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Pure Appl. Chem., 2007, Vol. 79, No. 8, pp. 1369-1382

Bond-dissociation enthalpies in the gas phase and in organic solvents: Making ends meet

Rui M. Borges dos Santos1, Benedito J. Costa Cabral2,3 and José A. Martinho Simões3

1 Institute for Biotechnology and Bioengineering, Centre for Molecular and Structural Biomedicine, University of Algarve, Gambelas Campus, 8005-139 Faro, Portugal
2 Group of Mathematical Physics of the University of Lisbon, Av. Professor Gama Pinto 2, 1649-003 Lisbon, Portugal
3 Department of Chemistry and Biochemistry, Faculty of Science, University of Lisbon, 1749-016 Lisbon, Portugal

Abstract: Solvent effects are responsible for the difference between gas- and solution-phase bond-dissociation enthalpies (BDEs), and are thus crucial for understanding reactivity in solution. While solvation effects can be negligible (e.g., in reactions involving carbon-centered radicals), they may be rather significant (e.g., when oxygen-centered radicals are formed). This paper reviews a number of models which have been proposed to deal with the difference between the solvation energetics of a radical and its parent molecule. It is concluded that the radical-solvent interaction may be larger than previously anticipated.