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1.
Spectrochim Acta A Mol Biomol Spectrosc ; 206: 104-111, 2019 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-30099310

RESUMO

The potential energy surface for the reaction of O(3P) with CH2 = CHCH2F has been studied at the CCSD(T)//M06-2X level of theory. Three different reaction entrances were revealed, namely, terminal-C addition, central-C addition, and H(or F)-abstraction, leading to CH2OCHCH2F (IM1), CH2CHOCH2F (IM2) and HO + C3H4I (OF + C3H5), respectively. The corresponding activation barriers are 3.04 (TS1), 3.71 (TS2), 7.06 (h-TS1), 12.68 (h-TS2), 14.04 (h-TS3) and 63.58 kcal/mol (F-TS1) kcal/mol. Several conceivable decomposition and isomerization channels were also examined for IM1 and IM2. The total and individual rate constants were calculated by using Multichannel RRKM and TST theory over a wide range of temperatures (200-3000 K) and pressures(10-14-1014 Torr).The branching ratios indicate that IM1 is the major product at 200-800 K. The production of P1 (CH2FCHCHO + H)via H-elimination from IM1 becomes dominant at high temperatures.

2.
Environ Sci Pollut Res Int ; 25(25): 24939-24950, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29931646

RESUMO

The hydroxyl radical, as the most important oxidant, controls the removal of some volatile organic compounds (VOCs) in the atmosphere. In this work, the atmospheric oxidation processes of acrylic acid by OH radical have been investigated by density functional theory (DFT). The energetic routes of the reaction of CH2CHCOOH with OH radical have been calculated accurately at the CCSD(T)/cc-pVTZ//M06-2X/6-311++G(d,p) level. It is implicated that the oxidation has five elementary reaction pathways mostly hinging on how hydroxyl radical approaches to the carbon skeleton of acrylic acid. The atmospheric degradation mechanisms of the CH2CHCOOH by OH radical are the formation of reactive intermediates IM1 and IM2. Meanwhile, the further oxidation mechanisms of IM1 and IM2 by O3 and NO are also investigated. The rate coefficients have been computed using tight transition state theory of the variflex code. The calculated rate coefficient is 2.3 × 10-11 cm3 molecule-1 s-1 at standard pressure and 298 K, which is very close to the laboratory data (1.75 ± 0.47 × 10-11 cm3 molecule-1 s-1). Moreover, the atmospheric lifetime of acrylic acid is about 6 h at 298 K and 1 atm, implying that the fast sinks of acrylic acid by hydroxyl radical.


Assuntos
Acrilatos/química , Atmosfera/química , Radical Hidroxila/química , Teoria Quântica , Cinética , Oxirredução
3.
J Mol Graph Model ; 76: 512-520, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28735893

RESUMO

Singlet and triplet potential energy surfaces for the CH3O2 with I reaction have been investigated computationally to propose the reaction mechanisms and possible products. Multichannel RRKM theory and transition-state theory have been used to compute the overall and individual rate constants at 200-3000K and 10-14-1014Torr. On the singlet PES, addition-elimination, substitution and H-abstraction mechanisms are located, and the addition-elimination mechanism is dominant. At 70Torr with N2 as bath gas, IM1(CH3OOI) formed by collisional stabilization is dominated at 200-300K, whereas CH2O and HIO are the major products at the temperatures between 350 and 3000K; The title reaction exhibits the typical falloff behavior. The results show that temperature and pressure affect the yield of products. Furthermore, the predicted rate constants at 298K 70Torr of N2 agree well with the available experimental values. On the triplet PES, the most favorable product should be CH3I+O2(3Σ) at atmospheric condition. Other two pathways on the triplet PES will not compete with the pathways on the singlet PES in kinetically and thermodynamically.


Assuntos
Radical Hidroxila/química , Iodo/química , Modelos Teóricos , Algoritmos , Cinética , Modelos Moleculares
4.
Chemosphere ; 150: 329-340, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26921586

RESUMO

Singlet and triplet potential energy surfaces for the atmospheric ozonation of trans-2-chlorovnyldichloroarsine (lewisite) are investigated theoretically. Optimizations of the reactants, products, intermediates and transition states are carried out at the BHandHLYP/6-311+G(d,p) level. Single point energy calculations are performed at the CCSD(T)/6-311+G(d,p) level based on the optimized structures. The detailed mechanism is presented and discussed. Various possible H (or Cl)-abstraction and C (or As)-addition/elimination pathways are considered. The results show that the As-addition/elimination is more energetically favorable than the other mechanisms. Rice-Ramsperger-Kassel-Marcus (RRKM) theory is used to compute the rate constants over the possible atmospheric temperature range of 200-3000 K and the pressure range of 10(-8)-10(9) Torr. The calculated rate constant is in good agreement with the available experimental data. The total rate coefficient shows positive temperature dependence and pressure independence. The modified three-parameter Arrhenius expressions for the total rate coefficient and individual rate coefficients are represented. Calculation results show that major product is CHClCHAs(OOO)Cl2 (s-IM3) at the temperature below 600 K and O2 + CHClCHAsOCl2 (s-P9) play an important role at the temperature between 600 and 3000 K. Time-dependent DFT (TD-DFT) calculations indicate that CHCl(OOO)CHAsCl2 (s-IM3) and CHOAsCl2 (s-P5) can take photolysis easily in the sunlight. Due to the absence of spectral information for arsenide, computational vibrational spectra of the important intermediates and products are also analyzed to provide valuable evidence for subsequent experimental identification.


Assuntos
Poluentes Atmosféricos/análise , Arsenicais/análise , Substâncias para a Guerra Química/análise , Modelos Teóricos , Ozônio/química , Poluentes Atmosféricos/química , Poluentes Atmosféricos/efeitos da radiação , Arsenicais/química , Arsenicais/efeitos da radiação , Substâncias para a Guerra Química/química , Substâncias para a Guerra Química/efeitos da radiação , Cinética , Fotólise , Pressão , Temperatura Ambiente
5.
Chemosphere ; 111: 545-53, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24997964

RESUMO

Mechanisms for the atmospheric degradation reaction of BrCH2O2+HO2 were investigated using quantum chemistry methods. The result indicates that the dominant product is BrCH2OOH+O2((3)Σ). While CH2O+HBr+O3, BrCHO+OH+HO2 and CH2O+Br+HO3 will be competitive to a certain extent in the atmosphere. Meanwhile, the nascent product - BrCH2OOH reacts easily with OH radicals leading to BrCH2O2 again under the atmospheric conditions. Moreover, OH radicals could act as a catalyst in the net reaction of BrCH2OOH→BrCHO+H2O. Thus the proposed product BrCHO+H2O+O2 in the experiment might be generated from the subsequent reaction of BrCH2OOH with extra OH radicals. Comparisons indicate that halogen substitution effect makes minor contributions to the XCH2O2 (X=H, F, Cl and Br)+HO2 reactions in the atmosphere.


Assuntos
Atmosfera/química , Hidrocarbonetos Bromados/química , Radical Hidroxila/química , Modelos Moleculares , Oxigênio/química , Água/química
6.
J Comput Chem ; 35(22): 1646-56, 2014 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-24995629

RESUMO

The reaction of propargyl alcohol with hydroxyl radical has been studied extensively at CCSD(T)/aug-cc-pVTZ//MP2/cc-pVTZ level. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for this important reaction in detail. Two reaction mechanisms were revealed, namely addition/elimination and hydrogen abstraction mechanism. The reaction mechanism confirms that OH addition to C≡C triple bond forms the chemically activated adducts, IM1 (·CHCOHCH2OH) and IM2 (CHOH·CCH2OH), and the hydrogen abstraction pathways (-CH2OH bonded to the carbon atom and alcohol hydrogen) may occur via low barriers. Harmonic model of Rice-Ramsperger-Kassel-Marcus theory and variational transition state theory are used to calculate the overall and individual rate constants over a wide range of temperatures and pressures. The calculated rate constants are in good agreement with the experimental data. At atmospheric pressure with Ar as bath gas, IM1 (·CHCOHCH2OH) and IM2 (CHOH·CCH2OH) formed by collisional stabilization are dominant in the low temperature range. The production of CHCCHOH + H2O via hydrogen abstraction becomes dominate at higher temperature. The fraction of IM3 (CH2COHCH2·O) is very significant over the moderate temperature range.


Assuntos
Alquinos/química , Gases/química , Radical Hidroxila/química , Modelos Químicos , Propanóis/química
7.
J Mol Model ; 20(7): 2335, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25007917

RESUMO

The trans-2-chlorovinyldichloroarsine (Lewisite) was produced and handled during WWI and WWII as chemical warfare agents. It was very difficult to explore its chemical characterization by experiments ways. The quantum chemical calculations proved to be a precise and harmless method for the toxicological system. In this paper, the gas phase reaction mechanisms of OH radical with trans-2-chlorovinyldichloroarsine (lewisite) were studied by second-order Møller-Plesset perturbation theory (MP2) method. The geometries of reactants, products, complexes, and transition states were optimized at the MP2/6-311++G(d,p) level. To gain more accurate mechanistic knowledge, the single-point energies were calculated using G3 and CCSD(T) method. This reaction exhibited three mechanisms, namely, direct hydrogen abstraction, direct chlorine abstraction, and addition/elimination. Multichannel Rice-Ramsperger-Kassel-Marcus theory and transition-state theory have been carried out for overall and individual rate constants over a wide range of temperatures and pressures. The computational results indicated that addition/elimination reaction is more favorable than direct hydrogen abstraction and direct chlorine abstraction. The major products for the total reaction are AsCl2 and CHClCH2O generated via C(2)-addition/elimination.

8.
J Chem Phys ; 140(8): 084309, 2014 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-24588171

RESUMO

The reaction of allyl chloride with the hydroxyl radical has been investigated on a sound theoretical basis. This is the first time to gain a conclusive insight into the reaction mechanism and kinetics for important pathways in detail. The reaction mechanism confirms that OH addition to the C=C double bond forms the chemically activated adducts, IM1 (CH2CHOHCH2Cl) and IM2 (CH2OHCHCH2Cl) via low barriers, and direct H-abstraction paths may also occur. Variational transition state model and multichannel RRKM theory are employed to calculate the temperature-, pressure-dependent rate constants. The calculated rate constants are in good agreement with the experimental data. At 100 Torr with He as bath gas, IM6 formed by collisional stabilization is the major products in the temperature range 200-600 K; the production of CH2CHCHCl via hydrogen abstractions becomes dominant at high temperatures (600-3000 K).


Assuntos
Compostos Alílicos/química , Gases/química , Radical Hidroxila/química , Teoria Quântica , Pressão , Temperatura Ambiente
9.
J Mol Graph Model ; 48: 18-27, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24366002

RESUMO

Potential energy surface for the reaction of hydroxyl radical (OH) with 3-fluoropropene (CH2CHCH2F) has been studied to evaluate the reaction mechanisms, possible products and rate constants. It has been shown that the CH2CHCH2F with OH reaction takes place via a barrierless addition/elimination and hydrogen abstraction mechanism. It is revealed for the first time that the initial step for the barrierless additional process involves a pre-reactive loosely bound complex (CR1) that is 1.60 kcal/mol below the energy of the reactants. Subsequently, the reaction bifurcates into two different pathways to form IM1 (CH2CHOHCH2F) and IM2 (CH2OHCHCH2F), which can decompose or isomerize to various products via complicated mechanisms. Variational transition state model and multichannel RRKM theory are employed to calculate the temperature-, pressure-dependent rate constants and branching ratios. At atmospheric pressure with He as bath gas, IM1 formed by collisional stabilization is dominated at T≤600 K; whereas the direct hydrogen abstraction leading to CH2CHCHF and H2O are the major products at temperatures between 600 and 3000 K, with estimated contribution of 72.9% at 1000 K. Furthermore, the predicted rate constants are in good agreement with the available experimental values.


Assuntos
Alcanos/química , Hidrocarbonetos Fluorados/química , Radical Hidroxila/química , Simulação por Computador , Cinética , Modelos Químicos , Modelos Moleculares , Termodinâmica
10.
J Phys Chem A ; 117(30): 6629-40, 2013 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-23865514

RESUMO

The complex potential energy surface of allyl alcohol (CH2CHCH2OH) with hydroxyl radical (OH) has been investigated at the G3(MP2)//MP2/6-311++G(d,p) level. On the surface, two kinds of pathways are revealed, namely, direct hydrogen abstraction and addition/elimination. Rice-Ramsperger-Kassel-Marcus theory and transition state theory are carried out to calculate the total and individual rate constants over a wide temperature and pressure region with tunneling correction. It is predicted that CH2CHOHCH2OH (IM1) formed by collisional stabilization is dominate in the temperature range (200-440 K) at atmospheric pressure with N2 (200-315 K at 10 Torr Ar and 100 Torr He). The production of CH2CHCHOH + H2O via direct hydrogen abstraction becomes dominate at higher temperature. The kinetic isotope effect (KIE) has also been calculated for the title reaction. Moreover, the calculated rate constants and KIE are in good agreement with the experimental data.


Assuntos
Gases/química , Hidrogênio/química , Radical Hidroxila/química , Modelos Químicos , Propanóis/química , Pressão Atmosférica , Simulação por Computador , Cinética , Temperatura Ambiente , Termodinâmica
11.
J Phys Chem A ; 116(12): 3172-81, 2012 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-22385279

RESUMO

The potential energy surfaces of the CF(3)CH═CH(2) + OH reaction have been investigated at the BMC-CCSD level based on the geometric parameters optimized at the MP2/6-311++G(d,p) level. Various possible H (or F)-abstraction and addition/elimination pathways are considered. Temperature- and pressure-dependent rate constants have been determined using Rice-Ramsperger-Kassel-Marcus theory with tunneling correction. It is shown that IM1 (CF(3)CHCH(2)OH) and IM2 (CF(3)CHOHCH(2)) formed by collisional stabilization are major products at 100 Torr pressure of Ar and in the temperature range of T < 700 K (at P = 700 Torr with N(2) as bath gas, T ≤ 900 K), whereas CH(2)═CHOH and CF(3) produced by the addition/elimination pathway are the dominant end products at 700-2000 K. The production of CF(3)CHCH and CF(3)CCH(2) produced by hydrogen abstractions become important at T ≥ 2000 K. The calculated results are in good agreement with available experimental data. The present theoretical study is helpful for the understanding the characteristics of the reaction of CF(3)CH═CH(2) + OH.

12.
Phys Chem Chem Phys ; 12(36): 10846-56, 2010 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-20657941

RESUMO

Singlet and triplet potential energy surfaces for the reactions of oxygen atoms ((3)P and (1)D) with CF(3)CN have been studied computationally to evaluate the reaction mechanisms, possible products, and rate constants. On the triplet surface, six kinds of pathway are revealed, namely: direct fluorine abstraction, C-addition/elimination, N-addition/elimination, substitution, insertion and F-migration. The results show that the reaction should occur mainly through the C-addition/elimination mechanism involving the chemically activated CF(3)C(O)N* intermediate, and the major products are CF(3) and NCO. The rate constants for C-addition/elimination channel of the reaction of O((3)P) with CF(3)CN have been determined by using RRKM statistical rate theory and compared with the experimental data. On the singlet surface, the atomic oxygen can easily insert into the C-F or C-C bond of CF(3)CN, forming the insertion intermediates FOCF(2)CN and CF(3)OCN, and O((1)D) can add to the carbon or nitrogen atom of the CN group in CF(3)CN, forming the addition intermediates CF(3)C(O)N and CF(3)CNO; both approaches are found to be barrierless. The decomposition and isomerization of some intermediates were also modeled at the QCISD(T)/6-311+G(2df)//B3LYP/6-311+G(d) level for the better understanding of the O((1)D) with CF(3)CN chemistry. The decomposition products CF(3) and NCO arising from CF(3)OCN and CF(3)NCO are the dominant species. Further comparison with similar reactions is also summarized.

13.
J Phys Chem A ; 114(10): 3516-22, 2010 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-20175584

RESUMO

Both singlet and triplet potential energy surfaces for the reaction of ground-state formaldehyde (CH(2)O) and ozone (O(3)) are theoretically investigated at the BMC-CCSD//BHandHLYP/6-311+G(d,p) level. Various possible isomerization and dissociation pathways are probed. Hydrogen abstraction, oxygen abstraction, and C-addition/elimination are found on both the singlet and the triplet surfaces. The major products for the total reaction are HCO and HOOO, which are generated via hydrogen abstraction. The transition state theory (TST) and multichannel RRKM calculations have been carried out for the total and individual rate constants for determinant channels over a wide range of temperatures and pressures.

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