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Type: Artigo de periódico
Title: Cyclization Reactions Of Acylium And Thioacylium Ions With Isocyanates And Isothiocyanates: Gas Phase Synthesis Of 3,4-dihydro-2,4-dioxo-2h-1,3,5-oxadiazinium Ions.
Author: Meurer, Eduardo C
Sparrapan, Regina
Tomazela, Daniela M
Eberlin, Marcos N
Augusti, Rodinei
Abstract: Gas-phase reactions of several acylium and thioacylium ions, that is H2C=N-C+=O, H2C=N-C+=S, O=C=N-C+=O, S=C=N-C+=O, H3C-C+=O, and (CH3)2N-C+=O, with both a model isocyanate and isothiocyanate, that is, C2H5-N=C=O and C2H5-N=C=S, were investigated using tandem-in-space pentaquadrupole mass spectrometry. In these reactions, the formation of mono- and double-addition products is observed concurrently with proton transfer products. The double-addition products are far more favored in reactions with ethyl isocyanate, whereas the reactions with ethyl isothiocyanate form, preferentially, either the mono-addition product or proton transfer products, or both. Retro-addition dominates the low-energy collision-induced dissociation of the mono- and double-addition products with reformation of the corresponding reactant ions. Ab initio calculations at Becke3LYP//6-311 + G(d,p) level indicate that cyclization is favored for the double-addition products and that products equivalent to those synthesized in solution, that is, of 3,4-dihydro-2,4-dioxo-2H-1,3,5-oxadiazinium ions and sulfur analogs, are formed.
Subject: Acetals
Phase Transition
Spectrometry, Mass, Matrix-assisted Laser Desorption-ionization
Citation: Journal Of The American Society For Mass Spectrometry. v. 16, n. 10, p. 1602-7, 2005-Oct.
Rights: fechado
Identifier DOI: 10.1016/j.jasms.2005.05.011
Date Issue: 2005
Appears in Collections:Unicamp - Artigos e Outros Documentos

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