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Molecular structure and electronic spectrum of taspine: Semiempirical calculations
Author(s) -
Sato Tsuguo,
Kataoka Masahiro
Publication year - 1999
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570360443
Subject(s) - cndo/2 , chemistry , enantiomer , intramolecular force , electronic structure , spectral line , computational chemistry , optical rotation , molecular physics , crystallography , stereochemistry , molecule , organic chemistry , physics , astronomy
AM1 calculations show that taspine has the three energy‐minima along the rotation‐like nuclear displacement of the dimethylaminoethyl group. They correspond to two enantiomeric structures and a Cs structure, which have nearly equal energies. The energy barrier between the enantiomeric structures and the Cs structure is calculated to be about 1 kcal/mol. The small barrier readily causes an intramolecular interconversion of the two enantiomers through the Cs structure and thus results in the optical inactivity of taspine. CNDO/S calculations show that the electronic spectra of the enantiomer and the Cs structure are quite similar. These calculated spectra are in good agreement with the observed electronic spectra.