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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 16, Number 3
JKCSEZ 16(3)
June 20, 1972 

 
Title
Electronic Structure of Flavins. Inclusion of Methyl Groups in Molecular Orbital Treatments of Flavins
Author
Pill-Soon Song
Keywords
Abstract
Various MO methods with differing degrees of sophistication are shown to yield qualitatively consistent results for methyl isoalloxazines. However, with crude methods such as the HMO and ω-technique, the choice of Coulomb and resonance integralsis critical, in contrast with simpler molecular systems. The empirical value of ω = 0.5 appears to be more reasonable than 1.4. Methyl groups in these flavins are best treated by the group orbital approximation. The pseudo-hetero atom approximation overestimates methyl hyperconfiguration with the Pariser-Parr-Pople SCF MO method. Singlet π → π*transition energies are calculated by the P-P-P method and agree reasonably with the experimental values. 2-and 4-Thioisoalloxazine analogs are also treated. Reactivity indices of the flavin molecule are presented, including superdelocalizability, frontier orbital and radical densities. Various aspects of the applications of these indices to some chemical and biological reactivities of flavins are briefly discussed. The effects of the methyl groups on dipolemoments, ionization potentials, electron affinities, and spectra are described in detail.
Page
119 - 134
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