New insights into the conformal stability, influence of hydrogen bonding and vibrational analysis of 2,6- and 3,5-Dihydroxyacetophenone – A comparative study

• Structural conformers were identified with the help of PES scan analysis and B3LYP/6-31G** DFT calculations.
• Influence of intramolecular hydrogen bonding and intra-molecular charge transfer has been thoroughly investigated.
• Selective scaling was carried out on calculated wavenumbers.
• A complete assignment of observed fundamentals has been done based on PED.
• Electronic excitation was studied using HOMO-LUMO and UV–Vis studies.

The conformal stability of 2,6-Dihydroxyacetophenone (DHAP I) and 3,5-Dihydroxyacetophenone (DHAP II) were investigated using Potential Energy Surface scan studies and B3LYP/6-31G** level Density Functional Theory(DFT) calculations. The experimental (FT-IR and FT-Raman) spectra were recorded in the condensed phase in order to perform detailed vibrational analysis. The optimized geometry and vibrational wavenumbers were determined by using B3LYP/6-31G** level Density Functional Theory calculations. The effect of scaling on the calculated wavenumbers was analyzed by employing unscaled, uniform scaling and selective scaling procedures. A detailed comparative analysis on the effect of hydrogen bonding on the geometry, structural parameters and vibrational wavenumbers has been carried out using the results obtained from PES scan and DFT level calculations. The results from the above studies reveals that, the presence of strong intramolecular hydrogen bond in DHAP I has significantly altered the geometrical parameters and hence the vibrational wavenumbers. The hydrogen bonding in DHAP I is strong enough to make it more stable compared to that of DHAP II.

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