Temperature dependence and tunneling frequency measurement of methyl group in some Tert-Butyl series

ABSTRACT The temperature dependence of nuclear (proton) spins lattice relaxation time, T1. The tunnel splitting and the hopping rate depend upon the height and the shape of the hindering barrier to the methyl rotation and carry information on the group’s molecular environment are reported for a number of samples containing tertiary-butyl groups.The temperature rang was 4k to 300k. This data has been analyzed to provide estimates for the magnitudes of the three-fold potential barrier to reorientation of all methyl groups in these materials. At low temperature the motion of the tertiarybutyl protons can usually be neglected- cross relaxation due to the dipolar interaction, is much more rapid that spinlattice relaxation. All protons of the sample relax as a single system.In one or two cases tunneling is observed for the first time in tert-butyl. The T1 results are used to evaluate tunnel frequencies in other cases. The results suggest the importance of collective motion of methyl groups in tert-butyl.