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Type: Artigo de periódico
Title: The atmospheric pressure Meerwein reaction
Author: Meurer, EC
Eberlin, MN
Abstract: We have already shown that the in-vacuum gas-phase Meerwein reaction of (thio)acylium ions is general in nature and useful for class-selective screening of cyclic (thio)epoxides. Herein we report that this gas-phase reaction can also be performed efficiently at atmospheric pressure under both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) conditions. This alternative expands the range of molecules that can be reacted by gas-phase Meerwein reaction. Phenyl epoxide, thiirane, 3-methoxy-2,2-dimethyloxirane, propylene oxide, 2,2'-bioxirane, trans-1,3-diphenyl-2,3-epoxypropan-1-one, epichloridrine and propylene oxide are shown to react efficiently in both ESI and APCI conditions. Tetramethylurea (TMU) and (thio)TMU were both used as dopants, being co-injected with either toluene, acetonitrile or methanol solutions of the (thio)epoxides, with similar results. In both ESI and APCI, (thio)TMU is protonated preferentially, and these labile species dissociate promptly to yield (CH3)(2)N-C+=O and (CH3)(2)NCS+, which are the least acidic and most reactive (thio)acylium ions so far tested in the gas-phase Meerwein reaction. Under the low-energy ESI conditions set to favor both the formation of the (thio)acylium ion and ion/molecule reactions, (CH3)(2)NCO(S)(+) react competitively with (thio)TMU to form acylated (thio)TMU and with the (thio)epoxide to form the characteristic Meerwein products. Enhanced selectivity in structural characterization or for the screening of (thio)epoxides is achieved by performing on-line collision-induced dissociation of Meerwein products, particularly for the more structurally complex (thio)epoxides. Copyright (c) 2006 John Wiley & Sons, Ltd.
Subject: class-selective ion/molecule reactions
gaseous acylium ions
Meerwein reaction
ESI mass spectrometry
Country: Inglaterra
Editor: John Wiley & Sons Ltd
Citation: Journal Of Mass Spectrometry. John Wiley & Sons Ltd, v. 41, n. 4, n. 470, n. 476, 2006.
Rights: fechado
Identifier DOI: 10.1002/jms.1005
Date Issue: 2006
Appears in Collections:Unicamp - Artigos e Outros Documentos

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