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Substituent effects on O-H bond dissociation enthalpies: a computational study
Kenneth B Wiberg1, G Barney Ellison, J Michael McBride
1Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, USA. kenneth.wiberg@yale.edu
The Journal of Physical Chemistry. A
|December 5, 2012
Summary
This study accurately calculated hydroxyl radical bond dissociation enthalpies (BDEs) using CBS-APNO methods. Lone pair conjugation in adjacent atoms significantly influences BDEs, explaining their wide experimental range.
Area of Science:
- Physical Chemistry
- Computational Chemistry
- Quantum Chemistry
Background:
- Bond dissociation enthalpies (BDEs) are crucial for understanding chemical reactions.
- Substituent effects can cause significant variations in BDEs, particularly for hydroxyl (OH) bonds.
Purpose of the Study:
- To accurately reproduce and extend experimental OH bond dissociation enthalpy data.
- To investigate the influence of substituent effects, specifically lone pairs adjacent to oxygen, on OH BDEs.
Main Methods:
- Utilized the CBS-APNO computational method to calculate BDEs.
- Compared computational results with experimental OH BDE data.
- Analyzed the relationship between BDEs and electronic properties like spin density and bond order.
Main Results:
- CBS-APNO calculations accurately reproduced the experimental range of OH BDEs.
- Identified lone pair conjugation on atoms adjacent to oxygen as the primary factor for wide BDE variations.
- Established linear relationships between BDEs and spin density at the radical center.
- Observed linear correlations between BDEs and the change in X-O bond order from X-O-H to X-O·.
Conclusions:
- Computational methods like CBS-APNO are reliable for predicting BDEs.
- Conjugation effects involving lone pairs are key determinants of OH BDE variability.
- Spin density and X-O bond order changes serve as useful indicators for BDE trends.
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