Cyclohexanone at 150 K

Abstract

The structure of cyclo­hexa­none, C6H10O, at 150 K is that of discrete mol­ecules, with no strong intermolecular interactions.

The low-temperature phase III structure and phase transition behaviour of cyclohexanone

“…The advent of techniques for the in situ growth of single crystals from liquids (see, for example, Boese & Nussbaumer, 1994;Boese et al, 2003;Pardoe et al, 2003) can provide a route for structural studies that bypass the potentially destructive first-order transition. Shallard-Brown et al (2005) successfully grew a single crystal of cyclohexanone at 180 K by careful zone melting and reported an ordered orthorhombic structure in the space group P2 1 2 1 2 1 at 150 K. Analysis of the low-frequency Raman spectrum (Huang et al, 1993) suggests an orthorhombic noncentrosymmetric structure for phase III at 73 K, which is apparently in agreement with the single-crystal observations. The spectroscopic observations, however, may have been potentially misleading as the previously reported orthorhombic structure is shown here to correspond to phase II.…”

“…These invariably reproduced the monoclinic phase, however, additional peaks from a minor second phase were observed. This second phase could be indexed using an orthorhombic cell [150 K: a = 5.3677 (4), b = 7.0295 (4), c = 15.147 (1) Å , V = 571.54 Å 3 ] in agreement with the structure of Shallard-Brown et al (2005) who report a cell volume of 574.63 Å 3 at the same temperature. A subsequent two-phase refinement of these data showed the weight fraction of the orthorhombic phase to be only 0.053 (1) in the sample.…”

“…The structure also exhibits a COÁ Á ÁCO contact distance of 3.43 Å in an antiparallel motif and is referred to as Type II by Allen et al (1998). Shallard-Brown et al (2005) report no strong intermolecular interactions in the phase II structure, however, there is a 2.61 Å contact in the structure between H62 and O7 which runs along the 2 1 axis along the crystallographic a axis. Type I COÁ Á ÁCO contacts (Allen et al, 1998) of 3.35 Å , characterized by a perpendicular motif, are also evident in the structure and this shorter contact distance may well reflect the lack of competing CHÁ Á ÁO contacts in the phase II structure.…”

6,6′-Dimethoxygossypol: molecular structure, crystal polymorphism, and solvate formation

“…These rings have CremerPople puckering parameters (q = 0.524 Å , h = 9.4°, / = 161°for the major part; q = 0.527 Å , h = 6.3°, / = 136°for the minor part) that are close to those of an ideal chair (i.e., h = 0°). The puckering parameters of both rings are similar to the puckering parameters for crystalline cyclohexanone (q = 0.536 Å , h = 8.2°, / = 170°) [19].…”

“…The cyclohexanone molecule in S2 was also found to be disordered. As the solid-state conformation of cyclohexanone is a ''chair'' form [19], this molecule was modeled in two essentially ''inverted'' chair conformations, and the methylene hydrogen atoms were placed at calculated positions to improve their geometries. DELU and SIMU restraints were also used for some structures to improve their thermal motion parameters [18].…”