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The Zincke reaction is an organic reaction in which a pyridine is transformed into a pyridinium salt by reaction with 2,4-dinitro-chlorobenzene and a primary amine, named after Theodor Zincke. The Zincke reaction should not be confused with the Zincke-Suhl reaction or the Zincke nitration. Furthermore, the Zincke reaction has nothing to do with the chemical element zinc. ==Reaction mechanism== The first reaction is the formation of the ''N''-2,4-dinitrophenyl-pyridinium salt (2). This salt is typically isolated and purified by recrystallization. Upon heating a primary amine with the ''N''-2,4-dinitrophenyl-pyridinium salt (2), the addition of the amine leads to the opening of the pyridinium ring. A second addition of amine leads to the displacement of 2,4-dinitroaniline (5) and formation of the König salt (6a and 6b). The trans-cis-trans isomer of the König salt (6a) can react by either sigmatropic rearrangement or nucleophilic addition of a zwitterionic intermediate to give cyclized intermediate (7). This has been suggested to be the rate-determining step.〔Marvell, E. N.; Caple, G.; Shahidi, I. ''J. Am. Chem. Soc.'' 1970, ''92'', 5641-5645. ()〕〔Marvell, E. N.; Shahidi, I. ''J. Am. Chem. Soc.'' 1970, ''92'', 5646-5649. ()〕 After proton transfer and amine elimination, the desired pyridinium ion (9) is formed. This mechanism can be referred to as an instance of the ANRORC mechanism: nucleophilic addition (AN), ring opening and ring closing. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Zincke reaction」の詳細全文を読む スポンサード リンク
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