Quantum-Chemical Kinetic Study of the Unimolecular Decomposition Reactions of 1-Bromo-3-Chloropropane

The pressure and temperature dependence of the thermal decomposition of 1-bromo-3-chloropropane has been theoretically investigated. The reaction takes place majorly through the elimination of HBr. Molecular properties of 1-bromo-3-chloropropane and transition states were derived from MN15/6-311++G(3df,3pd) and G4 quantum-chemical calculations. The resulting rate constants obtained from the unimolecular reaction rate theory for the high- and low-pressure limits of reaction BrCH₂CH₂CH₂Cl → CH₂CHCH₂Cl + HBr at 400-1000 K were k_∞ = 6.1 × 10¹³ exp(-57.2 kcal mol^-1/RT) s^-1 and k₀ = [BrCH₂CH₂CH₂Cl] 1.45 × 10^-1 (T/1000 K)^-7.9 exp(-55.9 kcal mol^-1/RT) cm³ molecule^-1 s^-1. A value of -26.3 ± 1.0 kcal mol^-1 for the standard enthalpy of formation of 1-bromo-3-chloropropane at 298 K was derived.