title: Major mechanistic differences between the reactions of hydroxylamine with phosphate di- and tri-esters.
abstract: Hydroxylamine reacts as an oxygen nucleophile, most likely via its ammonia oxide tautomer, towards both phosphate di- and triesters of 2-hydroxypyridine. But the reactions are very different. The product of the two-step reaction with the triester TPP is trapped by the NH2OH present in solution to generate diimide, identified from its expected disproportionation and trapping products. The reaction with H3N(+)-O(-) shows general base catalysis, which calculations show is involved in the breakdown of the phosphorane addition-intermediate of a two-step reaction. The reactivity of the diester anion DPP(-) is controlled by its more basic pyridyl N. Hydroxylamine reacts preferentially with the substrate zwitterion DPP(±) to displace first one then a second 2-pyridone, in concerted S(N)2(P) reactions, forming O-phosphorylated products which are readily hydrolysed to inorganic phosphate. The suggested mechanisms are tested and supported by extensive theoretical calculations.
authors.affiliation: Instituto Nacional de Ciência e Tecnologia de Catálise, Departamento de Química, Universidade Federal de Santa Catarina, CEP 88040-900, Florianópolis, Santa Catarina, Brazil.
authors.forename: Michelle
authors.initials: M
authors.lastname: Medeiros
authors.forename: Eduardo H
authors.initials: EH
authors.lastname: Wanderlind
authors.forename: José R
authors.initials: JR
authors.lastname: Mora
authors.forename: Raphaell
authors.initials: R
authors.lastname: Moreira
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Kirby
authors.forename: Faruk
authors.initials: F
authors.lastname: Nome
mesh_terms: D004952:Esters / Q000737:chemistry*; D006571:Heterocyclic Compounds / Q000737:chemistry; D019811:Hydroxylamine / Q000737:chemistry*; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
chemical_list: D004952:Esters; D006571:Heterocyclic Compounds; D009943:Organophosphorus Compounds; D010710:Phosphates; C528765:tris(o-phenylenedioxy)cyclotriphosphazene; D014867:Water; D019811:Hydroxylamine