A correlation of the energy barrier opposing cation reorientation in ammonium compounds with thermochemical data
Abstract
There is a good linear correlation between the energy barrier opposing cation reorientation in a compound (NH4)nX, and the quantity Δ(Xn–)={ΔHf⊖[(NH4)nX,s]–ΔHf⊖(RbnX,s)}/n, and at zero barrier height, Δ(Xn–) is about 143 kJ mol–1; depressions below this threshold provide some measure of cation–anion hydrogen bonding in (NH4)nX, and the estimated value of ΔHf⊖(NH4+,g), derived from the threshold, is 638 kJ mol–1.