FT-IR, FT-Raman spectra, density functional computations of the vibrational spectra and molecular conformational analysis of 2,5-di-tert-butyl-hydroquinone

The purpose of finding conformer among six different possible conformers of 2,5-di-tert-butyl-hydroquinone (DTBHQ), its equilibrium geometry and harmonic wavenumbers were calculated by the B3LYP/6-31G(d,p) method. The infrared and Raman spectra of DTBHQ were recorded in the region 400–4000 cm−1 and 50–3500 cm−1, respectively. In addition, the IR spectra in CCl4 at various concentrations of DTBHQ are also recorded. The computed vibrational wavenumbers were compared with the IR and Raman experimental data. Computational calculations at B3LYP level with two different basis sets 6-31G(d,p) and 6-311++G(d,p) are also employed in the study of the possible conformer of DTBHQ. The complete assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated using VEDA 4 program. The general agreement between the observed and calculated frequencies was established.

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► Molecular geometry and vibrational assignments were carried out for DTBHQ.
► Conformational analysis was performed with the help of Spartan 08 program.
► PED calculations were also made using VEDA 4 program.
► All the calculations were performed by B3LYP/6-31G(d,p) method.
► DTBHQ is mainly used as an inhibitor, antioxidant and stabilizer.