Solvent Effect on the Conformation of 2,6-Dimethoxyphenol Simulated with MOPAC2000

Mikiji SHIGEMATSUa*, Takayuki KOBAYASHIb, Kouzou YOSHITANIa and Mitsuhiko TANAHASHIa

aFaculty of Agriculture, Gifu University
Gifu 501-1193, Japan
bThe United Graduate School of Agricultural Science, Gifu University
Gifu 501-1193, Japan

(Received: May 24, 2002; Accepted for publication: November 15, 2002; Published on Web: December 6, 2002)

The conformation of 2,6-dimethoxyphenol (DMP), especially the solvent effect on the intra-molecular hydrogen bond was computed with semi-empirical molecular orbital calculation, MOPAC2000. In non-polar solvents (gaseous phase and benzene), the phenolic hydrogen oriented toward one of the methoxyl oxygens via an intra-molecular hydrogen bond. In polar solvents (chloroform, acetone and water), the phenolic hydroxyl group was sited between two methoxyl oxygens with balance of weak hydrogen bonds to them. This solvent effect on the optimum conformation was similar to guaiacol analyzed previously, and would be due to the split of the intra-molecular hydrogen bond caused by interaction from polar solvents. The rotational flexibilities of the hydroxyl and two methoxyl groups of DMP were high, because many of the low energy conformations were detected near the optimum conformation. The flexibilities of two methoxyl groups were lower in water than in gaseous phase. The cause may be complex interaction produced by polar solvents to the balance of intra-molecular hydrogen bonds among hydroxyl group and two methoxyl groups.

Keywords: 2,6-Dimethoxyphenol, Optimum conformation, Solvent effect, Hydrogen bond, Methoxyl group, Phenolic hydroxyl group

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