was elucidated. The ethyl and p-tolyl derivatives (3b and 3c) of 3a were also obtained from the reactions of ethyl- and p-tolylurea with DAM and TSC, along with 1, 1'-disubstituted-5, 4'-dimethly-2, 2'-dioxo-4, 5'-diimidazolylmethanes. 3a and its derivatives, 3b and 3c, develop a red color immediately in acidic media and are thought to be the main products of the color reaction of urea, ethylurea and p-tolylurea, respectively, with DAM in the presence of TSC. A reaction mechanism is proposed.