| Abstract
| - Conjugated polyynes are a class of species of diverse and increasing interest. Length-scrambling and substituentscrambling reaction energies were examined using ab initio quantum chemistry calculations to investigateissues concerning the energetic effects of the molecular ends (substituent communication). Computationswere performed for the parent, monohalogenated, and dihalogenated (F, Cl, Br, I) polyynes of up to 60 carbonatoms. A study of resonance effects using natural resonance theory and bond lengths demonstrates lone-pair-donating effects that increase in the series F < Cl < Br < I, but run counter to the halogen inductive effectswhich decrease in this series and dominate energetic effects.
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