Quadrupolar relaxation effects in methyl-substituted ammonium ions as determined by 1H nuclear magnetic resonance

Abstract

Nitrogen-14 quadrupole interactions broaden the 1H nuclear magnetic resonances of the ammonium protons spin-coupled to 14N in the methyl-substituted ammonium chlorides (methylammonium, dimethylammonium, and trimethylammonium). These proton lineshapes have been determined over the temperature range −8.3 to +93.6 °C in 6 mol L−1 aqueous HCl solution. The 14N spin-lifetimes, τ, have been calculated from the Arrhenius form equation In τ vs. 1/T (K), and yield activation energies of 10.63 ± 0.92, 10.60 ± 0.52, and 11.12 ± 0.39 kJ mol−1 for the mono-, di-, and tri-methyl species, respectively. The 14N nmr linewidths have been extracted from these data and a comparison is made with 14N nmr spectra obtained by Ogg and Ray.