The Exchange Reaction between Bromine and Bromotrichloromethane
1949; American Institute of Physics; Volume: 17; Issue: 2 Linguagem: Inglês
10.1063/1.1747207
ISSN1520-9032
Autores Tópico(s)Water Treatment and Disinfection
ResumoThermal exchange of the bromine in CCl3Br with Br2 has been measured in the temperature range from 100° to 135°C in liquid CCl3Br, in the range from 135° to 170°C in CCl4 solution, and in the range from 150° to 220°C in the gas phase. The activation energy has been found to be approximately 29 kcal. mole−1 in each phase. The rate of exchange has been found to be proportional to the first power of the CCl3Br concentration and to the square root of the bromine concentration, indicating an atomic mechanism. The values of the rate constants obtained in the liquid and gas phases are approximately equal. From the results it may be deduced that the activation energy for the step which initiates the exchange, i.e., either CCl3Br+Br→CCl3+Br2 or the reaction CCl3Br+Br*→CCl3Br*+Br is about7 kcal. mole−1. This value is in the range of values of 5–10 kcal. mole−1 indicated by previous experiments on the analogous photochemical reaction in carbon tetrachloride solution. The thermal reaction has been found to be much less sensitive to oxygen than various previously studied photo-chemical halogenation reactions. Analysis of the results suggests that the ``cage'' effect may appreciably lower the quantum yield of the photo-chemical reaction in the liquid phase.
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