Kinetics of Elementary Reactions in the Chain Chlorination of Cyclopropane

The kinetics of elementary reactions involved in the chain chlorination of cyclopropane are examined using a combination of absolute and relative rate constant measurements and first principles electronic structure calculations. Relative rate methods are used in a smog chamber FTIR apparatus to determine k (Cl + c -C 3 H 6 ) = (1.15 ± 0.17) × 10 -13 and k (Cl + c -C 3 H 5 Cl) = (1.06 ± 0.18) × 10 -12 cm 3 molecule -1 s -1 in 10−700 Torr of air, or N 2, diluent at 296 K. Absolute rate coefficients for the reaction of Cl with cyclopropane are measured between 293 and 623 K by a laser-photolysis/CW infrared absorption method. The data can be represented in Arrhenius form as k (Cl + c -C 3 H 6 ) = ((1.8 ± 0.3) × 10 -10 cm 3 molecule -1 s -1 )e -(2150±100)/ T . To support the experimental investigations, first principles electronic structure calculations are performed. Vibrational spectra of c -C 3 H 5 Cl, c -C 3 H 4 Cl 2, and c -C 3 H 3 Cl 3 are calculated and are presented. gem -C 3 H 4 Cl 2 is calculated to be the kinetically and thermodynamically most favored dichlorocyclopropane. The experimental observations are consistent with the computational findings.