File:Bamberger rearrangement mechanism v1.svg. From Wikimedia Commons, the free media repository. Download as PDF; Tools. What links here; Related changes. Bamberger rearrangement of phenylhydroxylamine (PHA) to para-aminophenol (PAP) is investigated at 353 K, with water as solvent, on a series of solid acid catalysts. The Bamberger rearrangement is the chemical reaction of N-phenylhydroxylamines with strong aqueous acid. ^ Bamberger, E. Bamberger rearrangement of phenylhydroxylamine (PHA) to para-aminophenol (PAP) is investigated at 353 K, with water as solvent, on a series of solid acid catalysts. Mississippi Department Corrections Early Release Program on this page.
Presto Mr Photo For Windows 7. 3-Hydroxylaminophenol mutase from Ralstonia eutropha JMP134 is involved in the degradative pathway of 3-nitrophenol, in which it catalyzes the conversion of 3-hydroxylaminophenol to aminohydroquinone. To show that the reaction was really catalyzed by a single enzyme without the release of intermediates, the corresponding protein was purified to apparent homogeneity from an extract of cells grown on 3-nitrophenol as the nitrogen source and succinate as the carbon and energy source.
3-Hydroxylaminophenol mutase appears to be a relatively hydrophobic but soluble and colorless protein consisting of a single 62-kDa polypeptide. The pI was determined to be at pH 4.5. In a database search, the NH 2-terminal amino acid sequence of the undigested protein and of two internal sequences of 3-hydroxylaminophenol mutase were found to be most similar to those of glutamine synthetases from different species. Hydroxylaminobenzene, 4-hydroxylaminotoluene, and 2-chloro-5-hydroxylaminophenol, but not 4-hydroxylaminobenzoate, can also serve as substrates for the enzyme. The enzyme requires no oxygen or added cofactors for its reaction, which suggests an enzymatic mechanism analogous to the acid-catalyzed Bamberger rearrangement. The recognition that synthetic nitroaromatic compounds are environmental hazards has led to a considerable amount of research on their biodegradation (for reviews, see references,,,, and ). Descargar Libreoffice-l10n-es.
As a result, a variety of novel enzymatic mechanisms for the degradation or transformation of nitroarenes have been discovered. Oxidative elimination of the nitro group as nitrite seems to be a key reaction in the catabolism of many mononitroaromatic and some dinitroaromatic compounds ().
In general, the electron-withdrawing character of the nitro group favors biological reduction, giving rise to ring hydrogenation (,,, ) or transformation of the nitro group to either nitroso, hydroxylamino, or amino derivatives (, ). Each of these products can be subjected to further transformation or mineralization (). Recent evidence suggests that the hydroxylaminoaromatic compounds are key intermediates in a variety of metabolic pathways of mononitroaromatic compounds. For example, an enzymatic rearrangement of aromatic hydroxylamines and hydroxamic acids to their corresponding ortho-aminophenol derivatives was observed in rabbit liver () and rat liver homogenates (). In the latter report, a hepatic isomerase-catalyzed mechanism that corresponded to the acid-catalyzed chemical reaction formerly described by Bamberger was proposed ().