The crystal structures of m-xylene and p-xylene, C8D10, at 4.5 K

The crystal structures of perdeuterated m-xylene, space group Pbca, a = 10. 1550(1), b = 7.4649(1), c = 16.8814(1) Angstrom, V = 1279.72(2) Angstrom(3) , Z = 8, rho(calc) = 1.1021(1) g cm(-3) and perdeuterated p-xylene, space g roup P2(1)/n, a = 5.7337(1), b = 4.9485(1), c = 11.1385(1) Angstrom, beta = 100.7130(1)degrees, V = 310.52(2) Angstrom(3), Z = 2, rho(calc) = 1.2431(1 )g cm(-3) at 4.5 K have been refined against high-resolution neutron powder diffraction data. The previously unknown structure of m-xylene was solved from the neutron powder diffraction data utilising a simulated annealing me thod and verified by a conventional Direct Methods solution using X-ray sin gle crystal data. The inter-molecular contacts determined in the structures of the meta and para compounds are closely related. (C) 2000 Elsevier Scie nce B.V. All rights reserved.