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KMID : 1059519850290020098
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Journal of the Korean Chemical Society
1985 Volume.29 No. 2 p.98 ~ p.103
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PMO Theory of Orbital Interaction (Part 6). Sigma-Aromatic Orbital Interactions in Heteroatom Analogues of Trimethylene Diradical
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Lee Ik-Choon
Kim Ho-Soon
Choi Jae-Ho
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Abstract
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Orbital interactions between two nonbonding orbitals have been investigated for heteroatom analogues of trimethylene diradical using MINDO/3 and STO-3G methods. The results showed that the conformers in which significant σ-aromatic stabilization is involved exhibited level order reversal to n- below n+ as it was found for trimethylene diradical. Lone pair orbitals (LPO) were found to be stabilized by charge dispersion accompanying vicinal trans n-σ* interaction and hydrogen bonding. In systems with different heteroatoms, N and O, the contribution of the LPO of oxygen, nO was always greater in the lower level whereas that of nitrogen, nN, was greater in the higher level as can be expressed as : n±(lower) = nO ± λNnN. n±(higher) = nN ± λOnO. where λi〈 1.0.
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KEYWORD
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