The rotatinghyphen;frame nuclear magnetic relaxation timeT1rgr;has been measured for 10 normal alkanes ranging from C4H10to C94H190. Data were obtained within the range minus;200deg; to +70deg;C for C94H190, C40H82, and C6H14. The highhyphen;temperature region is characterized by a process of high activation energy ascribed to chain rotation while the lowhyphen;temperature region exhibits aT1rgr;minimum arising from coupling of the entire spin system to the methylhyphen;group rotation via spin diffusion. This information and the analogousT1data yield an activation energy of 2.6 kcal/mole for the methylhyphen;group rotation. The remaining compounds were examined in the vicinity of theT1rgr;minimum at minus;190deg;C and relaxation times characterizing the intrinsic methyl relaxation and spinhyphen;diffusion process have been extracted from the data for three rf field strengths. Theoretical estimates of the spinhyphen;diffusion coefficients at low fields and methylhyphen;proton relaxation times are in satisfactory agreement with the observed quantities.
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