Structures of N-(arenecarbonyl)-N,N′-dicyclohexylureas, cyclohexyl-NH—C(O)—N(cyclohexyl)—C(O)Ar, (Ar = Ph, pyridin-3-yl and pyrazinyl)

Abstract

Abstract The crystal structures of three N-(arenecarbonyl)-N,N′-dicyclohexylureas, [1: ArCO-N(cyclohexyl)-CO-NH-cyclohexyl: (R = Ph (1a), pyridin-3-yl (1c) and pyrazinyl (1e)] are reported from data collected at 120K. Comparison of the new findings with published data for the three compounds indicates three forms have been recognized for this group of compounds: an orthorhombic-form [P212121] and two triclinic [P-1] forms – triclinic-I and triclinic-II. Orthorhombic and triclinic-II phases have been determined for compound, 1a, triclinic-I and triclinic-II forms for compound 1c, and just the orthorhombic form for compound, 1e. Orthorhombic 1a and 1e are isostructural, as are triclinic-II 1a and 1c. The asymmetric unit for the orthorhombic form contains just a single molecule, while the molecules are linked into chains, C(7)R2 2(11), via strong N—H ··· O and weaker C—H ··· O intermolecular hydrogen bonds. The asymmetric unit for triclinic-I consists of two independent molecules, molecules A and B, which are linked alternatively into chains, C(8)R2 2(16), via N—H ··· N and C—H ··· O intermolecular hydrogen bonds in the direction of the a axis: such chains are linked via C—H ··· O hydrogen bonds. The asymmetric unit of the triclinic-II phase also comprises two independent molecules, molecules A and B, which are also linked alternatively into chains, C(8), but only via N—H ··· O hydrogen bonds, with other intermolecular interactions of the C—H ··· π type also present.