Bond energies bromine-carbon

The last example represents a fairly rare elimination of hydrogen fluoride in preference to hydrogen chloride, a reaction that deserves a more detailed discussion A comparison of bond dissociation energies of carbon-halogen bonds shows that the carbon-fluorine bond is much stronger than the carbon-chlorine, carbon-bromine, and carbon-iodme bonds 108-116, 83 5, 70, and 56 kcal/mol, respec-... 

The results of selective hydrolysis together with the percentages of isomers formed suggest that the facility for hydrolytic cleavage is in the order C-10 > C-8 > C-6. This order agrees with the order of bond energies between bromine and carbon atoms as calculated by the MINDO/3 method for the five isomeric monobromobenzo[6]tropoxazines. 

The substantial difference in the heats of reaction of ethane, ethene, and ethyne with bromine is reflected in a very important practical consideration in handling ethyne (acetylene), namely its thermodynamic stability relative to solid carbon and hydrogen gas. Unlike ethane, both ethene and ethyne can be shown from bond energies to be unstable with respect to formation of solid carbon and gaseous hydrogen ... 

Bromine and chlorine are two reactive halogens that have worked well for flame retardant purposes. Organo-fluorine compounds have not been as effective as flame retardant additives because the carbon-fluorine bond energy is so high that other events dominate at temperatures where halogenated flame retardants operate. ... 

Because this system is regenerative, halogenated flame retardants are very effective at relatively low load levels. Bromine is more effective than chlorine because the lower bond energy of the carbon to bromine bond. This allows the liberation of halide at the more favorable point in the combustion process. It is also believed that HCl is formed over a wider temperature range and is therefore present at lower concentrations in the flame front and is hence less effective than HBr. 

The structure of the iodinated transfer agent R-I, that is, the nature of the substituents in R R R C-I, is obviously important since it will determine its reactivity in radical polymerization. The weaker bond energy of the carbon-iodine bond (52kcalmor, 2.16 A, in CH3-I) compared to the carbon-bromine (65kcalmob, 1.97 A) and carbon-chlorine (78kcalmor, 1.79 A) is favorable for the formation of the active radical species. 

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