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Physical Chemistry Division (I)


Number: 120/15/95

Title: Thermochemistry of chemical reactions: nomenclature, symbols and experimental methods for bond energies

Coordinator(s): M. Ribeiro da Silva

Nomenclature and symbolism for bond energies are, at the moment, somewhat confusing although these quantities are widely used to estimate the thermochemistry of species for which the enthalpies of formation are unknown. The proliferation of designations and symbols for quantities variously known as bond strengths, bond enthalpies, bond energies, bond dissociation enthalpies, bond enthalpy terms, stepwise bond dissociation energies, intrinsic bond energies, BDE,D etc clearly requires some standardisation. Several experimental techniques are available to determine the parameters named above but can only be used to study the thermochemistry of long-lived molecules. However, modern techniques have made possible the study of these species. The correct relationship between the quantities measured with some of these new techniques and thermodynamic functions are often not straightforward and deserve a careful analysis. It is therefore proposed that this project considers in the first stage a comprehensive list of methods that have been used to derive energetic data. A second stage will involve a description of each method with an analysis of its basic assumptions and how thermodynamic data can be derived. In addition recommendations of standard nomenclature and symbols for bond energetics would be prepared.

Progress in the first two years has been very good. A draft of the basic information to be included in the report has already been circulated for approval. In the next period comments will be incorporated and the descriptive material added.

A draft of the paper has been now prepared and is awaiting final comments before being submitted for publication.

A manuscript is being prepared for publication in Pure Appl. Chem. A final document is submitted to public review comments until 30 September 2002. > see provisional recommendations

Dec 2007 - a revised draft is being finalized and shall be available mid 2008.

July 2008 - A draft titled 'Thermochemistry of Chemical Reactions: Terminology and Symbols' is submitted to public review comments until 30 December 2008 > see provisional recommendations

Last Update: 30 July 2008


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