MECHANISM AND KINETICS OF THE CH3CH2C(O)OCH2CH3 + OH REACTION: A THEORETICAL STUDY

2011 ◽  
Vol 10 (05) ◽  
pp. 691-709 ◽  
Author(s):  
CONG HOU ◽  
CHENG-GANG CI ◽  
TONG-YIN JIN ◽  
YONG-XIA WANG ◽  
JING-YAO LIUM
Keyword(s):  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Negative Temperature ◽  
State Theory ◽  
Measured Temperature ◽  
Temperature Range ◽  
Global Rate ◽  
Abstraction Reaction ◽  
Lower Temperature ◽  
Kinetic Calculations

The hydrogen abstraction reaction of CH 3 CH 2 C(O)OCH 2 CH 3 + OH has been studied theoretically by dual-level direct dynamics method. Six H-abstraction channels were found for this reaction. The required potential energy surface information for the kinetic calculations was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants were calculated by the improved canonical variational transition-state theory with small-curvature tunneling correction (ICVT/SCT) approach in the temperature range of 200–2000 K. It is shown that the "methylene H-abstraction" from the alkoxy end of the ester CH 3 CH 2 C(O)OCH 2 CH 3 is the dominant channel at lower temperature (< 400 K), while the other channels from the acetyl end should be taken into account as the temperature increases and become the competitive ones at higher temperature. The calculated global rate constants are in good agreement with the experimental ones in the measured temperature range and exhibit a negative temperature dependence below 500 K. A four-parameter rate constant expression was fitted from the calculated kinetic data between 200–2000 K.

scholarly journals Theoretical Kinetics Study Of The HO2 + C2H5OH Hydrogen Abstraction Reaction

2020 ◽  
Vol 36 (1) ◽  
Author(s):  
Nguyen Trong Nghia
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
Hydrogen Abstraction ◽  
Branching Ratios ◽  
State Theory ◽  
Kinetics Study ◽  
Abstraction Reaction ◽  
Hydrogen Abstraction Reaction ◽  
Ho2 Radical

C2H5OH has been using as an alternative fuel for decades; HO2 also plays a pivotal role in the combustion. The kinetics and mechanism for the reaction between C2H5OH and HO2 radical has been investigated using the molecular parameters for the reactants, transition states and products predicted at the CCSD(T)//B3LYP/6-311++G(3df,2p) level of theory. There are ten pair products have been found including C2H5O + H2O2 (PR1), CH3CHOH + H2O2 (PR2), CH2CH2OH + H2O2 (PR3), CH3CH2OOOH + H (PR4), C2H5 + HOOOH (PR5), CH3CH2OOH + OH (PR6), CH3CH(OH)OOH + H (PR7), HOCH2CH2OH + H (PR8), HOOCH3 + CH2OH (PR9), and CH3 + HOOCH2OH (PR10) in which the second and third ones are the major channels. The rate constants and branching ratios for all H-abstraction reactions have been calculated using the conventional transition state theory with asymmetric Eckart tunneling corrections for the temperature ranging from 298 to 2000 K.

AB INITIO CALCULATIONS AND KINETICS STUDY FOR THE DIRECT HYDROGEN ABSTRACTION REACTION OF HYDROGEN SELENIDE WITH HYDROGEN ATOM

2011 ◽  
Vol 10 (05) ◽  
pp. 629-639
Author(s):  
YUE ZHANG
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
Hydrogen Abstraction ◽  
State Theory ◽  
Forward Rate ◽  
Variational Transition State Theory ◽  
Abstraction Reaction ◽  
Hydrogen Abstraction Reaction ◽  
Good Agreement

We present a direct ab initio dynamics study of thermal rate constants of the hydrogen abstraction reaction of H 2 Se + H → SeH + H 2. The QCISD and CCSD(T) methods were employed to optimize the geometries of stationary points and to calculate the harmonic vibrational frequencies. The split-valence 6-311 + G(d,p) and correlation-consistent cc-pVTZ basis sets big enough to describe the geometries and vibrational frequencies of the species involving in the title reaction. The energies obtained at the QCISD(T)/6-311 ++ G(3df,3pd)//QCISD/6-311 + G(d,p) level of theory is able to compare to those calculated at the CCSD(T)/6-311 ++ G(3df,3pd)//CCSD(T)/6-311 + G(d,p) level of theory. The energies of all the selected points along the minimum energy path (MEP) were refined at the QCISD(T)/6-311 ++ G(3df,3pd) level of theory. The barriers were obtained at the both QCISD(T)/6-311 ++ G(3df,3pd)//QCISD/6-311 + G(d,p) and CCSD(T)/6-311 ++ G(3df,3pd)//CCSD(T)/6-311 + G(d,p) levels of theory are in good agreement with experimental one. The forward rate constants were evaluated with both canonical variational transition state theory with small curvature tunneling correction (CVT/SCT) and improved canonical variational transition state theory with small curvature tunneling correction (ICVT/SCT) in the temperature range of 200–2500 K. The calculated forward rate constants of the reaction at the QCISD(T)/6-311 ++ G(3df,3pd)//QCISD/6-311 + G(d,p) level of theory are in good agreement with available experimental data.

Reactions of trifluoromethyl radicals. V. Hydrogen abstraction from methyl acetate and methyl (2H3)Acetate

1980 ◽  
Vol 33 (7) ◽  
pp. 1437
Author(s):  
NL Arthur ◽  
PJ Newitt
Keyword(s):  
Isotope Effect ◽  
Rate Constants ◽  
Methoxy Group ◽  
Methyl Acetate ◽  
Kinetic Isotope Effect ◽  
Hydrogen Abstraction ◽  
Activation Energies ◽  
Temperature Range ◽  
Kinetic Isotope ◽  
Acetyl Group

Hydrogen abstraction by CF3 radicals from CH3COOCH3 and CD3COOCH3 has been studied in the temperature range 78-242°, and data have been obtained for the reactions: CF3 + CH3COOCH3 → CF3H+[C3H5O2] �������������(3) CF3 + CH3COOCH3 → CF3H+CH2COOCH3������������ (4) CF3 + CD3COOCH3 → CF3D+CD2COOCH3������������ (6) CF3 + CD3COOCH3 → CF3H+CD3COOCH2������������ (7) The corresponding rate constants, based on the value of 1013.36 cm3 mol-1 S-1 for the recombination of CF3 radicals, are given by (k in cm3 mol-1 s-1 and E in J mol-1): logk3 = (11.52�0.05)-(35430�380)/19.145T ���� (3)logk4 = (11.19�0.07)-(34680�550)/19.145T ���� (4)logk6 = (11.34�0.06)-(46490�490)/19.145T ���� (6)logk7 = (11.26�0.05)-(36440�400)/19.145T ���� (7)At 400 K, 59% of abstraction occurs from the acetyl group, and 41 % from the methoxy group. The kinetic isotope effect at 400 K for attack on the acetyl group is 25, due mainly to a difference in activation energies.

Étude théorique des réactions d'abstraction d'hydrogène , avec R, X≡H, CH3, NH2,OH et F

1985 ◽  
Vol 63 (7) ◽  
pp. 1447-1456 ◽  
Author(s):  
Georges Leroy ◽  
Michel Sana ◽  
Anne Tinant
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
Hydrogen Abstraction ◽  
State Theory ◽  
Arrhenius Behavior ◽  
Activation Barriers ◽  
Empirical Procedure ◽  
Semi Empirical ◽  
Theory And Experiment

Hydrogen abstraction reactions [Formula: see text] with R, X≡H, CH3, NH2,OH, and F have been studied at the abinitio 6-31G – UHF level. However, energetic properties were computed at the CI level. Rate constants and Arrhenius parameters have been obtained using the transition state theory formalism with Eckart's tunneling correction. The discrepancy between theoretical and experimental results led us to elaborate a semi-empirical procedure to calculate activation barriers, in which the bonds R—H and X—H are represented by Morse curves. Thus, the agreement between theory and experiment is much better. Moreover, the results obtained by this procedure demonstrate the non-Arrhenius behavior of all the reactions under consideration and allow us to rationalize a large number of experimental facts.

The Mercury-Sensitized Photolysis of Pentamethyldisilane

1996 ◽  
Vol 51 (1-2) ◽  
pp. 105-115 ◽  
Author(s):  
C. Kerst ◽  
P. Potzinger ◽  
H. Gg. Wagner
Keyword(s):  
Quantum Yield ◽  
Rate Constants ◽  
Hydrogen Abstraction ◽  
Branching Ratios ◽  
Bond Breaking ◽  
Hydrogen Atoms ◽  
Substitution Reactions ◽  
Abstraction Reaction

Abstract Two primary processes were observed in the Hg-sensitized photolysis of Me 5 Si 2 H: (I) hydrogen abstraction from the Si-H bond with a quantum yield of 0(1) = 0.85, (V) Si-Si bond breaking with 0(V) = 0.04. The hydrogen atoms formed in (/) undergo an H atom abstraction reaction (k(3)), as well as substitution reactions at the Si centers resulting in the formation of dimethylsilane and trimethylsilyl radical (k(4)) or trimethylsilane and dimethylsilyl radical (k(5)). The following branching ratios have been determined:[xxx]The ratio of disproportionation (k(2)) to combination (k(1)) for the pentamethyldisilyl radical has been determined with MeOH as the scavenger for 1-methyl-l-trimethylsilylsilene, 0.046 < k(2)/A: C1) < 0.071. A mechanism with pertinent rate constants has been proposed which accounts for theresults.

scholarly journals Predicting pressure-dependent unimolecular rate constants using variational transition state theory with multidimensional tunneling combined with system-specific quantum RRK theory: a definitive test for fluoroform dissociation

2016 ◽  
Vol 18 (25) ◽  
pp. 16659-16670 ◽  
Author(s):  
Junwei Lucas Bao ◽  
Xin Zhang ◽  
Donald G. Truhlar
Keyword(s):  
Experimental Data ◽  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
State Theory ◽  
Variational Transition State Theory ◽  
Temperature Range ◽  
Multidimensional Tunneling ◽  
Specific Quantum ◽  
Wide Pressure

We show that rate constants for dissociation of fluoroform computed by VTST/SS-QRRK agree excellently with definitive experimental data over a wide pressure and temperature range.

Hydrogen abstraction from (2H3)methyl acetate by methyl and trifluoromethyl radicals

1981 ◽  
Vol 34 (4) ◽  
pp. 727 ◽  
Author(s):  
NL Arthur ◽  
PJ Newitt
Keyword(s):  
Rate Constants ◽  
Methoxy Group ◽  
Methyl Acetate ◽  
Isotope Effects ◽  
Hydrogen Abstraction ◽  
Kinetic Isotope Effects ◽  
Temperature Range ◽  
Kinetic Isotope ◽  
Acetyl Group

A study of hydrogen abstraction from CH3COOCD3 by CH3 radicals in the temperature range 113-232�, and by CF3 radicals in the range 83-212�, has yielded data on the reactions: CH3+CH3COOCD3 → CH4+CH2COOCD3 (1)CH3+CH3COOCD3 → CH3D+CH3COOCD2 (2) CF3+CH3COOCD3 → CF3H+CH2COOCD2 (3) CF3+CH3COOCD3 → CF3D+CH3COOCD2 (4) The corresponding rate constants, based on the values 1013.34 and 1013.36 cm3 mol-1 s-1 for the recombination of CH3 and CF3 radicals, respectively, are given by (k in cm3 mol-1 s-1 and E in J mol-1): logk1 = (11.31�0.12)-(43500�1030)/19.145T (1) logk1 = (11.31�0.12)-(53460�640)/19.145t (2) logk3 = (11.12�0.06)=(34260�450)/19.145T � (3) logk4 =(10.93�0.12)-(38650�900)/19.145T (4)These results lead to kinetic isotope effects at 400 K for attack on the acetyl group of 11, for the CH3 reaction, and 24, for the CF3 reaction, thus confirming the values we obtained previously. For attack on the methoxy group, the kinetic isotope effects are 8 and 4, for the CH3 and CF3 reactions, respectively.

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