Chemiluminescence and Radical Reactions in Diffusion Flames of Alkali Metals with Organic Halides

Chemiluminescent reactions in diffusion flames of alkali metals with haloforms and carbon tetrahalides appear to provide examples of reactions in which essentially all of the exothermicity appears as vibration in a newly formed bond. A self-consistent account of the intensity distributions in the flame spectra requires that, in CX4—K flames, both excited and unexcited carbon atoms participate in the reactions, C+CX→C2*+X, and that the X atoms be produced both in the ground and first excited states. Excited C atoms appear not to be produced in CHX3—K flames in appreciable concentrations. The excited C2 intensity distributions in emission are compatible with the bond dissociation energies, C–Cl=77 kcal, C–Br=66 kcal, and C–I=50 kcal, with uncertainties of about 4 kcal in each.