The Hofmann Rearrangement. I. Kinetic Substituent Effects of <I>ortho</I>-, <I>meta</I>-, and <I>para</I>-Substituted <I>N</I>-Bromobenzamides

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概要

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• The kinetic substituent effects on the Hofmann rearrangements of <I>ortho</I>-, <I>meta</I>-, and <I>para</I>-substituted <I>N</I>-bromobenzamides were studied in an aqueous sodium hydroxide solution. The rate constants of the <I>meta</I>- and <I>para</I>-derivatives were correlated by means of our equation:<BR>log<I>k</I>⁄<I>k</I><SUB>0</SUB>=−2.39(σ<SUP>0</SUP>+0.41<I>Δ</I>\barσ<SUB>R</SUB><SUP>+</SUP>)+0.002<BR>The reaction rates of <I>ortho</I>-derivatives were found to be 2–20 times faster than those of the corresponding <I>para</I>-derivatives. The reaction mechanism of this rearrangement was discussed in terms of LFER, the <I>ortho</I>/<I>para</I> rate ratios, and the activation parameters; as a result, the concerted mechanism (the participation of the phenyl group in electron-deficient nitrogen at the transition state) was favored rather than the two-step mechanism. The similarity of the reaction mechanism of the Hofmann to the Lossen rearrangement was also shown on the basis of LFER.

• 公益社団法人 日本化学会の論文

著者

• TSUNO Yuho

  The Institute for Fundamental Research of Organic Chemistry, Kyushu University

• Imamoto Tsuneo

  The Institute of Scientific and Industrial Research, Osaka University

• Yukawa Yasuhide

  The Institute of Scientific and Industrial Research, Osaka University

• Imamoto Tsuneo

  The Institute of Scientific and Industrial Research, Osaka Univervity

• Yukawa Yasuhide

  The Institute of Scientific and Industrial Research, Osaka Univervity

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