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Previous issue date: 2016-06-10 / Laser flash photolysis (LFP) studies have been performed in order to investigate the triplet reactivity toward hydrogen and electron donors of the benzo-fused furan psoralens 3-ethoxycarbonyl-2H-benzofuro[2,3-e]-1-benzopyran-2-one (1) and 3-ethoxycarbonyl-2H-benzofuro[3,2-d]-1-benzopyran-2-one (2). Photolysis of the psoralens 1 and 2 results in the formation of the corresponding triplet excited state which is efficiently quenched by DABCO, triethylamine and phenols containing polar substituents. The reaction of the triplet state of 1 and 2 with electron donors (DABCO and triethylamine) leads to the formation of the corresponding anion radical whereas with phenols the corresponding aryloxyl radical was easily detected. Quenching rate constants for psoralen 2 are at least one order of magnitude greater than for 1. The Hammett plot for the reaction of 1 and 2 with phenols yielded a reaction constant ? of - 1.88?0.29 and -1.60?0.21, respectively, which reflects the high electrophilicity of the carbonyl group of both psoralens. / Estudos empregando a t?cnica de Fot?lise por Pulso de Laser foram realizados a fim de investigar a reatividade dos estados excitados triplete dos benzopsoralenos 3-etoxicarbonil-2-H-benzofuro[2,3-e]-1-benzopiran-2-ona (Pso 1) e 3-etoxicarbonil-2-H-benzofuro[3,2-d]-1-benzopiran-2-ona (Pso 2) frente a doadores de el?tron e hidrog?nio. A fot?lise dos psoralenos Pso 1 e Pso 2 resulta na forma??o do estado excitado triplete correspondente os quais reagem de forma eficiente com DABCO, trietilamina, fenol e seus derivados contendo substituintes polares. A rea??o dos estados excitados triplete de Pso 1 e Pso 2 com doadores de el?tron (DABCO e trietilamina) levou ? forma??o do ?nion radical correspondente, enquanto que na presen?a de doadores de hidrog?nio como o fenol e seus derivados houve forma??o dos radicais fenoxila correspondentes. As constantes de velocidade obtidos para Pso 2 s?o pelo menos uma ordem de grandeza maior do que as obtidas para Pso 1. Um gr?fico de Hammett para as rea??es do triplete de Pso 1 e Pso 2 frente a fen?is e seus derivados produziu constante de rea??o (?? de - 1,88?0,29 e de -1,60 ? 0,21, respectivamente, o que reflete a alta eletrofilicidade do grupo carbon?lico para ambos os benzopsoralenos.
| Identifer | oai:union.ndltd.org:IBICT/oai:localhost:jspui/1622 |
| Date | 10 June 2016 |
| Creators | MAIA, Julio Eduardo Paiva Sena |
| Contributors | Ferreira, Jos? Carlos Netto, Sobrinho, Dari Cesarim, Ferreira, Jos? Carlos Neto, Lima, Aurea Echevarria Aznar Neves, SIlva, Francisco de Assis da, Garden, Nanci C?mara de Lucas, Correa, Rodrigo Jos? |
| Publisher | Universidade Federal Rural do Rio de Janeiro, Programa de P?s-Gradua??o em Qu?mica, UFRRJ, Brasil, Instituto de Ci?ncias Exatas |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Biblioteca Digital de Teses e Dissertações da UFRRJ, instname:Universidade Federal Rural do Rio de Janeiro, instacron:UFRRJ |
| Rights | info:eu-repo/semantics/openAccess |
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