relation: http://publicatio.bibl.u-szeged.hu/32477/
title: Phase dependence of conformational motions in solids. The tert-butyl rotation in (1R*,2S*,5R*)-5-tert-butyl-2-hydroxycyclopentanecarboxylic acid
creator:  Riddell Frank G.
creator:  Bernáth Gábor
creator:  Fülöp Ferenc
subject: 01.04. Kémiai tudományok
subject: 01.06. Biológiai tudományok
subject: 03.01. Általános orvostudomány
description: (1R(*),2S(*),5R(*))-5-tert-Butyl-2-hydroxycyclopentanecarboxylic acid exists in several solid phases, two of which are investigated in this report: a first phase (phase I) obtained by crystallization from common solvents and a second phase (phase II) obtained by heating the first phase above ca. 70 degrees C. The second phase appears to be the stable phase at ambient temperature, and the first phase appears to be a metastable phase. A third phase (phase III), which reverts to phase II on standing at room temperature, is obtained by cooling the melt to room temperature. The rates of rotation of the tert-butyl groups in phases I and II have been measured by CP/MAS NMR techniques. The activation parameters for the tert-butyl group rotation differ markedly between the two phases: phase I, Delta H not equal = 59.0 +/- 2.1 kJ mol(-1), Delta S not equal = 51.6 +/- 8.1 J K-1 mol(-1); and phase II, Delta H not equal = 43.9 +/- 2.5 kJ mol(-1), Delta S not equal = 28.3 +/- 9.3 J K-1 mol(-1). The structure of phase I has been solved by X-ray diffraction techniques, and this assists in understanding the experimental observations.
date: 1995
type: Folyóiratcikk
type: PeerReviewed
format: text
identifier: http://publicatio.bibl.u-szeged.hu/32477/1/aok_klny_180_95.pdf
identifier:     Riddell Frank G.;  Bernáth Gábor;  Fülöp Ferenc: Phase dependence of conformational motions in solids. The tert-butyl rotation in (1R*,2S*,5R*)-5-tert-butyl-2-hydroxycyclopentanecarboxylic acid.   JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 117 (8).  pp. 2327-2335.  ISSN 0002-7863 (1995)     
identifier: doi:10.1021/ja00113a022
relation: https://doi.org/10.1021/ja00113a022
relation: 27998
language: eng