Kinetics and mechanisms of the Bamberger rearrangement. Part 4. Rearrangement of sterically hindered phenylhydroxylamines to 4-aminophenols in aqueous sulphuric acid solution

Sone, Takaaki; Hamamoto, Kazuhiro; SEIJI, Y.; Shinkai, Seiji; Manabe, Osamu

doi:10.1039/p29810001596

Cited by 26 publications

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“…The experimental data, product yields as a function of [NaCl] or [NaBr , are provided in Tables S1-S8 as supplementary material> The following provides a brief description of the pertinent results with each hydroxylamine. N-(2,6-Dimethylpheny1)hydroxylamine (8) With chloride ion present, two products were observed, 4-amino-3,5-dimethylphenol (10) and 4-chloro-2,6-dimethylaniline (15). Rate constants were measured in a set of solutions containing 0.000324 M HC104, ionic strength = 1 M, by following a change in optical density at 280 nm in the UV absorbance spectra.…”

Section: Resultsmentioning

confidence: 99%

“…The N-arylhydroxylamines were prepared from the corresponding nitroarenes by zinc reduction in methano1:water containing ammonium chloride, followed by recrystallization from benzene:petroleum ether (7,8). Products were commercially available or were obtained from catalytic hydrogenation of the appropriate nitro compound.…”

Section: Methodsmentioning

confidence: 99%

“…Product identifications were verified by spiking the reaction mixtures with authentic samples. Rate constants were measured as previously described (7)(8)(9), by following the change in optical density at an appropriate wavelength in the UV.…”

Section: Methodsmentioning

confidence: 99%

“…This same study also showed that there was no exchange of 180 into unreacted starting material, establishing that N-0 bond fission is not reversible (5) (although a similar study with N-1-naphthylhydroxylamine (6) suggests that this is not always the case). Detailed kinetic studies showed that the reaction was first order in phenylhydroxylamine and first order in H+ to pH 1-2, with the rate then becoming independent of acidity to acids with Ho of about -1, at which point the rate began to increase again (7)(8)(9). Spectral measurements suggested that the initial levelling was associated with protona?con to the unreactive N-protonated hydroxylamine 7, with p~a N = 1.90 for the parent system (7,9).…”

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confidence: 97%

“…The occurrence of an SN1-type mechanism leading to an arylnitrenium ion as an intermediate was suggested by several pieces of evidence, including solvent isotope effects (9) and entropies of activation (7,8) in addition to the previously mentioned experiment in HC1 by the Ingold group (3). Substituents in the aromatic ring have a significant effect, with large negative p values consistent with the development of considerable positive charge in the ring in the transition state for the reaction.…”

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Halide ion trapping of nitrenium ions formed in the Bamberger rearrangement of N-arylhydroxylamines. Lifetime of the parent phenylnitrenium ion in water

Fishbein¹,

McClelland²

1996

Can. J. Chem.

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The acid reactions of five arylhydroxylamines (Ar = 2,6-Me2C6H3, 2,5-Me2C6H3, 2-MeC6H4, 2-C1C6H4, and C6H5) have been studied at constant ionic strength (NaC104) in the presence of varying amounts of NaBr and NaCI. Each system resulted in the corresponding p-aminophenol, the product of Bamberger rearrangement, as the only detectable product in the absence of halide. ' The addition of halide ion reduced the yield of this product, with the appearance of the corresponding p-haloaniline, o-haloaniline (where appropriate), and the parent aniline (predominantly with bromide). Rate constants for the reaction were measured in the case of the parent and 2,6-dimethyl systems and showed small decreases (chloride) or increases (bromide) with increasing halide concentration. These changes did not correlate with the change in products, implying that the rate variations were caused by specific salt effects. Product data were analyzed by a mechanism involving rate-limiting formation of the appropriate arylnitrenium ion followed by product-determining steps involving trapping by the solvent or by the added halide. The possibility that a portion of the halide-trapped products were derived from a pre-association mechanism was also included. Kinetic analyses then produced kBr:kw and kcl:kw ratios for two limiting cases, one involving pre-association with an equilibrium constant K,, = 0.3, and one ignoring pre-association. From an azide:water ratio (kAz:kw) previously determined for the 2,6-dimethylphenylnitrenium, kBr was concluded to lie in the range (4-5) x lo9 M-I s-I for all of the nitrenium ions of this study. This range for kB, then led to k, values of (1-2) x lo9 s-I (2.5-Me2), (2-3) x 10' s-' (2-Me), and (4-8) x lo9 s-' (parent and 2-Cl), where the ranges reflect uncertainties in the exact value of kBr and in the contribution from pre-association. The lifetime of the parent phenylnitrenium ion in water at one molar ionic strength is concluded to lie in the range 125-250 ps.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 97%

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confidence: 99%

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Halide ion trapping of nitrenium ions formed in the Bamberger rearrangement of N-arylhydroxylamines. Lifetime of the parent phenylnitrenium ion in water

Fishbein¹,

McClelland²

1996

Can. J. Chem.

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Bamberger Rearrangement

2010

Comprehensive Organic Name Reactions and Reagents

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Intermolecular rearrangement of N ‐phenylhydroxylamines in acidic aqueous solution to afford the corresponding 4‐aminophenols, e.g., in aqueous sulfuric acid, is generally referred to as the Bamberger rearrangement. It has been reported that in this rearrangement the hydroxyl group is introduced into the aromatic ring via a nucleophilic attack of a hydrosulfate ion on the anilenium ion, which is generated by the heterolytic N‐O bond cleavage of O ‐protonated N ‐phenylhydroxylamine. It has been found that alkoxy, halogen, phenoxy are incorporated into the aromatic ring when the rearrangement of N‐phenylhydroxylamine is carried out in nucleophilic solvents.

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Rearrangement Reactions Involving the Amino, Nitro and Nitroso Groups

Williams

2009

Patai's Chemistry of Functional Groups

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Introduction Rearrangement of Hydrazobenzenes (The Benzidine Rearrangement) Rearrangement of Azoxybenzenes (The Wallach Rearrangement) Rearrangement Involving Phenylhydroxylamines Rearrangement of N ‐Halo Compounds Rearrangement Involving Nitro Groups Rearrangement Involving Nitroso Groups

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Kinetics and mechanisms of the Bamberger rearrangement. Part 4. Rearrangement of sterically hindered phenylhydroxylamines to 4-aminophenols in aqueous sulphuric acid solution

Cited by 26 publications

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Halide ion trapping of nitrenium ions formed in the Bamberger rearrangement of N-arylhydroxylamines. Lifetime of the parent phenylnitrenium ion in water

Halide ion trapping of nitrenium ions formed in the Bamberger rearrangement of N-arylhydroxylamines. Lifetime of the parent phenylnitrenium ion in water

Bamberger Rearrangement

Rearrangement Reactions Involving the Amino, Nitro and Nitroso Groups

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