Detection of tautomer proportions of dimedone in solution: a new approach based on theoretical and FT-IR viewpoint.
Molecular structures of stable tautomers of dimedone [5,5-dimethyl-cyclohexane-1,3-dione and 3-hydroxy-5,5-dimethylcyclohex-2-enone] were optimized and vibrational frequencies were calculated in five different organic solvents (dimethylsulfoxide, methanol, acetonitrile, dichloromethane and chloroform). Geometry optimizations and harmonic vibrational frequency calculations were performed at DFT 6-31+G(d,p), DFT 6-311++G(2d,2p), MP2 6-311++G (2d,2p) and MP2 aug-cc-pVDZ levels for both stable forms of dimedone. Experimental FT-IR spectra of dimedone have also been recorded in the same solvents. A new approach was developed in order to determine tautomers' ratio using both experimental and theoretical data in Lambert-Beer equation. Obtained results were compared with experimental results published in literature. It has been concluded that while DFT 6-31+G(d,p) method provides accurate enol ratio in DMSO, MeOH, and DCM, in order to obtain accurate results for the other solvents the MP2 aug-cc-pVDZ level calculations should be used for CH₃CN and CHCl₃ solutions.
Department of Chemistry, Faculty of Science and Literature, Balikesir University, Balıkesir, Turkey, sedatk@balikesir.edu.tr.
Sedat
S
Karabulut
Hilmi
H
Namli
Jerzy
J
Leszczynski
D003512:Cyclohexanones / Q000737:chemistry*; D008958:Models, Molecular; D011789:Quantum Theory; D012996:Solutions; D012997:Solvents; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
D003512:Cyclohexanones; D012996:Solutions; D012997:Solvents; C004774:dimedone