File Download

There are no files associated with this item.

  Links for fulltext
     (May Require Subscription)
Supplementary

Article: Characterization of reactive intermediates generated during photolysis of 4-acetoxy-4-aryl-2,5-cyclohexadienones: Oxenium ions and aryloxy radicals

TitleCharacterization of reactive intermediates generated during photolysis of 4-acetoxy-4-aryl-2,5-cyclohexadienones: Oxenium ions and aryloxy radicals
Authors
Issue Date2008
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.html
Citation
Journal Of The American Chemical Society, 2008, v. 130 n. 47, p. 16021-16030 How to Cite?
AbstractAryloxenium ions 1 are reactive intermediates that are isoelectronic with the better known arylcarbenium and arylnitrenium ions. They are proposed to be involved in synthetically and industrially useful oxidation reactions of phenols. However, mechanistic studies of these intermediates are limited. Until recently, the lifetimes of these intermediates in solution and their reactivity patterns were unknown. Previously, the quinol esters 2 have been used to generate 1, which were indirectly detected by azide ion trapping to generate azide adducts 4 at the expense of quinols 3, during hydrolysis reactions in the dark. Laser flash photolysis (LFP) of 2b in the presence of O2 in aqueous solution leads to two reactive intermediates with γmax 360 and 460 nm, respectively, while in pure CH3CN only one species with λmax 350 nm is produced. The intermediate with Amax 460 nm was previously identified as lb based on direct observation of its decomposition kinetics in the presence of N3 -, comparison to azide ion trapping results from the hydrolysis reactions, and photolysis reaction products (3b). The agreement between the calculated (B3LYP/6-31G(d)) and observed time-resolved resonance Raman (TR3) spectra of 1b further confirms its identity. The second intermediate with λ max 360 nm (350 nm in CH3CN) has been characterized as the radical 5b, based on its photolytic generation in the less polar CH 3CN and on isolated photolysis reaction products (6b and 7b). Only the radical intermediate 5b is generated by photolysis in CH3CN, so its UV-vis spectrum, reaction products, and decay kinetics can be investigated in this solvent without interference from 1b. In addition, the radical 5a was generated by LFP of 2a and was identified by comparison to a published UV-vis spectrum of authentic 5a obtained under similar conditions. The similarity of the UV-vis spectra of 5a and 5b, their reaction products, and the kinetics of their decay confirm the assigned structures. The lifetime of 1b in aqueous solution at room temperature is 170 ns. This intermediate decays with first-order kinetics. The radical intermediate 5b decomposes in a biphasic manner, with lifetimes of 12 and 75 μs. The decay processes of 5a and 5b were successfully modeled with a kinetic scheme that included reversible formation of a dimer. The scheme is similar to the kinetic models applied to describe the decay of other aryloxy radicals. © 2008 American Chemical Society.
Persistent Identifierhttp://hdl.handle.net/10722/58403
ISSN
2015 Impact Factor: 13.038
2015 SCImago Journal Rankings: 7.123
ISI Accession Number ID
Funding AgencyGrant Number
American Chemical Society Petroleum Research Fund43176-AC4
Department of Chemistry and Biochemistry at Miami University for a Dissertation Fellowship
Miami University
NSF
OSU Graduate School for a Presidential Fellowship
Research Grants Council (RGC) of Hong KongHKU 7040/06P
Croucher Foundation (2006-07)
University of Hong Kong for an Outstanding Researcher Award (2006)
Funding Information:

We thank the Donors of the American Chemical Society Petroleum Research Fund (Grant No. 43176-AC4) for support of this work. Y.-T.W. thanks the Department of Chemistry and Biochemistry at Miami University for a Dissertation Fellowship, and K.J.J. thanks Miami University for an Undergraduate Summer Scholars award. The support of the NSF in Columbus and OSU Center for Chemical and Biophysical Dynamics is greatly appreciated. J.W. thanks the OSU Graduate School for a Presidential Fellowship. This work was supported in part by a grant from the Research Grants Council (RGC) of Hong Kong (HKU 7040/06P) to D.L.P. D.L.P. thanks the Croucher Foundation for the award of a Croucher Foundation Senior Research Fellowship (2006-07) and the University of Hong Kong for an Outstanding Researcher Award (2006).

References
Grants

 

DC FieldValueLanguage
dc.contributor.authorWang, YTen_HK
dc.contributor.authorJin, KJen_HK
dc.contributor.authorLeopold, SHen_HK
dc.contributor.authorWang, Jen_HK
dc.contributor.authorPeng, HLen_HK
dc.contributor.authorPlatz, MSen_HK
dc.contributor.authorXue, Jen_HK
dc.contributor.authorPhillips, DLen_HK
dc.contributor.authorGlover, SAen_HK
dc.contributor.authorNovak, Men_HK
dc.date.accessioned2010-05-31T03:29:41Z-
dc.date.available2010-05-31T03:29:41Z-
dc.date.issued2008en_HK
dc.identifier.citationJournal Of The American Chemical Society, 2008, v. 130 n. 47, p. 16021-16030en_HK
dc.identifier.issn0002-7863en_HK
dc.identifier.urihttp://hdl.handle.net/10722/58403-
dc.description.abstractAryloxenium ions 1 are reactive intermediates that are isoelectronic with the better known arylcarbenium and arylnitrenium ions. They are proposed to be involved in synthetically and industrially useful oxidation reactions of phenols. However, mechanistic studies of these intermediates are limited. Until recently, the lifetimes of these intermediates in solution and their reactivity patterns were unknown. Previously, the quinol esters 2 have been used to generate 1, which were indirectly detected by azide ion trapping to generate azide adducts 4 at the expense of quinols 3, during hydrolysis reactions in the dark. Laser flash photolysis (LFP) of 2b in the presence of O2 in aqueous solution leads to two reactive intermediates with γmax 360 and 460 nm, respectively, while in pure CH3CN only one species with λmax 350 nm is produced. The intermediate with Amax 460 nm was previously identified as lb based on direct observation of its decomposition kinetics in the presence of N3 -, comparison to azide ion trapping results from the hydrolysis reactions, and photolysis reaction products (3b). The agreement between the calculated (B3LYP/6-31G(d)) and observed time-resolved resonance Raman (TR3) spectra of 1b further confirms its identity. The second intermediate with λ max 360 nm (350 nm in CH3CN) has been characterized as the radical 5b, based on its photolytic generation in the less polar CH 3CN and on isolated photolysis reaction products (6b and 7b). Only the radical intermediate 5b is generated by photolysis in CH3CN, so its UV-vis spectrum, reaction products, and decay kinetics can be investigated in this solvent without interference from 1b. In addition, the radical 5a was generated by LFP of 2a and was identified by comparison to a published UV-vis spectrum of authentic 5a obtained under similar conditions. The similarity of the UV-vis spectra of 5a and 5b, their reaction products, and the kinetics of their decay confirm the assigned structures. The lifetime of 1b in aqueous solution at room temperature is 170 ns. This intermediate decays with first-order kinetics. The radical intermediate 5b decomposes in a biphasic manner, with lifetimes of 12 and 75 μs. The decay processes of 5a and 5b were successfully modeled with a kinetic scheme that included reversible formation of a dimer. The scheme is similar to the kinetic models applied to describe the decay of other aryloxy radicals. © 2008 American Chemical Society.en_HK
dc.languageengen_HK
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journals/jacsat/index.htmlen_HK
dc.relation.ispartofJournal of the American Chemical Societyen_HK
dc.titleCharacterization of reactive intermediates generated during photolysis of 4-acetoxy-4-aryl-2,5-cyclohexadienones: Oxenium ions and aryloxy radicalsen_HK
dc.typeArticleen_HK
dc.identifier.emailPhillips, DL:phillips@hku.hken_HK
dc.identifier.authorityPhillips, DL=rp00770en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1021/ja805336den_HK
dc.identifier.scopuseid_2-s2.0-56749175085en_HK
dc.identifier.hkuros157179en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-56749175085&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume130en_HK
dc.identifier.issue47en_HK
dc.identifier.spage16021en_HK
dc.identifier.epage16030en_HK
dc.identifier.isiWOS:000263319600060-
dc.publisher.placeUnited Statesen_HK
dc.relation.projectTime-resolved resonance raman spectroscopic investigation of selected reactions of arylnitrenium ions with guanine derivatives-
dc.identifier.scopusauthoridWang, YT=23029292900en_HK
dc.identifier.scopusauthoridJin, KJ=25654952100en_HK
dc.identifier.scopusauthoridLeopold, SH=23100306600en_HK
dc.identifier.scopusauthoridWang, J=7701314990en_HK
dc.identifier.scopusauthoridPeng, HL=14052735300en_HK
dc.identifier.scopusauthoridPlatz, MS=7004584689en_HK
dc.identifier.scopusauthoridXue, J=23007272500en_HK
dc.identifier.scopusauthoridPhillips, DL=7404519365en_HK
dc.identifier.scopusauthoridGlover, SA=34771053700en_HK
dc.identifier.scopusauthoridNovak, M=7402369268en_HK

Export via OAI-PMH Interface in XML Formats


OR


Export to Other Non-XML Formats