Autor(es):
Kus, Nihal 
; Breda, Susana ; Reva, Igor ; Tasal, Erol ; Ogretir, Cemil ; Fausto, Rui
Data: 2007
Identificador Persistente: http://hdl.handle.net/10316/17933
Origem: Estudo Geral - Universidade de Coimbra
Descrição
The infrared spectrum of monomeric unsubstituted coumarin (C<sub>9</sub>H<sub>6</sub>O<sub>2</sub>; 2 H-1-benzopyran-2-one), isolated in solid argon at 10 K is presented and assigned. The UV-induced ( λ > 200 nm) unimolecular photochemistry of the matrix-isolated compound was studied experimentally. Three main photoreactions were observed: (a) decarboxylation of the compound and formation of benzocyclobutadiene and CO<sub>2</sub>, with the Dewar form of coumarin as intermediate; (b) isomerization of the compound, leading to production of a conjugated ketene; and (c) decarbonylation, leading to formation of CO and benzofuran complex. Further decomposition of benzofuran to produce ethynol is suggested. Photochannels (a) and (b) correspond to those previously observed for matrix-isolated α-pyrone and its sulfur analogs ( Phys. Chem. Chem. Phys. 2004, 6, 929; J. Phys. Chem. A 2006, 110, 6415), while route (c) is similar to the UV-induced photochemistry of coumarin in the gaseous phase ( J. Phys. Chem. A 2000, 104, 1095). Interpretation of the experimental data is supported by extensive calculations performed at the B3LYP/6-311++G(d,p), MP2/6-31G(d,p) and MP2/6-311++G(d,p) levels. [ABSTRACT FROM AUTHOR].
