Abstract

Pinak Dutta¹* and Mita Dutta²

Hemiacetals being unstable compounds are difficult to isolate and it is difficult to establish their structure and spectroscopic properties by experiment. IR and NMR experimental data are available in the literature only for the hemiacetal 1-methoxy ethanol in a reaction mixture. The objective of the present work is to investigate how the methods based on density functional theory (DFT) and its time dependant version (TDDFT) can predict structural and spectroscopic properties of this unstable compound. Geometry optimization and frequency calculations have been carried out by DFT method at 6-31+G(d) and 6-31++G(d,p) levels. The UV-Vis spectra in a number of solvents have been calculated by the TDDFT method under the polarizable continuum model and the variation of the calculated UVvis absorption peak with two solvent polarity indices (namely, ET(30) and Z-values) has been studied in these solvents; electronic transition energies at the λmax values in the theoretically calculated spectra increase with solvent polarity. The calculated infrared absorption bands and NMR chemical shifts (1H and 13C) are in good agreement with reported experimental data. In case of IR, consideration of anharmonicity effect yields better agreement with experiment.

Hemiacetal; 1-Methoxy ethanol; Solvent polarity indices; TDDFT; Anharmonicity

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