
%0 Journal Article
%A Baldwin, WG 
%A Stranks, DR 
%T Rates of substitution of the hydrated beryllium cation by hydrogen fluoride and fluoride ion
%J Australian Journal of Chemistry
%D 1968/09/01
%V 21
%N 9
%P 2161-2173
%K 
%R https://doi.org/10.1071/CH9682161
%U https://www.publish.csiro.au/paper/CH9682161 
%X The rate of formation of the monofluoroberyllium species Be(OH2)3F+ was measured by a conductimetric stopped-flow technique. At acid concentrations exceeding 0.01M two parallel reaction paths were identified:     Be(OH2)42+ +F- &#8596; Be(OH2)3F+     (k1,k-1)    Be(OH2)42+ +HF- &#8596; Be(OH2)3F+H+(k2,k-2)    At 25º and an ionic strength of O.2M, k1 = 724 ± 95 l. mole-l sec-1 and k2 = 73 ± 3 l. mole-1 sec-1. Both substitution paths exhibit activation energies of 8.9 ± 0.8 kcal/mole. The data are interpreted in terms of an SN11P mechanism which is also proposed for the analogous Be2+ + SO42- reaction. Outer-sphere ion pairs of Be(OH2)42+ with respectively F-, HF, and SO42- undergo substitution with the same activation energy. A linear free energy relation exists between the rate of formation of the inner-sphere complexes from the outer-sphere ion pairs and the accompanying free energy changes. 
