A b i n i t i o studies of polyenes. I. 1,3-butadiene

Publisher Website
Google Scholar
Abstract
The potential energy function about the C–C single bond for the ground state 1,3‐butadiene has been derived from ab initio calculations at both the Hartree–Fock (HF) level with 6‐31G, 6‐31G*, and 6‐311G** basis sets and the second‐order Mo/ller–Plesset perturbation (MP2) level with 6‐31G* basis set with the complete geometry optimizations at each of 15 fixed CCCC dihedral angles; the total energies and optimized geometries for the s‐trans, gauche, and s‐cis conformers were also determined at MP2 level with 6‐311G* basis set and the third‐order Mo/ller–Plesset perturbation (MP3) level with 6‐31G* basis set. The second stable conformer of the butadiene is predicted to be a gauche structure from all the calculations with a CCCC dihedral angle between 35° and 40° and a barrier of 0.5–1.0 kcal/mol to the s‐cis transition state, and the theoretical torsional potentials are in good agreement with the experimental potential function of trans–gauche–gauche case derived by Durig et al.; by contrast, the theoretical torsional components differ significantly from the experimental results obtained from a trans–cis model. Vibrational frequencies and force field for s‐trans and gauche conformers of 1,3‐butadiene are determined at the Hartree–Fock and MP2 levels with 6‐31G, 6‐31G*, 6‐311G, and 6‐311G* basis sets. The mean absolute percentage deviations of the calculated frequencies from the experimental values (not corrected for anharmonicity) are ∼10%–13% and 3%–6% for the Hartree–Fock and MP2 methods, respectively. The effects of polarization functions and electron correlation on the force fields are studied, and the additivity of correlation and d function effects are discussed. Comparisons are made with other force fields, including experimental and previous ab initio results.

This publication has 82 references indexed in Scilit: