Synthesis of 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazol-5(4H)-one and 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazole-5(4H)-thione and solvent effects on their infrared spectra in organic solvents

Yesim S Kara; Mustafa Ünsal; Nalan Tekin; Aslı Eşme

doi:10.1016/j.saa.2020.119424

Synthesis of 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazol-5(4H)-one and 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazole-5(4H)-thione and solvent effects on their infrared spectra in organic solvents

Spectrochim Acta A Mol Biomol Spectrosc. 2021 Apr 15:251:119424. doi: 10.1016/j.saa.2020.119424. Epub 2021 Jan 5.

Authors

Yesim S Kara¹, Mustafa Ünsal², Nalan Tekin², Aslı Eşme³

Affiliations

¹ Kocaeli University, Science and Art Faculty, Department of Chemistry, Umuttepe Campus, 41001 Kocaeli, Turkey. Electronic address: yesimkara@kocaeli.edu.tr.
² Kocaeli University, Science and Art Faculty, Department of Chemistry, Umuttepe Campus, 41001 Kocaeli, Turkey.
³ Kocaeli University, Department of Elementary Science Education, Umuttepe Campus, 41001 Kocaeli, Turkey.

PMID: 33461130
DOI: 10.1016/j.saa.2020.119424

Abstract

In the present study novel 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazol-5(4H)-one (compound (4)) and 4-(4-ethyl-phenyl)-3-(4-methyl-phenyl)-1,2,4-oxadiazole-5(4H)-thione (compound (5)) were synthesized. These oxadiazole ring derivatives were characterized by IR, ¹H NMR, ¹³C NMR and HRMS analyses. The solvent effects on CO, CN and CS stretching vibrational frequencies (ν(CO), ν(CN) and ν(CS)) of synthesized compounds were investigated experimentally using attenuated total reflection (ATR) infrared spectroscopy and compared with the theoretical results assigned using the potential energy distribution (PED) contributions. Furthermore, the ν(CO), ν(CN) and ν(CS) of compound (4) and compound (5) were correlated with empirical solvent parameters such as the solvent acceptor numbers, the Swain equation, the Kirkwood-Bauer-Magat equation, and the linear solvation energy relationships. Apart from the linear effects investigated in similar studies, solvent-induced vibrational shifts were investigated using the quadratic equation. The prediction capabilities of empirical solvent parameters were statistically compared. It was found that the linear solvation energy relationships show better correlation than the other empirical solvent parameters. Additionally, the quadratic equation provided more accurate predictions for the vibrational frequency locations than the Swain and the linear solvation energy relationships equations.

Keywords: Empirical solvent parameters; Infrared spectroscopy; Interaction effects; Oxadiazole ring; Quadratic equation; Solvent effects.