Title:Correlations between Quantum Calculations and the Contribution of Factors
Affecting the Structural Stability and Electronic Properties of Vinyl
Azide and Vinyl Isocyanate
Volume: 20
Issue: 10
Author(s): Hengameh Fallah, Hooshang Atabaki*, Leila Moharrery, Neda Hasanzadeh*Hooriye Yahyaei
Affiliation:
- Department of Chemistry, Islamic Azad University, Arak Branch, Arak, Iran
- Department of Chemistry, Islamic Azad University, Ahvaz
Branch, Ahvaz, Iran
Keywords:
Vinyl azide, vinyl isocyanate, Natural Bond Orbital (NBO), pauli exchange type repulsion, PETR, dipole moments.
Abstract: The conformational features of vinyl isocyanate (1) and vinyl azide (2) have been analyzed
using G4MP2, CCSD(T)/6-311+G**, B3LYP/6-311+G** and LC-ωPBE/6-311+G** theory levels.
Published experimental data indicate that the stability of the cis-isomer of vinyl azide (2) is more than
the trans-isomer. This is consistent with the findings attained using G4MP2 and LC-ωPBE/6-
311+G** levels, whereas B3LYP/6-311+G** and CCSD (T)/6-311+G** levels provide false energetic
outcomes. Natural Bond Orbital (NBO) interpretation is used to interpret the reason for the stability
of the cis stereoisomer of compound 2 and the structural features of compound 1. Dipole-dipole interactions,
steric effects, and resonance energies on the structural behaviors of compounds 1 and 2 are
also investigated using NBO analysis. The results showed that the stability of the cis conformer of
compound 2 compared to its trans conformer could be explained using the steric effect (Pauli Exchange
Type Repulsion or PETR). Dipole moments of the cis conformer of compound 2 are evaluated
experimentally (from Rotational Spectroscopy) and theoretically. The experimental (from Rotational
Spectroscopy) and theoretically evaluated dipole moments of trans-conformation of compound 2 are
slightly greater than that in cis-conformation, which is in favor of the cis-conformation, while dipoledipole
interactions are in favor of the cis-conformation of compound 1. Accordingly, the electrostatic
interactions associated with dipole-dipole interactions do not explain the conformational behaviors of
compound 1. The stabilization energies related to the delocalization of electrons are in favor of the
cis-conformation of compound 1, whereas it has no considerable effect on compound 2’s conformational
behavior.