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KMID : 1059519930370010148
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Journal of the Korean Chemical Society
1993 Volume.37 No. 1 p.148 ~ p.153
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Substituent Effects on the Wallach Rearrangement of 4'-Halogenated Azoxybenzenes in Conc. Sulfuric Acid : Reaction Mechanism and Linear Free Energy Relationship
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Keum Sam-Rok
Lee Hyo-Il
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Abstract
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The Wallach rearrangement of 4'-halogenated azoxybenzenes in strong sulfuric acid was reinvestigated by UV-Vis spectrophotometric method. Interestingly an excellent linearity (logkobs = -0.61 σR+ -3.29, γ = 0.998) was obtained on plotting log (rate) vs. substituent constant, σR+, which is known as the Pi delocalization parameter. Thus B-H mechanism via a charged intermediate (DC++), which can be largely stabilized by resonance, is far more favored for the Wallach rearrangement.
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