kuş, nihal anadolu university - faculty of science - department of physics, Eskişehir, Turkey , kuş, nihal university of coimbra - faculty of sciences and technology - department of chemistry, Coimbra, Portugal

STRUCTURAL CHARACTERIZATION AND PHOTOCHEMISTRY OF 2-CHLORO-6-FLUOROBENZOIC ACID ISOLATED IN A XENON MATRIX

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2-Chloro-6-fluorobenzoic acid (ClFBA) was studied by low temperature solid state FTIR spectroscopy in a Xe matrix and complemented by DFT(B3LYP)/6-311++G(d,p) calculations. According to the theoretical calculations, the ClFBA molecule exists in three different conformers. Conformers II and III are ca.17 kJ mol-1 higher in energy than the most stable conformer (I), and possess a trans carboxylic acid moiety, while form I has this group in the cis conformation. According to the energy data predicted theoretically only the conformer I was expected to be present in the cryogenic xenon matrix, a result that was confirmed experimentally. Attempts for in situ generation and detection of forms II and III by near-IR (2VOH; 6867 cm^-1) excitation of conformer I indicated that in solid xenon, once produced, these conformers promptly relax by tunneling to the most stable conformer. Laser UV (λ = 235 nm) excitation of matrix-isolated ClFBA led to prompt decarboxylation of the compound, with production of CO2 and 1-chloro-3-fluorobenzene (ClFB), whose vibrational signatures could be doubtlessly identified in the spectra of the photolysed matrix.

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2 , Chloro , 6 , fluorobenzoic acid , Matrix isolation spectra , DFT(B3LYP) calculations , FTIR spectroscopy , 1 , Chloro , 3 , fluorobenzene

Anadolu University Journal of Science and Technology. A : Applied Sciences and Engineering

322