Reaction mechanisms and kinetics of the elimination processes of 2-chloroethylsilane and derivatives: A DFT study using CTST, RRKM, and BET theories

Abstract

The thermal decomposition kinetics of 2-chloroethylsilane and derivatives in the gas phase has been studied computationally using density functional theory, along with various exchange-correlation functionals (UM06-2x and ωB97XD) and the aug-cc-pVTZ basis set. The calculated energy profile has been supplemented with calculations of kinetic rate constants under atmospheric pressure and in the fall-off regime, using transition state theory (TST) and statistical Rice−Ramsperger−Kassel−Marcus (RRKM) theory. Activation energies and rate constants obtained using the UM06-2x/aug-cc-pVTZ approach are in good agreement with the experimental data. The decomposition of 2-chloroethyltriethylsilane species into the related products [C 2 H 4 +Et 3 SiCl] is characterized by 6 successive structural stability domains associated to the sequence of catastrophes C 8 H 19 SiCl: 6-C † FCC † [FF]-0: C 6 H 15 SiCl + C 2 H 4. Breaking of Si−C bonds and formation of Si−Cl bonds occur in the vicinity of the transition state.

Computational studies on thermo-kinetics aspects of pyrolysis of isopropyl acetate and its methyl, bromide and hydroxyl derivatives

“…By integrating the probability of transmission, p ( E ), which is identical to the over Boltzmann distribution of energies, the Eckart tunneling factor, κ ( T ), is used to correct the calculated TST rate constants ( Eq. (2) ) [ 60 ]: where Δ H f ≠,0K denotes the zero-point corrected energy barriers in the forward direction computed by the KiSThelP package [ 61 ], to calculate rate coefficients at various temperatures [ 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 ]. In all calculations, a scaling factor of 0.99 was applied to the calculated frequencies using the CBS-QB3 method [ 71 ].…”

Kinetics Studies on the Tautomeric Reaction of 4-Amino-5-Methyl-2,4-Dihydro-3h-1,2,4-Triazole-3-Thione in the Gas Phase: DFT and CBS-Qb3 Methods Using Transition State Theory

“…Reaction symmetry number σ =1 is taken into consideration for the studied reactions according to the point groups of symmetries of the all stationary points. Kinetic rate constants are corrected by multiplying the TST rate constants in the Wigner [58,59] and Eckart [60,61] tunneling correction factors. The Wigner tunneling correction is given by (2) where Im(u i ) is the imaginary vibrational frequency of the relevant transition state.…”