Expanding molecular dynamics simulations to the NMR time scale. I. Studies of conformational interconversions of 1, 1-difluoro-4, 4-dimethylcycloheptane using MM3-MD
✍ Scribed by Fanbing Li; Weili Cui; Norman L. Allinger
- Publisher
- John Wiley and Sons
- Year
- 1994
- Tongue
- English
- Weight
- 809 KB
- Volume
- 15
- Category
- Article
- ISSN
- 0192-8651
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✦ Synopsis
A molecular dynamics (MD) simulation of 35,000 picoseconds (ps) has been carried out to study the conformational interconversions of 1,l-difluoro-4,4dimethylcycloheptane at room temperature using the MM3 force field. The exchange between axial and equatorial fluorine atoms was the only conformational interconversion that occurred, and it took place via the process of pseudorotation. Ring inversions (twist-chair > twist-boat > twistchair) were not observed. The axial-equatorial exchange of the two fluorine atoms took place five times during the MD trajectory of 35,000 ps. The two CH3 groups occupied symmetrical positions (exchangeable by a C2-like rotations, where C2-like means it would be C2 if the fluorines were not present) in the MM3 structures, and during most of the time of the MD trajectory. The methyls occasionally moved off the C2-like axis in the simulated process, mostly because the C2-like axis was momentarily moved so that it did not pass through the ring atom to which the two CH3 groups are