High resolution 2H NMR spectroscopy at the natural abundance level of deuterium

Abstract

The relaxation time, T1, of deuterium nuclei in a few deuterated compounds, such as methanol-d4, benzene-d6, and dimethylsulfoxide-d6, is measured at higher temperatures in the range from 300 to 375 K. An almost linear increase in time, T1, over an increase in temperature is observed in all these cases, which confirms an increase in the mobility of molecules and a decrease in the correlation time. A T1 value in the range from 2 to 3 s can be expected for deutrons in small organic molecules at temperatures above 350 K. Thus, a linewidth of about 0.1 Hz in 2H NMR spectra can be obtained for a magnetic field inhomogeneity of about 0.5 Hz in 1H NMR spectra. Such high resolution 2H NMR spectra provide information about chemical shifts and J(H-D) spin-spin coupling constants (or J(H-H) = (γH/γD)J(H-D) when the isotope effects on the spin-spin coupling constants are neglected), including information about coupling constants between magnetically equivalent protons that can not be observed in 1H NMR spectra. New or refined data on the coupling constants are obtained from the studied 2H NMR spectra for ethanol, propanol, 1,2-dichloroethane, and 1,4-dioxane.