关键词: 丙酮肟, ¹H NMR, 混合溶剂, 溶剂化作用, 化学位移

Abstract: ~1H NMR spectra of acetoxime have been measured as a function of the mole fraction of certain aromatic hydrocarbons in mixed solvent of CCl_4 and benzene or toluene. It has been found that the chemical shifts of the two methyl groups in acetoxime and of benzene or toluene move upfield gradually in the mixed solvent as the mole fraction of aromatic component increases. The moving rate of the resonance absorption line of the two methyl groups in acetoxime are different. The △δ of β-CH_3 is larger than that of α-CH_3. The absorption line of the two methyl groups is a singlet in CCl_4 and splits to a doublet when the concentration of benzene or toluene in the solvent is higher than 30% (mole/mole). The experimental results also show that the extent of upfield shifts of either the methyl groups in acetoxime or the aromatic hydrogens are reduced when a hydrogen of benzene is substituted by methyl group. All of the chemical shifts can be correlated with a linear equation as δ=A+Bx, Where, x is the mole fraction of benzene or toluene in the mixed solvent. The correlation coefficients R are approximately equal to -1.

Key words: Acetoxime, ¹H NMR, Mixed solvent, Solvation, Chemical shifts