Singularities in Molecular Conformation

Abstract

The intramolecular coupling between molecular groups leads to singularities in the molecular conformation, acting like a switch in a molecular-scale rotor. This, in turn, affects the potentialenergy (E p ) barriers, acquiring a sharp shape originating from superimposed E p functions of the molecular conformers with differently coupled methyl groups. The molecular conformation fixed at the switching position results in the disordered methyl orientations in the crystalline state.These general features have been observed for the molecule of pinacolone. The structure of the pinacolone crystals frozen at low-temperature isobaric and high-pressure isochoric conditions have been determined.Introduction.

Direct and Inverse Relations between Temperature and Pressure Effects in Crystals: A Case Study on o-Xylene

“…The liquid-sample regions of isothermal compression at 296 K and isobaric cooling at 0.1 MPa are highlited in blue and scaled to the same width. 44 The crystallization pressure at 296 K is indicated by p c . situ crystallized samples indicate that the compression of a is negative to about 0.5 GPa.…”

“…Herring-bone schemes of molecular aggregation exaggerate its changes upon heating and compression in the insets (bottom). The liquid-sample regions of isothermal compression at 296 K and isobaric cooling at 0.1 MPa are highlited in blue and scaled to the same width 44. The crystallization pressure at 296 K is indicated by p c .…”