Hydroxylamine as an Oxygen Nucleophile. Structure and Reactivity of Ammonia Oxide

Kirby, Anthony J.; Davies, John E.; Brandão, Tiago A. S.; Silva, Pedro F. da; Rocha, Willian R.; Nome, Faruk

doi:10.1021/ja065147q

Cited by 63 publications

(48 citation statements)

References 21 publications

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“…Reactions of the neutral form with phosphate esters typically result in the formation of the Ophosphorylated product, and probably involve the ammonia oxide tautomer NH 3 + -O -; 14 while at high pH the hydroxylamine anion is the most reactive α-effect nucleophile -and hence the most reactive of all nucleophiles towards phosphate phosphorus.…”

Section: Resultsmentioning

confidence: 99%

Reactions of alpha-nucleophiles with a model phosphate diester

Kirby¹,

Manfredi²,

Souza³

et al. 2008

Arkivoc

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We dedicate this paper to Prof. Harri Lönnberg on the occasion of his 60 th birthday, in recognition of his many lasting contributions to Bioorganic Chemistry. AbstractSubstantial rate enhancements are observed for the reactions of α-effect nucleophiles with 2,4-dinitrophenyl ethyl phosphate diester 4. The effect is largest (ca. 4500-fold) for the hydroperoxide anion. However, the most reactive α-effect nucleophile, and thus the most reactive nucleophile towards phosphate phosphorus at pHs near to or above its pK a of 13.74, is the hydroxylamine anion NH 2 O -. The kinetic reactivities of the α-effect nucleophiles follow aBrønsted correlation, with a slope β nuc = 0.41±0.03 greater than that (0.30) observed for non-α-effect nucleophiles, consistent with a thermodynamic origin for the effect.

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Section: Resultsmentioning

confidence: 99%

Reactions of alpha-nucleophiles with a model phosphate diester

Kirby¹,

Manfredi²,

Souza³

et al. 2008

Arkivoc

Self Cite

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“…However, recent reports have suggested the zwitterionic form, NH 3 O, is present in aqueous solution in significant proportions. 13,35,36 Therefore, it is possible that this interesting species plays an important role in the uncatalysed pathway. A full theoretical investigation of the mechanism involving the NH 3 O species requires a reliable evaluation of its stability by direct theoretical methods, which is beyond the scope of the present report.…”

Section: Discussionmentioning

confidence: 99%

“…[12][13][14] Pioneering studies on the mechanism of the hydroxylamine reaction with carboxylic esters have been reported by Jencks. 15, 16 This author observed that the reaction of hydroxylamine with p-nitrophenyl acetate in aqueous solution leads to O-acylhydroxylamine as the main product with a second order overall kinetics and first order for hydroxylamine. In addition, Jencks reported the hydroxylamine, combined with its protonated species, catalysed the reaction of O-acylhydroxylamine to form hydroxamic acid.…”

Section: Hydroxylamine Reactivity With Carboxylic Estersmentioning

confidence: 99%

Dual bifunctional catalysis and the α-effect in the reaction of hydroxylamine with phenylacetate

Mazera

Pliego

Almerindo

et al. 2011

J. Braz. Chem. Soc.

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A reação da hidroxilamina com acetato de fenila foi investigada teoricamente para se obter uma melhor compreensão do efeito alfa nas reações de nucleófilos neutros. Os cálculos foram feitos em nível B3LYP/6-311+G(2df,2p)//HF/6-31G(d) incluindo o solvente (água) em nível PCM/HF/6-31G(d). Os resultados mostram que um ataque direto da hidroxilamina leva a uma barreira de energia livre de ativação DG ‡ muito alta, em torno de 50 kcal mol -1. Uma segunda molécula de hidroxilamina pode catalisar o processo através de catálise bifuncional usando ambos os grupos NH 2 e OH simultaneamente. Esta catálise bifuncional reduz o DG ‡ para 19 kcal mol -1 e é capaz de explicar a relação de produtos cinético e termodinâmico observada experimentalmente.The reaction of hydroxylamine with phenyl acetate was theoretically investigated to shed light on the role of catalysis and the origin of the a-effect in this system. Calculations at the B3LYP/6-311+G(2df,2p)//HF/6-31G(d) level and the solvent effect included at the PCM/HF/6-31G(d) level predict that the direct attack of hydroxylamine to the carbonyl centre has a high DG ‡ barrier, close to 50 kcal mol -1. A second hydroxylamine molecule can catalyse the process through bifunctional catalysis using both the NH 2 and OH groups simultaneously. This dual bifunctional catalysis decreases the DG ‡ to 19 kcal mol -1 and is able to explain the experimentally observed kinetics and product ratio.

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“…Although 1z (Scheme 1) is not an α-effect nucleophile as usually defined, it is well suited to substitution reactions involving addition-intermediates, because proton transfer from the H 3 N + group to a developing negatively charged center, e.g., the oxygen of a C=O or P=O group in the substrate, becomes thermodynamically favorable as reaction proceeds (Scheme 1). 4 Proton transfer catalysis is important in many substitution reactions, contributing significant rate enhancements. A classical example is the hydrolysis of the aspirin (acetyl salicylic acid) monoanion, for which water attack is facilitated by intramolecular general base catalysis by the carboxylate group (Scheme 2).…”

Section: Methodsmentioning

confidence: 99%