NMR relaxation studies on testosterone in solution. Computer-assisted analysis of 13C T1 data measured at different temperatures

Abstract

NMR ¹³C relaxation times have been measured for testosterone in [²H₆]DMSO at various temperatures. The data were processed by a computer-assisted method of analysis based on several molecular reorientational motion models. As a result of this study, activation energies have been determined for the molecular motion. From an analysis of the temperature-dependent ¹³C T₁ of quaternary carbon atoms, it is seen that the spin-rotation and chemical-shift-anisotropy mechanisms contribute significantly to the quaternary sp² carbons whereas only the spin-rotation mechanism contributes to the quaternary sp³ carbons. The experimental relaxation times differ appreciably for the two methyl groups, indicating a difference in the barriers to internal rotation.