The following net processes occur in a system containing chlorine and hydrogen bromide :
(1)
These reactions have been followed spectrophotometrically in a gas phase stopped flow apparatus. The first two reactions are strongly surface catalyzed on untreated glass or quartz, but are much slower if the cell surface has been covered with silicone and photochlorinated. Rates in such systems are first order in each reactant, and comparable limiting rate constants have been obtained in cells with different methods of preparing the surfaces and with different surface-to-volume ratios. These experimental rate constants must be equal to or greater than those of the homogeneous bimolecular reactions. Then limiting rate constants at 35Β°C in liters per mole per second are kl 5 0.8, kz 2 15, and k3 5 0.04. Reactions of HI with (212, Br2, and IC1 are all much faster than reaction (2).
These observations and those of other diatomic molecule reactions can be rationalized if halogen and hydrogen halide molecules react through a transition state in which the hydrogen atom is near the center of a triangle of three halogen atoms.
* More detailed description of apparatus, calculations, and results will be found in Wen [5].
We were unbale to generate tightly adhering teflon coatings.