Molecular structures of 2-methoxyphenol and 1,2-dimethoxybenzene as studied by gas-phase electron diffraction and quantum chemical calculations

• Published in: Journal of molecular structure 2009-09, Vol.933 (1), p.132-141
• Main Authors: Dorofeeva, Olga V., Shishkov, Igor F., Karasev, Nikolai M., Vilkov, Lev V., Oberhammer, Heinz
• Format: Article
• Language: English
• Subjects: 1,2-Dimethoxybenzene; 2-Methoxyphenol; Conformation; Gas-phase electron diffraction; Molecular structure; Quantum chemical calculations
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2009.06.009

The molecular structure and conformational properties of 2-methoxyphenol (2-MP) and 1,2-dimethoxybenzene (1,2-DMB) have been studied by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 methods with 6-31G(d,p) and cc-pVTZ basis sets). Of the three stable conformers predicted for 2-MP by quantum chemical calculations, the lowest energy form possesses a planar structure with an intramolecular hydrogen bond between phenolic hydrogen and methoxy oxygen ( anti–syn conformer of C s symmetry). The calculated concentration of this conformer is about 99% and this is confirmed by the GED data. Quantum chemical calculations predict three stable conformers for 1,2-DMB: anti–anti ( C 2v symmetry), anti–gauche ( C 1 symmetry), and gauche–gauche ( C 2 symmetry). The GED data were well reproduced for the mixture of these conformers with the relative abundance of 50 ± 12%, 36 ± 16%, and 14%, respectively. A similarly good agreement is also obtained for the single anti–gauche conformer. The experimental structural parameters agree well with results of B3LYP/cc-pVTZ calculations.