The reorientation oft‐butyl groups in butylated hydroxytoluene: A deuterium nuclear magnetic resonance spectral and relaxation time study
| Autor: | J. D. Dean Fyfe, James M. Polson, Kenneth R. Jeffrey |
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| Rok vydání: | 1991 |
| Předmět: | |
| Zdroj: | The Journal of Chemical Physics. 94:3381-3388 |
| ISSN: | 1089-7690 0021-9606 |
| DOI: | 10.1063/1.459761 |
| Popis: | Deuterium nuclear magnetic resonance (NMR) spectra and spin–lattice relaxation times were determined in order to study the dynamics of t‐butyl groups in butylated hydroxytoluene. The results are consistent with a model first proposed by Beckmann et al. [J. Magn. Reson. 36, 199 (1979)], where there is an inequivalence between the methyl groups within each t‐butyl group. While two methyl groups reorient rapidly relative to the whole t‐butyl rotation, the remaining methyl group is more restricted in its motion, reorienting at a rate comparable to that of the t‐butyl group itself. The spin–lattice relaxation data show two T1 minima, the high temperature minimum (40 °C) corresponding to the combined t‐butyl and ‘‘slow’’ methyl rotations, and the low temperature minimum corresponding to ‘‘fast’’ methyl group rotation. Using an explicitly defined T1 fitting function, the T1 data yield activation energies of 2.2 and 6.0 kcal/mol for the fast methyl and t‐butyl rotations, respectively, both in agreement with Beckm... |
| Databáze: | OpenAIRE |
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