Related Experiment Videos
Conformational Study of Oxacyclooctan-2-one by Dynamic NMR Spectroscopy and Computational Methods
Diwakar M. Pawar1, Erica M. Moody, Eric A. Noe
1Department of Chemistry, Jackson State University, Jackson, Mississippi 39217-0510.
The Journal of Organic Chemistry
|October 25, 2001
Summary
This study reveals oxacyclooctan-2-one exists in two conformations at low temperatures, with distinct energy barriers for molecular rotation. Computational methods confirm these findings, elucidating the molecule's conformational dynamics.
Area of Science:
- Organic Chemistry
- Physical Chemistry
- Computational Chemistry
Background:
- Conformational analysis of medium-sized rings is complex.
- Understanding molecular dynamics is crucial for predicting chemical behavior.
Purpose of the Study:
- To investigate the conformational landscape of oxacyclooctan-2-one.
- To determine the energy barriers associated with conformational changes.
Main Methods:
- Variable-temperature carbon-13 and proton nuclear magnetic resonance (NMR) spectroscopy.
- Molecular mechanics (MM3) and ab initio (HF/6-311G, MP2/6-311G) calculations.
Main Results:
- Two distinct conformations of oxacyclooctan-2-one were identified at -154.2°C with populations of 25.6% and 74.4%.
- Free-energy barriers for carbonyl carbon peak coalescence were 6.98 and 7.23 kcal/mol.
- A free-energy barrier of 9.16 kcal/mol was associated with geminal proton exchange.
Conclusions:
- The observed conformations possess the E configuration of the lactone group.
- The conformational behavior resembles the boat-chair conformation of cyclooctane.