Analysis of tautomeric equilibrium in (E)-4,6-dibromo-2-[(4-fluorophenylimino)methyl]-3-methoxyphenol compound

Çiğdem Albayrak Kaştaş; Gökhan Kaştaş; Mahmut Gür; Halit Muğlu; Orhan Büyükgüngör

doi:10.1016/j.saa.2015.07.030

Analysis of tautomeric equilibrium in (E)-4,6-dibromo-2-[(4-fluorophenylimino)methyl]-3-methoxyphenol compound

Spectrochim Acta A Mol Biomol Spectrosc. 2015 Dec 5:151:731-8. doi: 10.1016/j.saa.2015.07.030. Epub 2015 Jul 7.

Authors

Çiğdem Albayrak Kaştaş¹, Gökhan Kaştaş², Mahmut Gür³, Halit Muğlu⁴, Orhan Büyükgüngör⁵

Affiliations

¹ Sinop University, Faculty of Arts and Sciences, Department of Chemistry, 57000 Sinop, Turkey. Electronic address: calbayrak@sinop.edu.tr.
² Ondokuz Mayıs University, Civil Aviation College, Samsun, Turkey.
³ Kastamonu University, Faculty of Forest, Forest Industry Engineering, Kastamonu, Turkey.
⁴ Kastamonu University, Faculty of Arts and Sciences, Department of Chemistry, Kastamonu, Turkey.
⁵ Ondokuz Mayıs University, Faculty of Arts and Sciences, Department of Physics, 55139 Kurupelit-Samsun, Turkey.

PMID: 26172460
DOI: 10.1016/j.saa.2015.07.030

Abstract

In this study, the tautomeric equilibrium between the phenol-imine and keto-amine structural forms of (E)-4,6-dibromo-2-[(4-fluorophenylimino)methyl]-3-methoxyphenol compound has been investigated with experimental (XRD, UV-vis and NMR) and theoretical (DFT and TD-DFT) methods. The results clearly show that structural preference of the compound is definitely depended on its state. Namely, the compound exists in phenol-imine form in the solid state while one or both of these forms can be seen in solvent media. For example, the compound prefers phenol-imine form in benzene while both forms exist in EtOH and DMSO solvents. Coexistence of two forms has been quantified with NMR studies, giving a ratio of 11:9 for phenol and keto structures of the compound in acetone-d6 solvent.

Keywords: Keto-amine; NMR; Phenol-imine; Schiff base; Tautomerism; X-ray.

Publication types

Research Support, Non-U.S. Gov't