alpha-iminohydroxylamine-alpha-aminonitrone tautomerism: A 1:1 mixture of two tautomeric forms in crystals of N-(4,5-dihydro-1H-imidazol-2-yl)-N-phenyl-hydroxylamine

Crystals consisting of two distinct chemical entities, tautomers of each other, in exact 1:1 ratio, have been obtained and their structure determined by X-ray analysis. The crystals of C9H11N3 . C9H11N3 are monoclinic, P2(1)/c, a = 15.674(3), b = 17.085(3), c = 13.758(3)Angstrom, beta = 90.78(2)degrees, Z = 8. There are two hydroxylamine and two aminonitrone molecules in the asymmetric unit. Hydrogen bonds connect those molecules into chiral layers. Layers of opposite chirality alternate and the crystal is centrosymmetric as a whole, Within those layers chains of tautomers joined by very strong O-H ... O and strong N-H ... N bonds can be recognized. Proton transfer along those chains with simultaneous rearrangement of pi-bonds within the molecules would result in interconversion of tautomers and would affect: chirality of the layer.