Resumo

WILSON, R. D.; AXWORTHY, A. E.  e  CHRISTE, K. O. Photochemistry Of Interhalogen Compounds. An. Asoc. Quím. Argent. [online]. 2005, vol.93, n.4-6, pp.1-20. ISSN 0365-0375.

The chemical kinetics of the UV-photochemical formations of ClF, ClF3 and ClF3O were studied. Unfiltered radiation from a 450-watt UV lamp and a dual-temperature reactor were used allowing periodic analysis of the reaction mixture by gas chromatography. Most of the effort was devoted to the formation of ClF3O from either ClF3 / O2 or the elements to obtain information relating to the optimum conditions and to the reaction mechanisms involved. The rate of ClF3O formation was the same for both reactant systems. The rate was found to increase with oxygen concentration and to be independent of the irradiation time. It was also shown to be proportional to the intensity of the 184.7 nm band of the Hg spectrum, indicating that the dissociation of O2 to two ground-state, 3P, oxygen atoms is the primary photochemical process. The following mechanism is proposed which requires the photochemical dissociation of ClF3 as well O2 + hν (184.7 nm) → O + O ClF3 + hν (200 to 350 nm) → ClF2 + F O + ClF2 → ClF2O ClF2O + F2 → ClF3O + F The photolysis of ClF3 was investigated under similar conditions. A photochemical steady state was quickly achieved where (F2) = (ClF) = α(ClF3). The value of α is about 1 at low pressures and about 3 at high pressures. A mechanism that accounts for these results is proposed. At a wavelength of 365 nm, the quantum yield of the reaction ClF + F2 + hν→ ClF3 was found to be about 1 and that of the reaction Cl2 + F2 + h ν → 2 ClF to be considerably less than 1. The latter result is quite interesting because Cl2 and F2 are expected to undergo a chain reaction. The magnitudes of the quantum yields determined for the formations of ClF3 and ClF have been verified in the independent investigations of H. J. Schumacher and coworkers.

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