Nonempirical calculations of the potential-energy fields of the nucleophilic addition of H⁻ and F⁻ to acetylene and methylacetylene molecules

Abstract

By using the basis 3–21 + G, the minimum-energy routes for the nucleophilic addition to the F⁻ ion to methylacetylene have been calculated within the framework of the Hartree-Fock-Roothaan method according to and against the Markovnikov rule with the formation of the 1-fluoropropenyl and 2-fluoropropenyl anions. The results have been compared with data from previous calculations of the nucleophilic addition of H⁻ and F⁻ to acetylene with the formation of vinyl and fluorovinyl anions, as well as of the nucleophilic addition of H⁻ to methylacetylene according to and against the Markovnikov rule with the formation of the 1-propenyl and 2-propenyl anions. It has been established that the reaction with H⁻ is exothermic, while the reaction with F⁻ is endothermic. The activation energies of the reactions with F⁻ are lower than the activation energies of the corresponding reactions with H⁻. It is shown that the reactions with H⁻ have a relatively “early” transition state, while the reactions with F⁻ are characterized by a “later” transition state.