G. Olah, Arwed Burrichter, G. Rasul
May 1, 1997
Citations
0
Influential Citations
9
Citations
Journal
Journal of the American Chemical Society
Abstract
The protonation of ammonium ions NR4+ (R = H, CH3) to form the corresponding protioammonium dications HNR42+ (R = H, CH3) was investigated by hydrogen/deuterium exchange experiments and by ab initio molecular orbital calculations. Hydrogen/deuterium exchange was observed by 2H NMR spectroscopy at the CH3 groups of tetramethylammonium ion N(CH3)4+ when reacted with excess DF:SbF5 superacid. On the basis of calculational results, the intermediacy of the corresponding C−H-protonated protiotetramethylammonium dication (CH3)3NCH42+ is suggested to account for the observed exchange. Under similar conditions, no exchange was observed in the parent ammonium ion NH4+ in FSO3D:SbF5 superacid, although the NH52+ dication was calculated to be kinetically stable with a considerable barrier to deprotonation. The pentafluoroammonium dication NF52+ was also investigated theoretically, and the results were compared to those of neutral NF5.