National Research Council of Canada. Security and Disruptive Technologies
The ²H nmr lineshapes of a number of tetramethylammonium salts have been studied as a function of temperature. It is shown from this and previous evidence that in certain cases the lowest temperature motions should be assigned to whole ion C'₃ or pseudo-isotropic motion, rather than to methyl group motions as has been assumed in previous ¹H nmr studies. Steric potential calculations have been used to investigate a previously suggested model of concerted partial reorientations of methyl groups.
Canadian Science Publishing
Canadian Journal of Chemistry64, no. 7: 1298–1304.