Effect of molecular structure on fragmentation of isolated organic molecules in solid rare gas matrices

The effect of excess energy on the primary radical cations of bifunctional carbonyl compounds and aliphatic alkynes was simulated by matrix isolation method using rare gas matrices with various ionization potentials. The formation of fragmentation products was monitored by EPR and FTIR spectroscopy....

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Bibliographic Details
Published in:Radiation physics and chemistry (Oxford, England : 1993) England : 1993), 2012-09, Vol.81 (9), p.1434-1439
Main Authors: Kobzarenko, A.V., Sukhov, F.F., Orlov, A.Yu, Kovalev, G.V., Baranova, I.A., Feldman, V.I.
Format: Article
Language:English
Subjects:
Alkynes
Bifunctional compounds
Cations
EPR spectroscopy
Fragmentation
FTIR spectroscopy
Mathematical analysis
Matrices
Matrix isolation
Matrix methods
Methyl radicals
Radical cations
Radicals
“Hot” fragmentation
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Summary:The effect of excess energy on the primary radical cations of bifunctional carbonyl compounds and aliphatic alkynes was simulated by matrix isolation method using rare gas matrices with various ionization potentials. The formation of fragmentation products was monitored by EPR and FTIR spectroscopy. It was shown that the radical cations of bifunctional compounds (CH3OCH2COCH3 and CH3COCOCH3) dissociated effectively yielding CH3 radicals upon irradiation in solid argon matrix at T≤16K. In addition to isolated methyl radicals, the radical pairs consisting of two methyl radicals separated by two CO molecules were detected in the case of diacetyl. The probability of fragmentation decreases with the decreasing excess energy by switching from Ar to Xe. In general, bifunctional molecules were found to be less stable to “hot” ionic fragmentation in low-temperature solids in comparison with simple prototype compounds. In the case of alkynes of the RCCH type, a noticeable yield of fragmentation products was observed when R=–C(CH3)3, but it was negligible for R=–CH3. The mechanisms of “hot” reactions and excess energy relaxation are discussed. ► Radiolysis of bifunctional organic compounds and alkynes. ► Dependence of “hot” fragmentation probability from molecular structure. ► Ions of bifunctional compounds are less stable than those of monofunctional ones. ► Alkynes are rather stable to “hot” fragmentation.
ISSN:0969-806X
1879-0895
DOI:10.1016/j.radphyschem.2012.01.004