Full-text Article (Subscribers only)
Full-text article (257 kB)
(subscribers only)

Buy article on-line and get access immediately
Buy article on-line for £11.75
(get immediate access)

Search
Search

Go Back

Eur. J. Mass Spectrom. 9, 295 - 304 (2003)
DOI: 10.1255/ejms.563

The kinetic method as a structural diagnostic tool: ionized α-diketones as loosely one-electron bonded diacylium ion dimers

Eduardo C. Meurer,a Fabio C. Gozzo,a R. Augustib and Marcos N. Eberlin*a
aState University of Campinas UNICAMP, Institute of Chemistry CP6154, 13083-970 Campinas, SP Brazil. E-mail:
bFederal University of Minas Gerais UFMG, Department of Chemistry, CP 702, 31270-901 Belo Horizonte, MG Brazil

ABSTRACT:
The kinetic method is used to corroborate the description of ground state ionized α-diketones as loosely electron-bonded acylium ion dimers: R1C=O+---e---+O=CR2. The abundance ratio of both the acylium ion fragments R1CO+ and R2CO+ (summed to those of their respective secondary fragments) formed upon low energy (5 eV) collision-induced dissociation of several ionized α-diketones is found to correlate linearly with the ionization energies (IEs) of the corresponding R1CO· and R2CO· 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 α-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 α-diketones as loosely electron-bonded diacylium ion dimers.

Keywords:

You can now buy this paper on-line in PDF format; it costs only £11.75. Just click on the BUY on-line button. You can pay on-line through a secure server and get access immediately.


© IM Publications
Any problems? E-mail .
CrossRef Member