Quantitative 2 H NMR spectroscopy. 1. Thermodynamic H/D isotope effects in N , N -dimethylformamide and cyclopentadiene molecules

Abstract

A new method for quantification of the relative distribution of deuterium in molecules is proposed. The technique is based on the lineshape analysis in the 2H NMR spectra obtained at the natural abundance level of deuterium with allowance for inhomogeneity of the magnetic field. The equilibrium thermodynamic H/D isotope effects for hindered rotation about the C—N bond in the N,N-dimethylformamide molecule and for prototropic exchange in the cyclopentadiene molecule were determined. The results obtained agree with those of DFT calculations of the vibrational energies.