Matrix isolation FTIR and theoretical study of a-pyrone

Detalhes bibliográficos
Autor(a) principal: Breda, S.
Data de Publicação: 2004
Outros Autores: Reva, I., Lapinski, L., Fausto, R.
Tipo de documento: Artigo
Idioma: eng
Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
Texto Completo: http://hdl.handle.net/10316/17850
https://doi.org/10.1039/B309660B
Resumo: A combined matrix isolation FTIR and molecular orbital study on the photochemistry of alpha-pyrone (AP) was undertaken. The most efficient of the observed photoprocesses was the Norrish type I, ring opening reaction leading to conjugated ketene. Upon irradiation of matrix isolated AP with UV (λ>285 nm) light, rapid formation of Z isomers of the aldehyde–ketene was observed. After a few minutes of irradiation the IR bands assigned to these photoproducts stopped growing. Further irradiation generated, by excited state internal rotations around the central CC bond in the Z forms, new aldehyde–ketene isomers, which were assigned to the E forms of the conjugated ketene. These forms were identified in the present work for the first time. Upon subsequent UV (λ>337 nm) irradiation, the Z aldehyde–ketene isomers reverted back to the closed-ring, initial form of AP, while the E forms did not react further. The ring opening reaction occurring upon UV (λ>285 nm) irradiation was accompanied by very slow valence isomerization of AP to the Dewar form (2-oxa-3-oxobicyclo[2.2.0]hex-5-ene; OOBH). Observation of cyclobutadiene, produced by shorter wavelength UV irradiation (λ>235 nm) of OOBH, was also achieved in the present study. The structure of the cage confined complex of cyclobutadiene with CO2 was theoretically investigated. The possibility of formation of 4-formyl-2-cyclobutene-1-one, by photochemical ring closure of aldehyde–ketene isomers with the central CC bond and the ketene group in s–cis position with respect to each other is also discussed
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spelling Matrix isolation FTIR and theoretical study of a-pyroneA combined matrix isolation FTIR and molecular orbital study on the photochemistry of alpha-pyrone (AP) was undertaken. The most efficient of the observed photoprocesses was the Norrish type I, ring opening reaction leading to conjugated ketene. Upon irradiation of matrix isolated AP with UV (λ>285 nm) light, rapid formation of Z isomers of the aldehyde–ketene was observed. After a few minutes of irradiation the IR bands assigned to these photoproducts stopped growing. Further irradiation generated, by excited state internal rotations around the central CC bond in the Z forms, new aldehyde–ketene isomers, which were assigned to the E forms of the conjugated ketene. These forms were identified in the present work for the first time. Upon subsequent UV (λ>337 nm) irradiation, the Z aldehyde–ketene isomers reverted back to the closed-ring, initial form of AP, while the E forms did not react further. The ring opening reaction occurring upon UV (λ>285 nm) irradiation was accompanied by very slow valence isomerization of AP to the Dewar form (2-oxa-3-oxobicyclo[2.2.0]hex-5-ene; OOBH). Observation of cyclobutadiene, produced by shorter wavelength UV irradiation (λ>235 nm) of OOBH, was also achieved in the present study. The structure of the cage confined complex of cyclobutadiene with CO2 was theoretically investigated. The possibility of formation of 4-formyl-2-cyclobutene-1-one, by photochemical ring closure of aldehyde–ketene isomers with the central CC bond and the ketene group in s–cis position with respect to each other is also discussedRoyal Society of Chemistry2004info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articlehttp://hdl.handle.net/10316/17850http://hdl.handle.net/10316/17850https://doi.org/10.1039/B309660BengBreda, S.Reva, I.Lapinski, L.Fausto, R.info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2021-09-16T09:41:45Zoai:estudogeral.uc.pt:10316/17850Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T21:01:44.416027Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse
dc.title.none.fl_str_mv Matrix isolation FTIR and theoretical study of a-pyrone
title Matrix isolation FTIR and theoretical study of a-pyrone
spellingShingle Matrix isolation FTIR and theoretical study of a-pyrone
Breda, S.
title_short Matrix isolation FTIR and theoretical study of a-pyrone
title_full Matrix isolation FTIR and theoretical study of a-pyrone
title_fullStr Matrix isolation FTIR and theoretical study of a-pyrone
title_full_unstemmed Matrix isolation FTIR and theoretical study of a-pyrone
title_sort Matrix isolation FTIR and theoretical study of a-pyrone
author Breda, S.
author_facet Breda, S.
Reva, I.
Lapinski, L.
Fausto, R.
author_role author
author2 Reva, I.
Lapinski, L.
Fausto, R.
author2_role author
author
author
dc.contributor.author.fl_str_mv Breda, S.
Reva, I.
Lapinski, L.
Fausto, R.
description A combined matrix isolation FTIR and molecular orbital study on the photochemistry of alpha-pyrone (AP) was undertaken. The most efficient of the observed photoprocesses was the Norrish type I, ring opening reaction leading to conjugated ketene. Upon irradiation of matrix isolated AP with UV (λ>285 nm) light, rapid formation of Z isomers of the aldehyde–ketene was observed. After a few minutes of irradiation the IR bands assigned to these photoproducts stopped growing. Further irradiation generated, by excited state internal rotations around the central CC bond in the Z forms, new aldehyde–ketene isomers, which were assigned to the E forms of the conjugated ketene. These forms were identified in the present work for the first time. Upon subsequent UV (λ>337 nm) irradiation, the Z aldehyde–ketene isomers reverted back to the closed-ring, initial form of AP, while the E forms did not react further. The ring opening reaction occurring upon UV (λ>285 nm) irradiation was accompanied by very slow valence isomerization of AP to the Dewar form (2-oxa-3-oxobicyclo[2.2.0]hex-5-ene; OOBH). Observation of cyclobutadiene, produced by shorter wavelength UV irradiation (λ>235 nm) of OOBH, was also achieved in the present study. The structure of the cage confined complex of cyclobutadiene with CO2 was theoretically investigated. The possibility of formation of 4-formyl-2-cyclobutene-1-one, by photochemical ring closure of aldehyde–ketene isomers with the central CC bond and the ketene group in s–cis position with respect to each other is also discussed
publishDate 2004
dc.date.none.fl_str_mv 2004
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dc.identifier.uri.fl_str_mv http://hdl.handle.net/10316/17850
http://hdl.handle.net/10316/17850
https://doi.org/10.1039/B309660B
url http://hdl.handle.net/10316/17850
https://doi.org/10.1039/B309660B
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dc.publisher.none.fl_str_mv Royal Society of Chemistry
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dc.source.none.fl_str_mv reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
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