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Changes of generalized normal-mode vibrational frequencies as a function of s (amu)1/2 Bohr at the CCSD(T)//MP2/6-311G(d,p) level for reactions R1b and R2b. a For reaction R1b, b for reaction R2b
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Multichannel gas-phase reactions of CH3OCH2CH2Cl/CH3CH2OCH2CH2Cl with chlorine atom and hydroxyl radical have been investigated using ab initio method and canonical variational transition-state dynamic computations with the small-curvature tunneling correction. Further energetic information is refined by the coupled-cluster calculations with single...
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... For the reactions initiated by Cl atoms with methylbenzene and 2-methylfuran, we have estimated atmospheric lifetimes from 49 to 68 days for reactions based on a global Cl atom concentration of 1.10 4 atoms cm −3 [118]. However, in some marine regions, peak values of 1.10 5 atoms cm −3 have been observed [119]. Under such circumstances, the reaction of Cl with these VOCs can be a significant, if not dominant, loss process. ...
Pyrolysis has been applied to soybean residues from 400 °C to 600 °C to obtain value-added molecules. Thebiowaste has been previously physicochemically characterized and the temperature effect on products distribu-tion has been evaluated. The results show that the liquid product (bio-oil) reached a maximum yield at 600 °C,while the solid product (bio-char) has a maximum performance at 400 °C. Among the desired products in bio-oil,aromatic hydrocarbons have been improved with the increment of temperature, with a maximum at 550 °C. Fornon-condensable products, CO2 was the highest emitted compound at all temperatures, together with CO as aconsequence of cellulose and hemicellulose thermal decomposition. The minimal CH4 release is caused by thelow biomass lignin content. In contrast to previous studies, the majority of the volatile organic compounds(VOCs) released during soybean residue thermal pyrolysis were identified for the first time. Aromatic hydrocar-bons were predominant for every temperature, with methylbenzene as the major contributor. The largest relativeproportion of aromatics was attained at 450 °C. 2-methylbutanal, 3-methylbutanal and 2-methylfuran werefound in this phase as meaningful compounds. As for bio-char, it has shown a higher heating value of 5756 kcal/kg. In this way, it could be considered as a good alternative for power generation. Therefore, the great potentialof soybean residue pyrolysis products requires an exhaustive analysis .
... The nature of CCSD(T) wave function was verified by performing T1 diagnostic test and the obtained values were less than the threshold value of 0.045 for the open-shell systems [26][27][28]. This clearly indicated that the wave functions have no multi-reference character. ...
... The spin contamination of the studied species were examined before and after annihilation and the obtained 〈S 2 〉 values were found to be 0.751 (for all the species) before annihilation. This was in good agreement with the expected value of 0.75 after annihilation for the pure doublet states [28] and hence, the spin contamination was negligible. ...
The reaction kinetics of dimethoxymethane (DMM) towards H atom abstraction by hydroperoxy and methyl peroxy radicals were investigated using the G4 composite method. All the studied reactions were found to be endothermic and non-spontaneous in nature. Canonical Variational Transition State Theory in combination with Small Curvature Tunneling corrections were adopted to calculate the rate coefficients in the temperature range of 400 – 1500K. The Arrhenius expressions for the reaction of DMM with CH3OO• and HO•2 radicals were obtained as ktotal = 1.50 × 10⁻¹² exp (-8159/T) and ktotal = 4.40 × 10⁻¹² exp (-7251/T) cm³molecule⁻¹s⁻¹ respectively.
... Whereas in Fig. 4b and c we can easily observed that TST and CVT/SCT with CVT rate constants are separated from each other at the whole temperature, indicating that both the variational and tunneling effects play a significant part in the calculation of the rate constants. Similar conclusions were also reflected in the NO 3 -initiated reactions of CH 3 OCH 3 and NO 3 radical with CH 3 I and C 2 H 5 I species [13,27]. In order to further understand the variation of the title reaction overall rate constants within the temperature range of 200e400 K, it is shown in Fig. 5. ...
... Researchers have shown that CFCs derivatives pose environmental hazards to ozone by diffusing into stratosphere and deplete it at a rate faster than it can be replaced in the atmosphere (Baidya et al., 2017;Garfield, 1988;Molina and Rowland, 1974;Orkin et al., 1999;Papadimitriou et al., 2007;Rowland, 1996;Rohrer and Berresheim, 2006;Rowley and Ferracci, 2014;WMO, 2010). For this fact, international restrictions and warning were placed on usage of CFCs as agreed upon in the Montreal Protocol (Good et al., 1998;Ye at al., 2016). Instead, alternative compounds with less or no posing ability to ozone is recommended as substantial substitutes for the CFCs (Espinosa-Garcia, 2003;Galano et al., 2010;MWO, 2010). ...
An Insilco study was carried out on the thermochemistry, mechanism and kinetics of the Hydrogen abstraction reaction of 1,1-difluoro-2-methoxypropane (CH3CH(OCH3)CHF2) with the Bromine monoxide radical (BrO) using the Density Functional Theory (DFT) based M06-2X/6-311++G** method. The energy values were immediately improved via optimization at DFT/M06-2X/6-311++G(2df,2p) level (single-point calculations) of the reacting species involved. The Monte Carlo search on the investigating hydrofluoroether (HFE) showed nine conformers with the lowest global minimum conformer being predicted and considered for this work. The results of this study showed that the atmospheric oxidation reaction of CH3CH(OCH3)CHF2 with the BrO radical proceeded in four (4) plausible reaction routes. The total experimental rate of 4.34*10-06 cm-3 molecule-1 sec-1 for HFE + BrO reaction was estimated with atmospheric lifetime (ALT)/global warming potential (GWP) of 1.80 years and 165.30 respectively. The 3D potential energy surfaces (PES) for the reaction was however constructed at absolute temperature of 298.15 K.
... Recent researches have shown that chlorofluorocarbons (CFCs) which are used for aerosols: deodorant sprays, paint sprays, furniture polishes and refrigerators pose direct environmental threats on ozone (O 3 ) by diffusing into O 3 layer and thus deplete it at a rate faster than it can be replaced in the atmosphere (Garfield, 1988;Hurley et al., 2004;Rohrer and Berresheim, 2006;Papadimitriou et al., 2007, Yang et al., 2007WMO, 2010;Mendes et al., 2014;Baidya et al., 2017). As a result, international restrictions and warning was placed on the usage of CFCs as agreed upon in the Montreal Protocol (Good et al., 1998;Lelieveld et al., 2002;Ye at al., 2016;Kovacevic and Sabljic, 2017). Instead, alternative chemicals which cannot pose or with less posing ability on ozone is recommended as substantial substitutes for the CFCs (Espinosa-Garcia, 2003;Furin, 2006;Galano et al., 2010;Carr et al., 2013;Li et al., 2014). ...
The knowledge of atmospheric chemistry has explained several reactions that occur in atmosphere regarding volatile organic compounds (VOCs). In this original paper, computational kinetic study was carried out on atmospheric oxidation reaction mechanism of 1-fluoro-2-methoxypropane (CH3CH(OCH3)CFH2) with OH/ClO radicals using DFT/M06-2X/6–311++G∗∗ method. To improve the results, DFT/M06-2X/6–311++G(2df,2p) single-point calculations were performed on the reacting species involved. The Monte Carlo search on the investigating hydrofluoroether (H3CCH(OCH3)CFH2) showed nine conformers with the lowest global minimum conformer being considered for this study. The reaction proceeded via four (4) reaction routes which led to dehydrogenation in each cases of the radical (OH/ClO) used. The total rate for dehydrogenation reaction of H3CCH(OCH3)CFH2 with OH/ClO radicals is 9.13 ∗ 10³ s⁻¹ and 1.23 ∗ 10⁶ s⁻¹ at 298 K which is in agreement with the available experimental rates recorded by Healthfield et al. (1998), Kazuaki Tokuhashi et al. (2000). Also, in each radical cases, thermodynamics parameters, the major and minor products’ heat of formation were computed with potential energy surfaces (PES) for the reactions constructed at absolute temperature of 298 K.
... The atmospheric lifetime of HCEs is mainly governed by its reaction with OH radical due to its high concentration in atmosphere and reaction with Cl atom in the coastal areas. In contemporary times, theoretical and experimental studies of the reaction of HCEs commenced by Cl atoms and OH radicals is numerous [7][8][9][10][11][12]. For the reaction of HCEs commenced by NO 3 radical has been identified and average concentration value is ascertained by long path spectroscopic techniques. ...
... The name semiempirical molecular orbital theory indicates that the methods applied have been parameterized to rehabilitate experimental data (Ye et al. 2016). Semiempirical techniques use the same Linear Combination of Atomic Orbitals-Self Consistent Field (LCAO-SCF) theory as ab initio programs (Lewars 2016). ...
Recently, pharmaceutically active compounds including antibiotics have been detected in drinking water at very low levels, mostly nanogram/liter concentrations, proposing that these materials were unaffected by water treatment processes. Adsorption processes were suggested to play a significant role in the removal of antibiotics. In this study, the adsorption behavior of doxycycline (DC) in aqueous solution was evaluated. The four factors influencing the adsorption of DC onto graphene nanosheet (GNS) were studied. The results showed that initial pH ∼ 6 to 7 and contact time ∼ 200 min are optimum. The monolayer adsorption capacity was reduced with the increasing temperature from 25 to 45 °C. Nonlinear regressions were carried out to define the best fit model for every system. Among various models, the Hill isotherm model represented the equilibrium adsorption data of antibiotics while the kinetic data were well fitted by the Elovich kinetic model. The maximum adsorption capacity (qmax) was 110 mg.g⁻¹, obtained from the Hill equation. Semiempirical molecular orbital theory was used to investigate the molecular interaction of the adsorption system. The experiments and semiempirical computation have systematically demonstrated that DC could be adsorbed onto GNS by π- π and electrostatic interactions. It was shown that there is a good compromise with the experimental results.
Graphical abstractInsights into doxycycline adsorption onto graphene nanosheet: quantum mechanics, thermodynamics, and kinetic study.
The mechanism and dynamics of CHF2CF2OCHF2 initiated by OH radical evaluated through the density functional theory and variflex code. The solvation pattern of PCM was utilized to analyze the influence of water on the CHF2CF2OCHF2 + OH reaction. The most feasible reaction channel is resulting in the product CF2CF2OCHF2 with H2O by hydrogen abstraction. The computed rate coefficient is consistent with the experimental data. The results turned out that aqueous water act as a disincentive to the title reaction. In the atmosphere, the computation results testified that OH, H2O, NH3 and HCOOH could not accelerate the degradation of the CHF2CF2OCHF2 through OH-initiated in view of the Gibbs free barriers. The research of the follow-up oxidation procedure of the products CHF2CF2OCF2 and CF2CF2OCHF2 with O2/NO reactions indicated that CF2O and CHF2 were the most feasible products. The atmospheric lifetimes of CHF2CF2OCHF2 were in the scope of 71.10-4.74 years in altitude of 0-12 km and at 200-300 K. This research supplies discernment into the conversion of CHF2CF2OCHF2 in a complex environment.
The energetics, thermochemistry and kinetics for the reaction between n-butyl peroxy radical and HO2 radical was computed using CCSD(T)/aug-cc-pVDZ// B3LYP/6-311G(d,p) level of theory coupled with Canonical Variational Transition state theory incorporating small curvature tunnelling corrections. The H abstraction pathway involving addition-elimination mechanism on the triplet energy surface was found to be most feasible reaction pathway. The calculated rate coefficients showed a negative temperature dependency in the studied range of 200 to 400 K. The Arrhenius expression for the title reaction was derived as, ktotal = 1.35 × 10⁻¹⁶ exp(3703/T) cm³molecule⁻¹s⁻¹.
