Eliminations from (E)-O-Arylbenzaldehyde Oximes Promoted by Hydroxide in 60 percent aq. Dimethyl Sulphoxide. Mechanism and Transition-state Characteristics of Nitrile-forming Eliminations

Article abstract of DOI:10.1039/P29890000489

Reactions of the (E)-O-arylbenzaldehyde oximes (1; Ar = 2,4-dinitrophenyl), (2; Ar = p-nitrophenyl), and (3; Ar = phenyl) with OH^- in 60 percent aq.DMSO have been investigated.The eliminations are quantitative, producing only benzonitriles and aryloxides.The observation of second-order kinetics, K₂^OD-/k₂^OH- = 1.15 - 1.84, and β_lg = -0.59 is consistent with an E2 mechanism.The Hammett ρ and k₂^OD-/k₂^OH- values increased with poorer leaving groups.For a given substrate the k₂^OD-/k₂^OH- value remained (within experimental error) roughly constant, in spite of changes in the β-aryl substituents.These changes in transition state parameters can be interpreted in term of the differing nitrile-forming transition states involved.

Full text of DOI:10.1039/P29890000489

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