responsible for the slow rates. In addition, the N+ methyls of 4a and 4b, which are magnetically nonequivalent by 13C NMR at low temperatures, undergo signal averaging with increasing temperature, the result of rotation dynamics around the ring−N+ bonds giving for 4b in acetone-d6 ΔH⧧ and ΔS⧧, respectively, of 7.2 kcal/mol and −9 eu. Similar values are found for tert-butyl rotation in 3 in Et2O-d10. Around