Molecular and crystal structure of hexamethylenetetramine oxide

Abstract

The crystal and molecular structure of hexamethylenetetramine oxide, (CH₂)₆N₄O, has been determined by X-ray analysis and the structure refined by full-matrix anisotropic least squares to R 0.053 for 228 diffractometer data. Crystals are trigonal, space group R3m, with Z= 3 in a hexagonal unit cell of dimensions: a= 9.464(1) and c= 6.789(1)Å. The cage molecule retains its idealized 3m symmetry in the crystal. The N→O dative bond of 1.363(6)Å is the shortest formal single bond between nitrogen and oxygen yet reported. The three sets of C–N bonds disposed successively further away from the polar N-oxide function vary in the order long, short, and normal, relative to the C–N bond in hexamethylenetetramine. Values of C–N–C angles at tertiary and quaternary nitrogen atoms suggest that the formally negative exocyclic oxygen atom is comparable to a lone pair in regard to stereo-chemical significance.