Preparation and hydrogen bonding studies of phenylhydrazone derivatives of alloxan: crystal and molecular structure of pyrimidine-2(1H),4(3H),5,6-tetraone 5-(2-nitrophenyl)hydrazone

Abstract

Eight phenylhydrazone derivatives of pyrimidine-2(1H),4(3H),5,6-tetraone, or 5-oxobarbituric acid (alloxan), are described. Spectroscopic pyrimidine (¹H n.m.r., i.r.) data indicate the presence of extensive hydrogen bonding which, as shown by X-ray crystallographic data for the title hydrazone, includes both intra- and inter-molecular interactions. The title hydrazone, C₁₀H₇N₅O₅, is monoclinic, space group P2₁/a, a= 9.104(8), b= 17.975(13), c= 10.333(8)Å, β= 113.5(1)°, Z= 4.2145 Independent reflections have been measureed on a diffractometer and the structure has been determined by direct methods and refined to R 0.074. There are four independent hydrogen bonds in the asymmetric unit: two intramolecular bonds which link N(7)–H(7) to an o-NO₂ group of the benzene ring and to a carbonyl group of the barbiturate ring and two intermolecular bonds which link NH sites of the barbiturate ring to a solvent NN-dimethylformamide oxygen atom and to a carbonyl oxygen atom of another barbiturate ring across a centre of symmetry.