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Title: | Bond dissociation energies from equilibrium studies: Part 5.—The equilibria Br2+ CH2F2⇌ HBr + CHF2Br and Br2+ CH3F ⇌ HBr + CH2FBr. Determination of D(CHF2—Br) and ΔH °f(CHF2Br, g) |
Authors: | Okafo, Ernest N. Whittle, Eric |
Keywords: | Chemistry Bond Dissociation Equilibrium Journal of the Chemical Society : Faraday Transaction - I |
Issue Date: | 1974 |
Publisher: | Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (07) |
Abstract: | The equilibrium, Br2+ CH2F2⇌ HBr + CHF2Br (4), has been studied in the temperature range 371–479°C, with equilibrium being approached from both sides. Third-law calculations lead to ΔH°4=–39.9 ± 0.3 kJ mol–1 at 298 K from which, ΔH°f(CHF2Br, g)=–425.3 ± 0.9 kJ mol–1, D(CHF2—Br)= 289 ± 8 kJ mol–1, at 298 K. The value of ΔH°f(CHF2Br) is combined with published kinetic data on the pyrolysis of CHF2Br to give, ΔH°f(CF2)=–194 ± 9 kJ mol–1 at 298 K. The system, Br2+ CH3F ⇌ HBr + CH2FBr, was also studied but true equilibrium was not achieved owing to unexpected formation of CH3Br as a major product. Possible mechanisms involving breaking of a C—F bond and conversion of CHF2Br or CH3F to CH3Br are discussed. |
URI: | http://dspace.bits-pilani.ac.in:8080/jspui/handle/123456789/19013 |
Appears in Collections: | Journal Articles (before-1995) |
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