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The Mechanism of Dephosphorylation of Bis(2,4-dinitrophenyl) Phosphate in Mixed Micelles of Cationic Surfactants and Lauryl Hydroxamic Acid

2009; American Chemical Society; Volume: 74; Issue: 21 Linguagem: Inglês

10.1021/jo9017638

1520-6904

Marcelo Silva, Renata Mello Giona, Muhammad Akhyar Farrukh, Janio Venturini, Clifford A. Bunton, Humberto M. S. Milagre, Marcos N. Eberlin, Haidi D. Fiedler, Faruk Nome,

Analytical Chemistry and Chromatography

Mixed micelles of cetyltrimethylammonium bromide (CTABr) or dodecyltrimethylammonium bromide (DTABr) and the α-nucleophile, lauryl hydroxamic acid (LHA) accelerate dephosphorylation of bis(2,4-dinitrophenyl)phosphate (BDNPP) over the pH range 4−10. With a 0.1 mole fraction of LHA in DTABr or CTABr, dephosphorylation of BDNPP is approximately 104-fold faster than its spontaneous hydrolysis, and monoanionic LHA− is the reactive species. The results are consistent with a mechanism involving concurrent nucleophilic attack by hydroxamate ion (i) on the aromatic carbon, giving an intermediate that decomposes to undecylamine and 2,4-dinitrophenol, and (ii) at phosphorus, giving an unstable intermediate that undergoes a Lossen rearrangement yielding a series of derivatives including N,N-dialkylurea, undecylamine, undecyl isocyanate, and carbamyl hydroxamate.