Crystal and molecular structure of the 1 : 1 complex of urea and syn-5-nitro-2-furaldehyde oxime

Abstract

The crystal structure of the title adduct has been determined by X-ray diffraction techniques. The crystals are monoclinic, space group P2₁/c, Z= 4, with unit-cell dimensions a= 6·571 (2), b= 17·575(7), c= 8·472(3)Å, and β= 104·47(3)°. The structure was determined by using a combination of symbolic addition and Patterson methods and was refined by full-matrix least-squares methods to R 0·053 for 1215 observed reflections. The structure consists of hydrogen-bonded layers of nearly planar syn-5-nitro-2-furaldehyde oxime molecules and urea molecules. The distances in the furan ring together with the short C–N (nitro) distance suggest an interaction between the nitro-group and the ring. The absence of a urea adduct of the anti-isomer is discussed.