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. 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.
Read more about this topic: Zincke Reaction
Famous quotes containing the words reaction and/or mechanism:
“An actor must communicate his author’s given message—comedy, tragedy, serio- comedy; then comes his unique moment, as he is confronted by the looked-for, yet at times unexpected, reaction of the audience. This split second is his; he is in command of his medium; the effect vanishes into thin air; but that moment has a power all its own and, like power in any form, is stimulating and alluring.”
—Eleanor Robson Belmont (1878–1979)
“When one of us dies of cancer, loses her mind, or commits suicide, we must not blame her for her inability to survive an ongoing political mechanism bent on the destruction of that human being. Sanity remains defined simply by the ability to cope with insane conditions.”
—Ana Castillo (b. 1953)