摘要：

The absorption and circular dichroism (CD) data for a series of alkyl aryl sulfoxides 1–16 of known S configuration have been analyzed. The strong bathochromic effect exerted by the nitro group in the para position of the phenyl sulfoxides indicates that the sulfur atom acts as an electron donor moiety towards the phenyl ring. Such behavior requires a significant 2p(C)–3sp³(S) overlap, and therefore the phenyl (and p-substituted phenyl) sulfoxides 1—-12, as well as the 2-naphthyl sulfoxides 15 and 16, must assume a conformation which permits such orbital overlap. The steric effect of the peri hydrogen in 1-naphthyl-substituted compounds 13 and 14 does not allow a conformation of this type, and in these compounds the above-mentioned 2p(C) and 3sp³(S) orbitals are positioned in almost orthogonal planes. This conformational difference is clearly shown by the absorption spectra: compounds 1–12, 15, and 16 show the lowest energy σσ* di più bassa energia del cromoforo solfossidico a circa 250 nm, suggerendo la presenza di un cromoforo S=O coniugato. Al contrario, in 13 e 14 lo stesso assorbimento si trova a circa 200 nm, indicando la presenza di un cromoforo S=O isolato. Gli spettri di DC di 13 e 14 presentano una specie di couplet eccitonico negativo tra 250 e 200 nm. Tale andamento spettrale può essere attribuito all'accoppiamento eccitonico tra la trans

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