Articles written in Journal of Chemical Sciences

    • Kinetics of the thermal decomposition of tetramethylsilane behind the reflected shock waves between 1058 and 1194 K


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      Thermal decomposition of tetramethylsilane (TMS) diluted in argon was studied behind thereflected shock waves in a single pulse shock tube (SPST) in the temperature range of 1058–1194 K. The majorproducts formed in the decomposition are methane $ (CH_{4}$) and ethylene $(C_{2}H_{4})$; whereas ethane and propylenewere detected in lower concentrations. The decomposition of TMS seems to be initiated via Si-C bondscission by forming methyl radicals $ (CH_{3})$ and trimethylsilyl radicals $((CH_{3})_{3}Si)$. The total rate coefficientsobtained for the decomposition of TMS were fit to Arrhenius equation in two different temperature regions1058–1130K and 1130–1194 K. The temperature dependent rate coefficients obtained are $ k_{total}$ (1058–1130 K)

      =$ (4.61 ± 0.70) \times10^{18}$ exp (−(79.9 kcal mol−1 ± 3.5)/RT) s−1,$ k_{total}$ (1130-1194 K) =$ (1.33 ± 0.19) \times 10^{6}$ exp(−(15.3 kcal mol−1 ± 3.5)/RT) s−1. The rate coefficient for the formation of $CH_{4}$ is obtained to be $ k_{methane}$(1058–1194 K) =$ (4.36 ± 1.23) \ times10^{14}$ exp (−(61.9 kcal mol−1±4.9)/RT) s−1. A kinetic scheme containing 21species and 38 elementary reactions was proposed and simulations were carried out to explain the formation ofall the products in the decomposition of tetramethylsilane.

    • Rate coefficients for hydrogen abstraction reaction of pinonaldehyde C10H16O2 with Cl atoms between 200 and 400 K: A DFT study


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      The kinetics of the reaction between pinonaldehyde C10H16O2 and Cl atom were studied usinghigh level ab initio G3(MP2) and DFT based MPWB1K/6-31+G(d) and MPW1K/6-31+G(d) levels of theoriescoupled with Conventional Transition State Theory in the temperature range between 200 and 400 K. Thenegative temperature dependent rate expression for the title reaction obtained with Wigner’s and Eckart’s symmetricaltunneling corrections are k(T)=(5.1 ± 0.56) × 10−19T2.35exp[(2098 ± 2)/T] cm3 molecule-1 s-1, and k(T)=(0.92 ± 0.18) × 10-19T2.60exp[(2204 ± 4)/T] cm3 molecule-1 s-1, respectively, at G3(MP2)//MPWB1Kmethod. The H abstraction reaction from the –CHO group was found to be the most dominant reaction channelamong all the possible reaction pathways and its corresponding rate coefficient at 300 K is kEckart’s unsymmetrical= 3.86 ×10-10 cm3 molecule-1 s-1. Whereas the channel with immediate lower activation energy is the H-abstraction from –CH- group (Tertiary H-abstraction site, Cg). The rate coefficient for this channel is kCg(Eckart’s unsymmetrical) = 1.83 ×10-15 cm3 molecule-1 s-1 which is smaller than the dominant channel byfive orders of magnitude. The atmospherically relevant parameters such as lifetimes were computed in thisinvestigation of its reaction with Cl atom.

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