The crystal structure of imidazole at –150°C

Abstract

783 tion, it now has all real amplitudes. The B values, amplitudes , and direction cosines of the principal axes are (in the order B, amplitude, ~0, ~, co): 3.42 A 2, 0.208 A,-0.316,-0.685, 0.706; 2.62 A 2, 0.182 A, 0.945,-0.165, 0.094; 1.55 A 2, 0.140 A,-0.085, 0.711, 0.702. Imidazole, C3N2H4, crystallizes in the space group P21/c. There are four molecules in the cell, the dimensions of which are, at-150°C: a= 7-582, b = 5.371, c= 9.790 A; B= 61 ° 1'. The five-membered ring is planar. All bond lengths in the ring indicate considerable double-bond character. NH • • • N bonds with the exceptionally short length of 2.86 A form chains of molecules along the c axis.