Lattice energies and thermochemical radii of the anions OR- (R=2-Me; 2,6-Me-2; 2,4,6-Me-3; 2,6-t-Bu-2) in alkali metal phenoxides, MOR (M=Li, Na, K, Rb and Cs) were investigated based on the corresponding standard molar enthalpies of formation determined by reaction-solution calorimetry. The results obtained at 298.15K were as follows: Delta(f)H degrees(m) (MOR, cr)/kJmol(-1)=-398.4 +/- 1.1 (LiO-2-MePh), -423.4 +/-1.6 (LiO-2,6-Me2Ph), -457.3 +/- 7.1 (LiO-2,4,6-Me3Ph), -346.6 +/- 1.4 (NaO-2-MePh), -399.1 +/- 1.5 (NaO-2,6MeYh), -422.4 +/- 7.1 (NaO-2,4,6-Me3Ph), -496.6 +/- 7. 1 (NaO-2,6-t-Bu2Ph), -367.8 +/- 1.2 (KO-2-MePh), -399.1 +/- 1.4 (KO-2,6-Me(2P)h), -368.8 +/- 1.2 (RbO-2-MePh), -403.6 +/- 1.3 (RbO-2,6-MeYh), -387.0 +/- 1.6 (CsO-2-MePh) and -413.6 +/- 1.3 (CsO-2,6-MeYh). Estimates of thermochemical raddi, lattice energies and standard enthalpies of formation of not experimentally measured alkali metal phenoxides was successfully done with a model based on the Kapustinskii equation and the set of values experimentally determined. (c) 2005 Elsevier B.V. All rights reserved.