Spatial and electronic structure of vinyl and allenyl chalcogenides

Alkyl vinyl chalcogenides show a complex picture of rotational isomerism and are characterised by the presence of several qualitatively different types of stable conformers. The features of conformational structure of these compounds can be understood only by considering the stationary states altogether. Conformational analysis of divinyl chalcogenides indicates that the potential energy surface of internal rotation should be considered not as just a source of information on rotational isomerism; rather, it is a tool in a search for stationary states corresponding to definite intervals of variation of internal molecular coordinates. The principal details of the orbital structure of allenyl ethers and vinyl chalcogenides including a weak dependence of the structure and relative location of higher occupied π-MOs of alkyl vinyl chalcogenides on the nature of the heteroatom and the structure of the alkyl substituent are discussed. The common feature of chalcogenides is the presence of a low energy excited state of σ-symmetry. The excited states of π-symmetry are always located higher on the energy scale than the states of σ-symmetry. The bibliography includes 198 references.