Zinin reaction explained

Zinin reaction or Zinin reduction involves reduction of nitro aromatic compounds to the amines using sodium sulfide.^[1] It is used to convert nitrobenzenes to anilines.^{[2] [3]} The reaction selectively reduces nitro groups in the presence of other easily reduced functional groups (e.g., aryl halides and C=C bonds) are present in the molecule.

Reaction mechanism and example

The reaction requires water. Thiosulfate is one product. A possible stoichiometry for the reaction is:

4 ArNO₂   +   6 S^2-   + 7 H₂O → 4  ArNH₂   +   3 S₂O₃^2- + 6 OH^-Mechanistic studies have implicated a role for disulfide that is generated in situ. Nitrosobenzenes (ArNO) and phenylhydroxylamine (ArNHOH) are probable intermediates.

Dinitrobenzenes can often be reduced selectively to the nitroaniline. ^[4]

History

The reaction was discovered by a Russian organic chemist Nikolay Zinin (Russian: Николай Николаевич Зинин) (25 August 1812, Shusha – 18 February 1880, Saint Petersburg).

Notes and References

1. Porter . H. K. . The Zinin Reduction of Nitroarenes . 1973 . 20 . 4 . 455–481 . 10.1002/0471264180.or020.04 . Organic Reactions. 0471264180 .
2. Beschreibung einiger neuer organischer Basen, dargestellt durch die Einwirkung des Schwefelwasserstoffes auf Verbindungen der Kohlenwasserstoffe mit Untersalpetersäure . German . Description of some new organic bases, represented by the action of hydrogen sulphide on hydrocarbons with sub-nitric acid . N. . Zinin . Nikolay Zinin . . 27 . 1 . 140–153 . 1842 . 10.1002/prac.18420270125.
3. Über die Reduktion von Nitroverbindungen nach der Methode von Zinin . German . On the reduction of nitro compounds by the method of Zinin . Richard Willstätter, Heinrich Kubli . . 41 . 2 . 1936–1940 . 1908 . 10.1002/cber.19080410273.
4. The preferential reduction of 4,6 (5,7)-dinitro and 5,6-dinitrobenzimidazoles. Dyes and Pigments. 53. 3. 263–266. 2002. 10.1016/S0143-7208(02)00018-9. Sebla Dincer.