Formation of Guanidinium Salts by the Reaction of Urea with Triammonium Nitridotris(sulfate) under an Atmospheric Pressure

Abstract

The effect of ammonia on the formation of guanidinium ion (GH⁺) by the reaction of urea with triammonium nitridotris (sulfate) (TNS) in the molten state under an atmospheric pres sure, has been studied.
The bubbling of ammonia into the melt during the reaction of urea with TNS (molar ratio 1: 2/3) suppressed side reactions, gave fluidity to the melt, and led to a considerable increase of GH⁺ yield. These results, including the IR spectra of reaction mixtures, the yields of GH+ and by-products vs. reaction temperature, were analogous to those from the reaction of urea with diammonium imidobis (sulfate) (DIS) (molar ratio 1: 1) with the bubbling of am monia. Furthermore, TNS was readily ammonolyzed to ammonium amidosulfate (AAS) and DIS in the presence of urea at the temperature as low as 160°C. Based on these results, the formation path of GH⁺ in the reaction of urea with TNS with the bubbling of ammonia was considered to be substantially the same as that in the reaction of urea with AAS or DIS with the bubbling of ammonia. In these reactions, TNS, DIS and AAS may be taken as equivalent to one another at the molar ratio of 2: 3: 6,