Abstract
This review aims firstly to clarify the meanings of key terms and concepts associated with the idea of the transition state, as developed by theoreticians and applied by experimentalist, and secondly to provide an update to the meaning and significance of the transition state in an era when computational simulation, in which complexity is being increasingly incorporated, is commonly employed as a means by which to bridge the realms of theory and experiment. The relationship between the transition state and the potential-energy surface for an elementary reaction is explored, with discussion of the following terms: saddle point, minimum-energy reaction path, reaction coordinate, activated complex, transition structure, intrinsic reaction coordinate, transition vector, transition-state structure, and transition state. Structural information determined by the application of computational methods to simple systems or inferred from empirical studies is critically discussed in the light of various complications. Consequently, the relationship between the transition state and the free-energy surface for an elementary reaction within a condensed system is explored, with discussion of collective variables, minimum free-energy paths, variational transition-state theory, transmission coefficients, more about reaction coordinates, and equicommittors. It is noted that any visual picture of a transition state is necessarily an average view, and an updated definition of the transition state is proposed.
Original language | English |
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Title of host publication | Advances in Physical Organic Chemistry |
Editors | Ian H. Williams, Nicholas H. Williams |
Publisher | Elsevier Academic Press Inc |
Pages | 29-68 |
Number of pages | 40 |
Volume | 53 |
ISBN (Print) | 9780081029008 |
DOIs | |
Publication status | Published - 2019 |
Publication series
Name | Advances in Physical Organic Chemistry |
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Volume | 53 |
ISSN (Print) | 0065-3160 |
Funding
IHW is grateful to his colleagues on the IUPAC taskforce to update the Glossary of Terms in Physical Organic Chemistry , under the leadership of Professor Charlie Perrin, for stimulating discussions that provided the motivation for writing this chapter. IT acknowledges financial support from Generalitat Valenciana (Project AICO/2018/238) and Ministerio de Educación Ciencia y Universidades of Spain (Project PGC2018-094852-B-C22) and helpful discussions held with Dr. Kirill Zinovjev.
Keywords
- Computational simulation
- Dividing surface
- Equicommittor
- Free-energy surface
- Potential-energy surface
- Reaction coordinate
- Transition state
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry