Solvent effects on the thermochemistry of free-radical reactions

Autor:	D. Griller, J. M. Kanabus-Kaminska, B. C. Gilbert
Rok vydání:	1989
Předmět:	Standard enthalpy of reaction Chemistry Radical Solvation Free-radical reaction General Chemistry Biochemistry Bond-dissociation energy Chemical reaction Catalysis Colloid and Surface Chemistry Thermochemistry Physical chemistry Solvent effects
Zdroj:	Journal of the American Chemical Society. 111:3311-3314
ISSN:	1520-5126 0002-7863
DOI:	10.1021/ja00191a030
Popis:	Heats of the reaction H{sub 2}O + 2RH {yields} 2H{sub 2}O + 2R{sup {sm bullet} were measured in water for a variety of organic substrates by using photoacoustic calorimetry. The values obtained were substantially lower than those calculated from gas-phase data and the difference was due entirely to the change in solvation energy associated with the conversion of 1 equiv of hydrogen peroxide to 2 of water. The solvation energies of R{sm bullet}} and RH were the same and their contributions to the measured heats of reaction therefore canceled. The results suggest that solution data, measured in extremely polar solvents, can be converted to their gas-phase equivalents (and vice versa) by considering only the heats of solvation of very small, polar molecules that participate in a given reaction. Moderately large organic molecules and their corresponding radicals are solvated to the same extent - even in water.
Databáze:	OpenAIRE
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