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Type: Artigo de periódico
Title: Dehydrobenzoyl cations: Distonic ions with dual free radical and acylium ion reactivity
Author: Moraes, LAB
Eberlin, MN
Abstract: In the gas phase, m- and p-dehydrobenzoyl cations display strong duality of chemical behavior. The ions react selectively as either free radicals or acylium ions, depending on the choice of the neutral reaction partner. Transacetalization with 2-methyl-1,3-dioxolane, ketalization with 2-methoxyethanol, and epoxide ring expansion with epichlorohydrin demonstrate their acylium ion reactivity, whereas (SCH3)-S-. abstraction with dimethyl disulfide demonstrates their free radical reactivity. In one-pot reactions with gaseous mixtures of epichlorohydrin and dimethyl disulfide, the m- and p-dehydrobenzoyl cations react selectively at either site to form the two monoderivatized ions in variable but controlled yields; further reaction at either the remaining radical or the acylium charge site forms a single biderivatized ion as the final product. The o-dehydrobenzoyl cation also displays the expected radical and acylium ion reactivities. But for the ortho isomer, binding of the nucleophilic neutral to the free or derivatized C+=O group facilitates reactions at the radical site. Hence, the ortho isomer displays a unique behavior; its acylium ion reactions either occur simultaneously with, or are followed by, H-abstraction radical reactions. As shown by ab initio calculations, the three isomers display sigma-localized odd-spin and pi-delocalized charge densities, which characterize distonic structures with molecular orbital-separated radical and charge sites. The dehydrobenzoyl cations are also, according to the calculations, the most stable among 19 of the most feasible C7H4O+. isomers.
Country: EUA
Editor: Amer Chemical Soc
Citation: Journal Of The American Chemical Society. Amer Chemical Soc, v. 120, n. 43, n. 11136, n. 11143, 1998.
Rights: fechado
Identifier DOI: 10.1021/ja981152l
Date Issue: 1998
Appears in Collections:Unicamp - Artigos e Outros Documentos

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