Vibrational Spectroscopy Investigation Using Ab Initio and Density Functional Theory Analysis on the Structure of tert-Butyl 3a-Chloroperhydero-2,6a-epoxyoxireno[e]isoindole-5-carboxylate
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The molecular structure, vibrational frequencies, and infrared intensities of the tert-butyl 3a-Chloroperhydero-2,6a-epoxyoxireno[e]isoindole-5-carboxylate were calculated by the HF and DFT (BLYP and B3LYP) methods using 6-31G(d) and 6-31G(d,p) basis sets. The FT infrared spectrum of the solid sample was measured under standard condition. We obtained two stable conformers for the title compound; however Conformer 1 is approximately 0.2kcal/mol more stable than the Conformer 2. The comparison of the theoretical and experimental geometry of title compound shows that the X-ray parameters fairly well reproduce the geometry of Conformer 2. Comparison of the fundamental vibrational frequencies of the title molecule and calculated results by HF and DFT methods indicates the B3LYP is superior for molecular vibrational problems. The harmonic vibrations computed by the B3LYP/6-31G(d,p) methods are in a good agreement with the observed IR spectral data. Theoretical vibrational spectra of the compound were interpreted by means of potential energy distributions (PEDs) using VEDA 4 program.