$^{13}$C NMR Relaxation Study of Internal Rotation of Methyl Groups-Spin-Rotational Relaxation of methyl Carbon-13 in 2-bromo-p-xylene, 2,5-dimethylanisole and 2,5-dimethylaniline

$^{13}$C NMR Relaxation Study of Internal Rotation of Methyl Groups-Spin-Rotational Relaxation of methyl Carbon-13 in 2-bromo-p-xylene, 2,5-dimethylanisole and 2,5-dimethylaniline

In this work we have investigated temperature dependence of spin-rotational relaxation rate, $(1/T_1)_{SR}$, of methyl carbon-13's in 2-bromo-p-xylene, 2,5-dimethylaniline, and 2,5-dimethylanisole and have found that temperature behaviors of two methyl carbon-13's in ortho- and meta-position, respectively, are substantially different. It has been confirmed that the modified Burke-Chan model proposed by Park et al. can nicely explain different temperature dependence of $(1/T_1)_{SR}$ for these two methyl carbon-13's while the original Burke-Chan model fails to do so.