Deuterium and carbon-13 NMR of the solid polymorphism of benzenehexoyl hexa-n-hexanoate
Deuterium and carbon-13 NMR of specifically labeled benzenehexoyl hexa-n-hexanoate in the various solid-state phases are reported. The spectra exhibit dynamic line shapes which change discontinuously at the phase transitions. The results are interpreted in terms of sequential melting of the side chains on going from the low-temperature solid phases IV, III, etc., toward the liquid. In phase IV the molecules are very nearly static, except for fast rotation of the methyl groups about their C/sub 3/ axes. The results in phase III were quantitatively interpreted in terms of a two-site isomerization process involving simultaneous rotation by 95/sup 0/ about C/sub 1/-C/sub 2/ and transition from gtg to g'g't (or equivalently g'tg' to ggt) for the rest of the chain. The specific rate of this reaction at 0/sup 0/C is approx. 10/sup 5/s/sup -1/. In phase II additional chain isomerization processes set-in which were, however, not analyzed quantitatively. Further motional modes, involving reorientation of whole chains about their C/sup ar/-O bonds, appear on going to phase I. In all solid phases the benzene ring remains static.
- Research Organization:
- Weizmann Inst. of Science, Rehovot (Israel)
- OSTI ID:
- 5736490
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 109:24
- Country of Publication:
- United States
- Language:
- English
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ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
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NUCLEAR MAGNETIC RESONANCE
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ISOTOPE EFFECTS
DEUTERIUM COMPOUNDS
CARBON 13
EXPERIMENTAL DATA
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SOLIDS
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400202* - Isotope Effects
Isotope Exchange
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