Non-empirical calculations for minimal energetic reaction pathways of hf molecule addition to acetylene and methylacetylene

Abstract

Potential energy surfaces of gas-phased synchronous addition of HF to acetylene and methylacetylene. A non-empirical Harthree-Fock-Ruthane method (Gaussian-03, G-31++G** basis) with electronic correlation consideration in MP2 approximation (Moeller-Plesseth 2nd grade) was used. Reaction heats and activation energies were calculated. Reaction heat of HF addition to acetylene molecule is -19.5 kcal/mol, activation energy is 52.3 kcal/mol. Reaction heats of HF addition to methylacetylene according to Markovnikov's rule and against it comprise -20.7 and -16.1 kcal/mol; activation energies are 48.0 and 53.5 kcal/mol accordingly. It was established that HF addition to methylacetylene molecule with formation of 2-fluoropropene is more energetically advantageous according to Markovnikov's rule kinetically as well as thermodynamically.

Keywords

• gas-phased reactions
• electrophile
• nucleophile
• acetylene
• methylacetylene
• alkynes
• non-empirical harthree-fock-ruthane method
• gaussian-03
• electronic correlation
• markovnikov's rule
• transition state
• reaction heat
• activation energy