An N.M.R. study of ann-butane film on graphite

Abstract

Deuteron magnetic resonance relaxation rates of the n-butane isotopic molecules (CD3)2(CH2)2, (CH3)2(CD2)2, and C4D10 at surface coverage ϑ = 0.8 on the graphitized carbon black Graphon were measured as function of temperature (130 to 290 K) and resonance frequency (13·7 and 52·7 MHz). The motional model which represents the experimental data rather well considers four rotational types of motion proceeding independently of each other: methyl group reorientation, a combined conformational/over-all motion around the central carbon-carbon bond axis, a reorientation about an axis normal to the surface and, finally, an isotropic rotation brought about by surface diffusion. The correlation times of these motions are evaluated. The methyl internal rotor correlation time is in agreement with literature data obtained for solid n-butane.