ISSN:
0377-0486
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Calorimetric (DTA), infrared, Raman and inelastic neutron scattering (INS) measurements have been performed for the trimethyloxosulphonium iodide compounds (CH3)3SOI and (CD3)SOI over the range 10-450 K. Two solid-solid phase transitions were found at about 200 and 250 K and the vibrational study showed that only the low-temperature crystalline form (III) is completely ordered. From a temperature dependence study of the optical and INS spectra it is concluded that methyl group reorintations are mainly involved in the phase (III)↔phase (II) transition, while the whole molecule reorientations about the three-fold axis, partly involved in the phase (II)↔phase (I) transformation, must be much slower than and decoupled from methyl motions. Finally, the potential barrier height against methyl rotations has been estimated to 13.3 kJ mol-1 from the observed torsional frequencies and compares favourably with the activation energies derived from previous NMR experiments (10.9 kJ mol-1) and from quasi-elastic neutron scattering results (10.6 kJ mol-1).
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jrs.1250160109
