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Geometry, force field, and fundamental frequencies of 4a,4b-dihydrophenanthrene, a scaled quantum-mechanical force field study

✍ Scribed by Xuefeng Zhou; Ruifeng Liu

Publisher: Elsevier Science
Year: 1992
Tongue: English
Weight: 401 KB
Volume: 191
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(92)85412-4

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✦ Synopsis

Geometries of both cis-and trans-4a,4b-dihydrophenanthrene are optimized by restricted Hartree-Fock method with 4-21G basis. At this level of theory, the trans-conformer is predicted 8.0 kcal/mol lower in energy than the cis one. The quadratic force field of the trans-conformer obtained from empirical scaling of the ab initio force constants reproduced the observed frequencies with mean deviation of about 10 cm-~. Based on the calculation an earlier assignment of two observed frequencies is confirmed and assignment of the rest of the observed frequencies is given. The observed frequencies at 1555 and 1534 cm-~ are concluded not to be fundamental frequencies of the subject molecule. This study shows again the practical value of the scaled quantummechanical force field method in the assignment of fundamental frequencies and identification of reaction products.

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