Structure, vibrations and relative stability of 1-methylcyclobutene and methylenecyclobutane tautomers using DFT and CCSD methods

Abstract

In this study, geometrical optimizations, infrared spectroscopic analysis and relative stabilities of 1-methylcyclobutene and methylenecyclobutane tautomers were investigated by utilizing high-level ab initio and DFT calculations. The thermodynamic data showed that 1-methylcyclobutene is the more stable isomer with enthalpy [Formula: see text][Formula: see text]kcal/mol and Gibbs energy [Formula: see text][Formula: see text]kcal/mol lower than that for methylenecyclobutane at the M06/aug-cc-PVTZ level of theory. These results are in good agreement with the available experimental data. Additionally, the geometrical parameters and vibrational frequencies agree well with the recorded results in literatures.