Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/195502
Type: Artigo de periódico
Title: The Kinetic Method As A Structural Diagnostic Tool: Ionized Alpha-diketones As Loosely One-electron Bonded Diacylium Ion Dimers.
Author: Meurer, Eduardo C
Gozzo, Fabio C
Augusti, R
Eberlin, Marcos N
Abstract: The kinetic method is used to corroborate the description of ground state ionized alpha-diketones as loosely electron-bonded acylium ion dimers: R(1)-C=O(+)---e(-)---(+)O=C-R(2). The abundance ratio of both the acylium ion fragments R(1)CO(+) and R(2)CO(+) (summed to those of their respective secondary fragments) formed upon low energy (5 eV) collision-induced dissociation of several ionized alpha-diketones is found to correlate linearly with the ionization energies (IEs) of the corresponding R(1)CO(.) and R(2)CO(.) free radicals as predicted by density functional theory calculations at the B3LYP/6-311++G(d,p) level. However, when these abundances are taken from 70 eV electron ionization mass spectra, lower and sometimes inverted ratios (2,3-pentanedione and 2,3-hexanedione) are observed. Inverted ratios are also observed via charge-exchange mass spectrometry/mass spectrometry (MS/MS) experiments for ionized 2,3-pentanodione formed with relatively high internal energies. Ionized alpha-diketones are found to display an effective temperature of 1705 K, which indicates an intermediate loosely-bonded nature. B3LYP/6-311++G(d,p) optimized geometries and charge and spin densities also corroborate the description of ground state ionized alpha-diketones as loosely electron-bonded diacylium ion dimers.
Citation: European Journal Of Mass Spectrometry (chichester, England). v. 9, n. 4, p. 295-304, 2003.
Rights: fechado
Identifier DOI: 10.1255/ejms.563
Address: http://www.ncbi.nlm.nih.gov/pubmed/12939482
Date Issue: 2003
Appears in Collections:Unicamp - Artigos e Outros Documentos

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