Density functional theory calculation on the C—H bond insertion reaction of dibromocarbene with acetaldehyde.

The insertion reaction mechanism of CBr₂with CH₃CHO has been studied by using the B3LYP/6-31G(d) method. The geometries of reactions, transition state and products were completely optimized. All the energy of the species was obtained at the CCSD(T)/6-31 G(d) level. All the transition state is verified by the vibrational analysis and the internal reaction coordinate (IRC) calculations. The results show that the propionaldehyde (^HP1) is the main product of CH₂ insertion with CH₃CHO. The calculated results indicated that all the major pathways of the reaction were obtained on the singlet potential energy surface. The singlet CBr₂ not only can insert the C_α-H [reaction 1(1)]) but also can react with C_βH [reaction II(1)]. The statistical thermodynamics and Eyring transition state theory with Wigner correction are used to study the thermodynamic and kinetic characters of 1(1) and 11(1) in temperature range from 100 to 2200 K. The results show that the appropriate reaction temperature rang is 250 to 1750 K and 250 to 1600 K at 1.0 atm for 1(1) and 11(1) respectively. The rate constant and equilibrium constant are distinct in the range from 250 to 1000 K so that 1(1) more easily occurs, while the reactions are not selected in the temperature range of 1000-1600 K. [ABSTRACT FROM AUTHOR]