The reactive intermediate in acetylene polymerization: Results of quantum chemical calculations on charge delocalization and its consequences

The charge delocalization in the conjugated vinyl intermediates, which are assumed to be the reactive intermediates in acetylene polymerization, is calculated, taking into account σ as well as π electrons. Delocalization is shown to exist, but it is of a different kind for cations and anions. In the anion, the σ charge is localized at the reactive center and the π change is displaced into the system. In the cations, the σ charge flows towards the reactive center and the π charge is more or less unaffected. π‐overlap charges between the carbon atoms are much less affected than in the case of the corresponding allyl type anion and cation. The calculated charge delocalizations are compared with the little experimental evidence there is, and possible implications of σ and π delocalizations on reactivity and specificity of reaction are discussed.