7,9-Bis(hy­droxy­meth­yl)-7H-purine-2,6,8(1H,3H,9H)trione

The structure of the title uric acid derivative, C7H8N4O5, from human kidney stones, is characterized by the C and O atoms of one of the two hy­droxy­methyl groups being disordered nearly equally over three different sites. In the crystal, mol­ecules are connected by a three-dimensional hydrogen-bonding scheme though they look stacked in planes nearly parallel to (04)

Melamine/epichlorohydrin prepolymers: syntheses and characterization

The basic catalysis of melamine with epichlorohydrin gives prepolymers that can be used in the preparation of energetic materials. In this work, sodium hydroxide and triethylamine were used as catalysts and ethyleneglycol as initiator. Different reaction conditions were tested and the characterization of the products was carried out by IR and NMR spectroscopy and MS spectrometry, hydroxyl groups content, vapour pressure osmometry and elemental and thermal analysis. Epichlorohydrin reacts with the amine groups of melamine and forms lateral chains with hydroxyl and epoxide end groups, which can be used for curing purposes. The two catalysts lead to similar products, confirmed both by the structure and number of the lateral chains. The melamine/epichlorohydrin ratio was found important for the structure of the final compounds. Chlorine atoms leave the molecules during reaction due to basic catalysis. In the light of the use of the prepolymers in energetic materials, the presence of the 1,3,5-s-triazine ring and the lateral chains with end groups curable by e.g. isocyanates was accomplished with success. However, the loss of chlorine atoms limits to a certain extent their possible substitution by energetic groups.http://www.sciencedirect.com/science/article/B6TXW-4F9247B-5/1/7bee9df489c5d6ca2f506eeeb1d5708

Cyanuric acid-epichlorohydrin prepolymers

In this study, we investigated the reaction of cyanuric acid and epichlorohydrin (ECH). SnCl4 was used as a catalyst. Several reaction conditions were tested, and the products were analyzed by means of Fourier transform infrared and 1H-NMR spectroscopy, hydroxyl group content, molar mass, elemental and thermal analysis, viscosity, and density. ECH reacted with the amine groups of the cyanuric acid ring to form lateral chains that contained chloroalkyl and hydroxyl end groups. Full substitution of the amine groups was observed in all of the synthesized products. The solvent used in the synthesis was found to be very important for the structure of the final prepolymers. When N,N-dimethylformamide was used, relatively low-molar-mass prepolymers of cyanuric acid and ECH were obtained. When solvents with low dielectric constants were used, no reaction with cyanuric acid was observed. The prepared prepolymers were thermally stable up to 160°C. At this temperature, degradation started via the lateral chains. The viscosity of the products decreased as the ECH-cyanuric acid ratio increased, whereas the density remained basically constant. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3684-3691, 200