Locating the charge site in heteroaromatic cations

dc.creatorCarvalho, M
dc.creatorGozzo, FC
dc.creatorMendes, MA
dc.creatorSparrapan, R
dc.creatorKascheres, C
dc.creatorEberlin, MN
dc.date1998
dc.dateJUL
dc.date2014-12-02T16:25:13Z
dc.date2015-11-26T17:21:21Z
dc.date2014-12-02T16:25:13Z
dc.date2015-11-26T17:21:21Z
dc.date.accessioned2018-03-29T00:08:51Z
dc.date.available2018-03-29T00:08:51Z
dc.identifierChemistry-a European Journal. Wiley-v C H Verlag Gmbh, v. 4, n. 7, n. 1161, n. 1168, 1998.
dc.identifier0947-6539
dc.identifierWOS:000074987000005
dc.identifier10.1002/(SICI)1521-3765(19980710)4:7<1161
dc.identifierhttp://www.repositorio.unicamp.br/jspui/handle/REPOSIP/81294
dc.identifierhttp://www.repositorio.unicamp.br/handle/REPOSIP/81294
dc.identifierhttp://repositorio.unicamp.br/jspui/handle/REPOSIP/81294
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/1283346
dc.descriptionLow-energy collision-induced dissociation (CID) and ion-molecule reactions with 2-methyl-1,3-dioxolane (MD) performed by pentaquadrupole (QqQqQ) mass spectrometry were applied to locate the charge site in isomeric heteroaromatic cations. The 2-, 3-, and 4-pyridyl cations are indistinguishable by CID. However, as suggest ed by MS3 experiments and ab initio calculations, the 2-pyridyl cation reacts extensively with MD by a transacetalization-like mechanism to afford a bicyclic dihydrooxazolopyridyl cation. The 3- and 4-pyridyl cations, on the contrary react predominantly with MD by proton transfer, as does the analogous phenyl cation. The 2-. 4-, and 5-pyrimidyl cations display characteristic CID behavior. In addition, the 2-pyrimidyl cation reacts extensively with MD by the transacetalization-like mechanism, whereas proton transfer occurs predominantly for the 4- and 5-pyrimidyl cations. The ions thought to be the 2- and 3-furanyl and 2- and 3-thiophenyl cations show indistinguishable CID and ion-molecule behavior. This is most likely the result of their inherent instability in the gas phase and their spontaneous isomerization to the corresponding butynoyl and butynethioyl cations HC=CHCH2C=O+ and HC=CHCH2C=S+. These isomerizations, which are considerably exothermic according to G2(MP2) ab initio calculations, are indicated by a series of experimental results. The ions dissociate upon CID by loss of CO or CS and undergo transacetalization with MD. Most informative is the participation of HC=CHCH2C=S+ in a transacetalization/dissociation sequence with replacement of sulfur by oxygen, which is structurally diagnostic for thioacylium ions. It is therefore possible to locate the charge site of the 2-pyridyl and the three 2-, 4-, and 5-pyrimidyl cations and to identify the isomeric precursors from which they are derived. However, rapid isomerization to the common HC=CHCH2-C=O(S)(+) ion eliminates characteristic chemical behavior that could result from different charge locations in the heteroaromatic 2- and 3-furanyl and 2- and 3-thiophenyl cations.
dc.description4
dc.description7
dc.description1161
dc.description1168
dc.languageen
dc.publisherWiley-v C H Verlag Gmbh
dc.publisherBerlin
dc.publisherAlemanha
dc.relationChemistry-a European Journal
dc.relationChem.-Eur. J.
dc.rightsfechado
dc.rightshttp://olabout.wiley.com/WileyCDA/Section/id-406071.html
dc.sourceWeb of Science
dc.subjectab initio calculations
dc.subjectcollision-induced dissociation
dc.subjectin-molecule reactions
dc.subjectmass spectrometry
dc.subjectGas-phase
dc.subjectSoot Formation
dc.subjectIons
dc.subjectC3h3+
dc.subjectChemistry
dc.titleLocating the charge site in heteroaromatic cations
dc.typeArtículos de revistas


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