Electron diffraction study of the thermal decomposition of BrCCl3

The thermal decomposition of bromotrichloromethane was studied in the gas phase by electron diffraction. An oven was incorporated into the sample inlet system of a conventional photographic plate unit to decompose the sample. Three different diffraction patterns were recorded and analyzed. A peak in the radial distribution curve corresponding to a normal carbon‐bromine bond was absent. However, in order to satisfy stoichiometry requirements and to match the areas of all of the peaks, it was necessary to introduce species with an abnormally long carbon‐bromine bond length. For each of the three diffraction patterns, the major components in the scattering volume were found to be mixtures of BrCCl₃/BrCCl₂/CCl₄/CCl₃, C₂Cl₄/C₂Cl₆, and BrCl/Br₂. Except for the $\mathrm{C–Br}$ bond, all distances and angles had normal values. A plausible explanation of the lengthening $\text{(∼ 0.15\hspace{0.17em}}\mathrm{\AA })$ of the $\mathrm{C–Br}$ bond is that a long‐lived excited state of BrCCl₃/BrCCl₂ was formed as an intermediate in the reaction.