title: Photochemistry and vibrational spectra of matrix-isolated methyl 4-chloro-5-phenylisoxazole-3-carboxylate.
abstract: Methyl 4-chloro-5-phenylisoxazole-3-carboxylate (MCPIC) has been synthesized, isolated in low temperature argon and xenon matrices, and studied by FTIR spectroscopy. The characterization of the low energy conformers of MCPIC was made by undertaking a systematic investigation of the DFT(B3LYP)/6-311++G(d,p) potential energy surface of the molecule. The theoretical calculations predicted the existence of three low energy conformers. Two of them (I and II) were observed experimentally in the cryogenic matrices. The third one (III) was found to be converted into conformer II during deposition of the matrices, a result that is in agreement with the predicted low III → II energy barrier (<0.3 kJ mol(-1)). In situ UV irradiation (λ > 235 nm) of matrix-isolated MCPIC yielded as final photoproduct the corresponding oxazole (methyl 4-chloro-5-phenyl-1,3-oxazole-2-carboxylate). Identification of the azirine and nitrile-ylide intermediates in the spectra of the irradiated matrices confirmed their mechanistic relevance in the isoxazole → oxazole photoisomerization.
authors.affiliation: Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal.
authors.forename: Susy
authors.initials: S
authors.lastname: Lopes
authors.forename: Cláudio M
authors.initials: CM
authors.lastname: Nunes
authors.forename: Andrea
authors.initials: A
authors.lastname: Gómez-Zavaglia
authors.forename: Teresa M V D
authors.initials: TM
authors.lastname: Pinho e Melo
authors.forename: Rui
authors.initials: R
authors.lastname: Fausto
mesh_terms: D001128:Argon / Q000737:chemistry; D003198:Computer Simulation; D004735:Energy Transfer; D007555:Isoxazoles / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010080:Oxazoles / Q000737:chemistry*; D010777:Photochemistry; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared / Q000379:methods; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013696:Temperature; D013816:Thermodynamics; D014466:Ultraviolet Rays; D014732:Vibration; D014978:Xenon / Q000737:chemistry
chemical_list: D007555:Isoxazoles; D010080:Oxazoles; C558467:methyl 4-chloro-5-phenylisoxazole-3-carboxylate; D014978:Xenon; D001128:Argon