Elimination Reactions of (E)-2,4-Dinitrobenzaldehyde O-Aryloximes Promoted by RO-/ROH Buffers in EtOH

Elimination reactions of (E)-2,4-dinitrobenzaldehyde O-aryloximes 1−3 promoted by EtO-, PhC(CH3)NO-/PhC(CH3)NOH, and CF3CH2O-/CF3CH2OH buffers in ethanol have been studied kinetically. The reactions produced 2,4-dinitrobenzonitrile and aryloxides as the only products. The observed second-order kinetics, Brønsted β = 0.55−0.75, |βlg| = 0.39−0.48 are consistent with the E2 mechanism. The Brønsted β decreased as the leaving group was made more nucleofugic and the |βlg| increased with a weaker base. The result can be described by a positive interaction coefficient, pxy = ∂β/∂pK 1g = ∂β1g/∂pK BH > 0, which provides additional support for the E2 mechanism.