Plastic phases in globular phosphorus compounds. A new structural criterion for plastic behavior

Abstract

Somewhat similar values would be found for = 4 if the low temperature results were given more weight than high temperature ones.Fletcher and Heller7 reported for the cyclization of the 1-octanol tetramer is n-decane AH°c = -3.8 kcal/mol and AS°c = -11.2 cal/deg mol. The agreement between the two sets of data is within the experimental uncertainty. ConclusionsThe results obtained in this study confirm the assignment made in our previous works, namely, that the excess ultrasonic absorption of alcohol solutions in cyclohexane is due to the formation of noncyclic tetramers or pentamers. The values of the activation enthalpy and entropy for the association of one alcohol molecule to an (nl)-mer confirm that this reaction is diffusion controlled. The activation enthalpy and entropy for the dissociation of an alcohol molecule from the stable noncyclic n-mer have been obtained for the first time. These two quantities are positive. The equilibrium thermodynamic quantities for the formation of noncyclic and cyclic species have also been obtained. They are in agreement with those determined by "equilibrium" measurements.Supplementary Material Available: Tables of raw ultrasonic absorption data (3 pages). Ordering information is given on any current masthead page.

Thermodynamic Consideration on a Series of Compounds (CH3)nCCl4-n: Correlation between Molecular Sphericity, Configurational Order/Disorder, and Molecular Packing in Plastically Crystalline and Liquid Phases

“…The thermodynamic properties have been studied so far for many compounds showing plastically crystalline phase. , To elucidate the detailed state of aggregation of the molecules, then it is attractive to examine the dependence of some physical quantities on the deviation of molecular shape from the sphere. Nakamura et al in fact examined the relation between the molecular shape and some thermodynamic quantities and pointed out that nonsphericity of the constituent molecules operates to diminish the value of the fusion entropy and to narrow the temperature range of the plastically crystalline phase.…”

Cubic Mesophase in an Unsymmetrical Alkyl Ammonium Salt. Synthesis and Structural Model

“…According to literature data,11 this value can be related to a first‐order transition between a disordered mesophase and the isotropic liquid. The arrangement of orientationally disordered molecules into a cubic lattice is the common feature of plastic crystals 12, 13. Below room temperature, the thermogram reveals a glass phase transition at −59 °C (50.7 J K −1 mol −1 ), confirming that conformational disorder and motion coexist with periodicity in the crystalline mesophase.…”

Rotational Phase Transition and Melting in a Two-Dimensional Hard-Cyclic-Tetramer System

“…There is no doubt that molecular shape plays a crucial role in the existence of these phases. 4,5 The problem is complicated mathematically and it seems reasonable to study first two-dimensional (2D) systems.…”

“…These satellite faces could be interpreted 2 by extension of the classical geometrical theories of Bravais, 3 Friedel, 4 and Donnay and Harker. 5 On the basis of the Bravais-Friedel-Donnay-Harker law, a fairly large number of satellite faces is expected to have about the same morphological importance. Their simultaneous appearance is favored by use of spherically shaped single crystals as the initial growth form.…”