Unimolecular gas-phase reactions of the methyl acetoacetate radical cation. Oxygen atom permutation via ion-molecule complexes |
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Authors: | Dorothe Berthomieu Jeanine Tortajada Jean-Pierre Morizur Henri-Edouard Audier |
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Institution: | Dorothée Berthomieu,Jeanine Tortajada,Jean-Pierre Morizur,Henri-Edouard Audier |
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Abstract: | The reactions of metastable decomposing methyl acetoacetate (a mixture of keto a ad enol tautomers) are reported and discussed. The unimolecular fragmentations of the tautomers are different. The metastable decomposing radical cation of the keto form displays four specific ions: M –CO]+˙, M – CH2O]+˙, M – CH2CO]+˙ and m/z 43. The results derived from D-, 13C- and 18O-labelled precursors together with thermochemical data have been used to study the mechanisms. Experimental results indicate that an unexpected isomerization occurs before dissociation. It formally corresponds to oxygen atom permutation of the two carbonyl groups without participation of the carbon atoms. This remarkable process is interpreted in terms of a mechanism involving ion-molecule complexes. |
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