"Proton spin-lattice relaxation and methyl group rotation" by Peter A. Beckmann, C. I. Ratcliffe et al.
 

Document Type

Article

Version

Author's Final Manuscript

Publication Title

Journal of Magnetic Resonance

Volume

32

Publication Date

1978

Abstract

Proton spin-lattice relaxation times have been measured at 16, 31, and 59 MHz in 4-methyl-2,6-ditertiarybutyl phenol between 80 K and its melting point, 340 K. The variation of T1 with temperature shows too distinct minima. The lower-temperature minimum has been analyzed in terms of relaxation by reorientation of four of the six t-butyl methyl groups with an average apparent activation energy of about 2.4 kcal mole−1 (104 meV molecule−1). The higher-temperature minimum has been analyzed in terms of relaxation by reorientation of the t-butyl groups about their C3 axes with four of the six t-butyl methyl groups reorienting very rapidly, and the remaining two reorienting with correlation time similar to that of the t-butyl group. The activation energy for the higher-temperature minimum is 5.76 kcal mole−1 (250 meV molecule−1). Steric potential calculations are used to add weight to these assignments, and a number of peculiarities displayed by the lower-temperature minimum are discussed.

DOI

https://doi.org/10.1016/0022-2364(78)90054-9

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