Hydrogen bonding. Part 86: DFT molecular orbital study of the first hydration shell of N,N,N-trimethyl-1-adamantylammonium ion

Hydrogen bonding. Part 87: DFT MO study of hydration of tetramethyl- and tetraethylammonium ions – Correlation of hydrate symmetry with 14N to CH NMR coupling

“…It is not symmetrically placed, but occupies a position slightly off center from the C 3 axis of the cation, where it accepts two aACH 3 hydrogen bonds from two separate CH 3 groups. This type of bonding (Type A) is identical to that shown by the first H 2 O to attach to 3MAA + [3]. Three subsequent H 2 O add to 4MA + and occupy similar Type A positions over the remaining three triangular faces of the cation to yield 4MA4W.…”

“…Although HF/3-21G * gives inflated attraction energies as a result of basis set superposition error [8][9][10], we have observed on many occasions (for example see ref. [3]) that it gives the same hydrate structures as higher level calculations. These preliminary studies demonstrated that two different 4EA6W structures could evolve, and this was confirmed by calculations at the B3LYP/6-31G ** level.…”

“…We recently [3] used B3LYP/6-31G ** calculations to examine the hydration of the N,N,N-trimethyl-1-adamantylammonium ion (3MAA + ) which was shown to form a tightly bound primary hydration structure with 10H 2 O molecules, in accord with solubility and NMR observations. The present work is undertaken to apply the same techniques to the hydration of 4MA + and 4EA + .…”