'Amide resonance' correlates with a breadth of C-N rotation barriers
| Autor: | Carl R. Kemnitz, Mark J. Loewen |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Rotation
Nitrogen Electrons Biochemistry Catalysis chemistry.chemical_compound Colloid and Surface Chemistry Computational chemistry Amide Acetamides Lone pair Basis set Molecular Structure Chemistry Charge (physics) General Chemistry Resonance (chemistry) Amides Carbon Bond length Crystallography Energy Transfer Quantum Theory Thermodynamics Protons Acetamide |
| Zdroj: | Journal of the American Chemical Society. 129(9) |
| ISSN: | 0002-7863 |
| Popis: | Complete basis set calculations (CBS-QB3) were used to compute the CN rotation barriers for acetamide and eight related compounds, including acetamide enolate and O-protonated acetamide. Natural resonance theory analysis was employed to quantify the "amide resonance" contribution to ground-state electronic structures. A range of rotation barriers, spanning nearly 50 kcal/mol, correlates well to the ground-state resonance weights without the need to account for transition-state effects. Use of appropriate model compounds is crucial to gain an understanding of the structural and electronic changes taking place during rotation of the CN bond in acetamide. The disparate changes in bond length (DeltarCODeltarCN) are found to be consonant with the resonance model. Similarly, charge differences are consistent with donation from the nitrogen lone pair electrons into the carbonyl pi* orbital. Despite recent attacks on the resonance model, these findings demonstrate it to be a sophisticated and highly predictive tool in the chemist's arsenal. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|