Bamberger rearrangement

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The Bamberger rearrangement is the chemical reaction of N-phenylhydroxylamines with strong aqueous acid, which will rearrange to give 4-aminophenols.[1][2][3] It is named for the German chemist Eugen Bamberger (1857–1932).

The Bamberger rearrangement

N-Phenylhydroxylamines are typically synthesized from nitrobenzenes by reduction using rhodium[4] or zinc.[5]

Reaction mechanism[edit]

The mechanism of the Bamberger rearrangement proceeds from the monoprotonation of N-phenylhydroxylamine 1. N-protonation 2 is favored, but unproductive. O-protonation 3 can form the nitrenium ion 4, which can react with nucleophiles (H2O) to form the desired 4-aminophenol 5.[6][7]

The mechanism of the Bamberger rearrangement

References[edit]

  1. ^ Bamberger, E. (1894). "Ueber die Reduction der Nitroverbindungen". Chemische Berichte 27 (2): 1347–1350. doi:10.1002/cber.18940270229. 
  2. ^ Bamberger, E. (1894). "Ueber das Phenylhydroxylamin". Chemische Berichte 27 (2): 1548–1557. doi:10.1002/cber.18940270276. 
  3. ^ Harman, R. E. (1955). "Chloro-p-benzoquinone" (PDF). Org. Synth. 35: 22. ; Coll. Vol. 4, p. 148 
  4. ^ Oxley, P. W.; Adger, B. M.; Sasse, M. J.; Forth, M. A. (1989). "N-Acetyl-N-phenylhydroxylamine via Catalytic Transfer Hydrogenation of Nitrobenzene using Hydrazine and Rhodium on Carbon" (PDF). Org. Synth. 67: 187. ; Coll. Vol. 8, p. 16 
  5. ^ Kamm, O. (1925). "β-Phenylhydroxylamine" (PDF). Org. Synth. 4: 57. ; Coll. Vol. 1, p. 445 
  6. ^ Sone, T.; Hamamoto, K.; Seiji, Y.; Shinkai, S.; Manabe, O. (1981). "Kinetics and Mechanisms of the Bamberger Rearrangement. Part 4. Rearrangement of Sterically Hindered Phenylhydroxylamines to 4-Aminophenols in Aqueous Sulphuric Acid Solution". Journal of the Chemical Society-Perkin Transactions II 1981 (2): 1596–1598. doi:10.1039/P29810000298. 
  7. ^ Kohnstam, G.; Petch, W. A.; Williams, D. L. H. (1984). "Kinetic Substituent and Isotope Effects in the Acid-Catalysed Rearrangement of N-Phenylhydroxylamines. Are Nitrenium Ions Involved?". Journal of the Chemical Society-Perkin Transactions II 1984 (3): 423–427. doi:10.1039/P29840000423. 

See also[edit]