Dediazoniation of Mono-substituted Benzenediazonium Tetrafluoroborate in Aqueous Solution at pH 1-7

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  • 芳香族ジアゾニウム塩の水溶液(pH1～7)中における分解反
  • 芳香族ジアゾニウム塩の分解反応に関する研究　Ｉ　　芳香族ジアゾニウム塩の水溶液（ｐＨ１〜７）中における分解反応

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Description

The dediazoniation of substituted (m-or p-) benzenediazonium tetrafluoroborate (R-C6H4-N2BF4, R=H, Me, MeO, Cl, Br, NO2, COOR' and OPh) in aqueous solutions (pH 1-7) was studied kinetically. The concentrations of diazonium salts were determined by measuring the concentration of the azo compound formed by NW acid colorimetrically. The main products of the dediazoniation were phenols and phenylazophenols. The decomposition rate is of first order with respect to the concentration of the diazonium salt and the rate constants ( k ) are markedly dependent on the pH values of the medium: at lower pH the values of k are constant, but above a certain value of pH it increases with pH linerly. These results were explained in terms of the equilibriums between diazonium ion and diazotate, ArN2+ ↔ ArN2OH ↔ArN2O- and it was concluded that the values of observed k at lower pH is the rate const ant of the dediazoniation of diazonium ion. The values of k depend also on the substituents. Hammett's relation between log k and σ is set up linerly for meta and several para (CN, NO2and COOEt) substituents whereas for other para substituents some scatter from the linearity is found. The scatter was reduced by using σ1+1.8|σR| instead of σ in plotting. This deviation was explained in terms of the resonance electron donability of the substituent and the stabiliza tion of the initial state.

Journal

  • NIPPON KAGAKU KAISHI

    NIPPON KAGAKU KAISHI 1976 (6), 968-972, 1976-06-10

    The Chemical Society of Japan

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