A 2H NMR study of the solid-phase behavior of nonadecane

Abstract

The ²H NMR spectra of perdeuterononadecane and several specifically deuterated nonadecanes, in solid phases I (orthorhombic) and II (rotator), are reported. In phase I, the central portion of the chain is static on the time scale of 10⁻⁵ s; however, the chain ends are subject to torsional motions. In phase II, the chains undergo hindered rotation. The phase II spectra of the methylene groups located in the center of the chain can be simulated with a model in which the rigid chain undergoes 82° jumps between equivalent sites. However, this model is inadequate for the methyl and methylene groups near the chain ends. The data suggest higher amplitudes of torsional motion in these positions.