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^-/CF₃CH₃OH 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, |β_1g| = 0.39-0.48 are consistent with the E2 mechanism. The Brønsted β decreased as the leaving group was made more nucleofugic and the |β_1g| increased with a weaker base. The result can be described by a positive interaction coefficient, p_xy = ∂β/∂pK_1g = ∂β_1g/∂pK_BH > 0, which provides additional support for the E2 mechanism.