Understanding the Mechanism of Base-Assisted Decomposition of (N-halo),N-alkylalcoholamines
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Understanding the Mechanism of Base-Assisted Decomposition of (N-halo),N-alkylalcoholaminesAutor(es)
Data
2003-09-29Cita bibliográfica
J. Andrés, X. L. Armesto, M. Canle L., M. V. García, D. R. Ramos and J. A. Santaballa, Understanding the mechanism of base-assisted decomposition of (N-halo),N-alkylalcoholamines, Org. Biomol. Chem., 2003, 1, 4323 DOI: 10.1039/B306076D
Resumo
[Abstract] The base-assisted decomposition of (N-X),N-methylethanolamine (X = Cl, Br) takes place mainly through two concurrent processes: a fragmentation and an intramolecular elimination. The global process follows second order kinetics, first order relative to both (N-X),N-methylethanolamine and base. Interaction of the base with the ionizable hydroxylic hydrogen triggers the reaction. The intramolecular elimination pathway leads to formaldehyde and 2-aminoethanol as reaction products via base-assisted proton transfer from the methyl to the partially unprotonated hydroxylic oxygen, with loss of halide. Meanwhile, the fragmentation pathway leads to methylamine and two equivalents of formaldehyde via bimolecular base-promoted concerted breakage of the molecule into formaldehyde, halide ion and N-methylmethanimine. Kinetic evidences allow a crude estimation of the concertedness and characterization of the transition structure for both processes, which are slightly asynchronous, the proton transfer to the base taking place ahead of the rest of the molecular events. The degree of asynchroneity increases as the bases become weaker. Electronic structure calculations, at the B3LYP/6-31++G** level, on the fragmentation pathway support the proposed mechanism.
Descrición
This document is the Accepted Manuscript version of a Published Work, after peer review and technical editing by the publisher. To access the final edited and published work see DOI https://doi.org/10.1039/B306076D
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© The Royal Society of Chemistry
ISSN
1477-0539