scholarly journals Kinetics of the Reaction of Methyl Radical with Methanol

2018 ◽  
Vol 34 (1) ◽  
Author(s):  
Nguyen Huu Tho ◽  
Nguyen Xuan Sang
Keyword(s):  
Physical Chemistry ◽  
Shock Tube ◽  
Ab Initio ◽  
Density Functional ◽  
Chemical Society ◽  
Chemical Physics ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Orbital Theory ◽  
Kinetics Of

This work studied theoretically in details the mechanism, kinetics and thermochemistry of reactions of methyl radical with methanol. The theoretical study was carried out by ab initio molecular orbital theory based on CCSD(T)/B3LYP/6-311++G(3df,2p) methods in conjunction variational transition state theory (VTST). Calculated results showed that, in the temperature range from 300K to 2000K, and the pressure at 760 Torr, temperature dependent rate constants of the reactions were: CH3 + CH3OH ® CH4 + CH2OH    k(T) = 2.146´10-27.T4.64.exp(-33.47[kJ/mol/RT), CH3 + CH3OH ® CH4 + CH3O       k(T) = 2.583´10-27.T4.52.exp(-29.56[kJ/mol/RT), CH3 + CH3OH ® H + CH3OCH3    k(T) = 1.025´10-23.T3.16.exp(-186.84[kJ/mol/RT) When the reaction temperature is above 730 K, the abstraction process of H in –CH3 group of methanol will occur faster. The abstraction process of H in –OH group dominates when the reaction temperature is below 730 K. Keywords Kinetic, methyl, methanol, ab initio References 1. Slagle, I.R., D. Sarzynski, and D. Gutman, Kinetics of the reaction between methyl radicals and oxygen atoms between 294 and 900 K. The Journal of Physical Chemistry, 1987. 91(16): p. 4375-4379.2. Rutz L., B.H., Bozzelli J. W., Methyl Radical and Shift Reactions with Aliphatic and Aromatic Hydrocarbons: Thermochemical Properties, Reaction Paths and Kinetic Parameters. American Chemical Society, Division Fuel Chemistry, 2004. 49(1): p. 451-452.3. Johnson, D.G., M.A. Blitz, and P.W. Seakins, The reaction of methylidene (CH) with methanol isotopomers. Physical Chemistry Chemical Physics, 2000. 2(11): p. 2549-2553.4. Cribb, P.H., J.E. Dove, and S. Yamazaki, A kinetic study of the pyrolysis of methanol using shock tube and computer simulation techniques. Combustion and Flame, 1992. 88(2): p. 169-185.5. Dombrowsky, C., et al., An Investigation of the Methanol Decomposition Behind Incident Shock Waves. Berichte der Bunsengesellschaft für physikalische Chemie, 1991. 95(12): p. 1685-1687.6. Krasnoperov, L.N. and J.V. Michael, High-Temperature Shock Tube Studies Using Multipass Absorption:  Rate Constant Results for OH + CH3, OH + CH2, and the Dissociation of CH3OH. The Journal of Physical Chemistry A, 2004. 108(40): p. 8317-8323.7. Shannon, T.W. and A.G. Harrison, The reaction of methyl radicals with methyl alcohol. Canadian Journal of Chemistry, 1963. 41(10): p. 2455-2461.8. Jodkowski, J.T., et al., Theoretical Study of the Kinetics of the Hydrogen Abstraction from Methanol. 3. Reaction of Methanol with Hydrogen Atom, Methyl, and Hydroxyl Radicals. The Journal of Physical Chemistry A, 1999. 103(19): p. 3750-3765.9. Alecu, I.M. and D.G. Truhlar, Computational Study of the Reactions of Methanol with the Hydroperoxyl and Methyl Radicals. 2. Accurate Thermal Rate Constants. The Journal of Physical Chemistry A, 2011. 115(51): p. 14599-14611.10. Peukert, S.L. and J.V. Michael, High-Temperature Shock Tube and Modeling Studies on the Reactions of Methanol with D-Atoms and CH3-Radicals. The Journal of Physical Chemistry A, 2013. 117(40): p. 10186-10195.11. Anastasi, C. and D.U. Hancock, Reaction of CH3 radicals with methanol in the range 525 <T/K < 603. Journal of the Chemical Society, Faraday Transactions, 1990. 86(14): p. 2553-2555.12. Dombrowsky, C. and H.G. Wagner, An investigation of the reaction between CH3 radicals and methanol at high temperatures. Berichte der Bunsengesellschaft für physikalische Chemie, 1989. 93(5): p. 633-637.13. Tsang, W., Chemical Kinetic Data Base for Combustion Chemistry. Part 2. Methanol. Journal of Physical and Chemical Reference Data, 1987. 16(3): p. 471-508.14. Becke, A.D., Density‐functional thermochemistry. II. The effect of the Perdew–Wang generalized‐gradient correlation correction. The Journal of Chemical Physics, 1992. 97(12): p. 9173-9177.15. Becke, A.D., Density‐functional thermochemistry. I. The effect of the exchange‐only gradient correction. The Journal of Chemical Physics, 1992. 96(3): p. 2155-2160.16. Becke, A.D., Density‐functional thermochemistry. III. The role of exact exchange. The Journal of Chemical Physics, 1993. 98(7): p. 5648-5652.17. Yang, W., R.G. Parr, and C. Lee, Various functionals for the kinetic energy density of an atom or molecule. Physical Review A, 1986. 34(6): p. 4586-4590.18. Hehre W. , R.L., Schleyer P. V. R. , and Pople J. A. and 30, Ab Initio Molecular Orbital Theory. 1986, New York: Wiley.19. Andersson, M.P. and P. Uvdal, New Scale Factors for Harmonic Vibrational Frequencies Using the B3LYP Density Functional Method with the Triple-ζ Basis Set 6-311+G(d,p). The Journal of Physical Chemistry A, 2005. 109(12): p. 2937-2941.20. Raghavachari, K., et al., A fifth-order perturbation comparison of electron correlation theories. Chemical Physics Letters, 1989. 157(6): p. 479-483.21. M.J. Frisch, G.W.T., H.B. Schlegel, et al., GAUSSIAN 09, Revision C.01, Gaussian Inc., Wallingford CT, 2010.22. Robson Wright, M., Theories of Chemical Reactions, in An Introduction to Chemical Kinetics. 2005, John Wiley & Sons, Ltd. p. 99-164.23. Goos, E.B., A.; Ruscic, B., Extended Third Millennium Ideal Gas and Condensed Phase Thermochemical Database for Combustion with Updates from Active Thermochemical Tables. http://garfield.chem.elte.hu/Burcat/burcat.html, October, 2017.

scholarly journals Theoretical Study of the Formation Methane in the Reaction of Methyl Radical with Propanol-2

2018 ◽  
Vol 34 (3) ◽  
Author(s):  
Nguyen Huu Tho ◽  
Nguyen Vo Hieu Liem ◽  
Nguyen Thi Huynh Nhu ◽  
Nguyen Thi Hong ◽  
Ngo Vo Thanh ◽  
...  
Keyword(s):  
Physical Chemistry ◽  
Density Functional ◽  
Theoretical Study ◽  
Polyatomic Molecules ◽  
Radical Reactions ◽  
Chemical Physics ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Reaction Paths ◽  
Kinetics Of

The reaction paths of the reaction of methyl radical with propanol-2 (i-C3H7OH) were investigated in detail using density functional theory at B3LYP/6-311++G(3df,2p) level. There were seven reaction pathways which form seven products including CH4 + (CH3)2COH, CH4 + (CH3)2CHO, CH4 + CH3CHOHCH2, CH3OH + CH3CHCH3, C2H6 + CH3CHOH, (CH3)2CH-O-CH3 + H and (CH3)3CH + OH. The results of analysis of the reaction paths and thermokinetic parameters showed that methane could be generated from three different channels. The removed H-atom from secondary carbon atom in the propanol-2 molecule is the most favorable of this reaction system. Keywords Methyl, propanol-2, B3LYP, transition state References [1] I. R. Slagle, D. Sarzyński, and D. Gutman, “Kinetics of the reaction between methyl radicals and oxygen atoms between 294 and 900 K,” Journal of Physical Chemistry, 1987.[2] L. Rutz, H. Bockhorn, and J. W. Bozzelli, “Methyl radical and shift reactions with aliphatic and aromatic hydrocarbons: Thermochemical properties, reaction paths and kinetic parameters,” in ACS Division of Fuel Chemistry, Preprints, 2004.[3] N. H. Tho and N. X. Sang, “Theoretical study of the addition and hydrogen abstraction reactions of methyl radical with formaldehyde and hydroxymethylene,” J. Serb. Chem. Soc.; OnLine First - OLF, 2018.[4] D. Ferro-Costas et al., “The Influence of Multiple Conformations and Paths on Rate Constants and Product Branching Ratios. Thermal Decomposition of 1-Propanol Radicals,” Journal of Physical Chemistry A, p. 4790−4800, 2018.[5] M. T. Holtzapple et al., “Biomass Conversion to Mixed Alcohol Fuels Using the MixAlco Process,” Applied Biochemistry and Biotechnology, 1999.[6] C. R. Shen and J. C. Liao, “Metabolic engineering of Escherichia coli for 1-butanol and 1-propanol production via the keto-acid pathways,” Metabolic Engineering, 2008.[7] A. Frassoldati et al., “An experimental and kinetic modeling study of n-propanol and iso-propanol combustion,” Combustion and Flame, vol. 157, pp. 2–16, 2010.[8] M. Z. Jacobson, “Effects of ethanol (E85) versus gasoline vehicles on cancer and mortality in the United States,” Environmental Science and Technology, 2007.[9] P. Gray and A. A. Herod, “Methyl radical reactions with ethanol and deuterated ethanols,” Transactions of the Faraday Society, 1968.[10] Z. F. Xu, J. Park, and M. C. Lin, “Thermal decomposition of ethanol. III. A computational study of the kinetics and mechanism for the CH3+C2H5OH reaction,” Journal of Chemical Physics, 2004.[11] N. H. Tho and D. T. Quang, “Nghiên cứu lý thuyết đường phản ứng của gốc metyl với etanol,” Vietnam Journal of Chemistry, vol. 56, no. 3, pp. 373–378, Jun. 2018.[12] N. H. Tho and N. X. Sang, “Kinetics of the Reaction of Methyl Radical with Methanol,” VNU Journal of Science: Natural Sciences and Technology; Vol 34 No 1DO - 10.25073/2588-1140/vnunst.4725 , Mar. 2018.[13] T. W. Shannon and A. G. Harrison, “The reaction of methyl radicals with methyl alcohol,” Canadian Journal of Chemistry, vol. 41, pp. 2455–2461, 1963.[14] S. L. Peukert and J. V. Michael, “High-temperature shock tube and modeling studies on the reactions of methanol with d-atoms and CH3-radicals,” Journal of Physical Chemistry A, 2013.[15] P. Gray and A. A. Herod, “Methyl radical reactions with isopropanol and methanol, their ethers and their deuterated derivatives,” Transactions of the Faraday Society, 1968.[16] A. D. Becke, “Density functional thermochemistry. I. The effect of the exchange only gradient correction,” Journal of Chemical Physics, vol. 96, p. 2155, 1992.[17] A. D. Becke, “Density-functional thermochemistry. II. The effect of the Perdew-Wang generalized-gradient correlation correction,” The Journal of Chemical Physics, vol. 97, p. 9173, 1992.[18] A. D. Becke, “Density-functional thermochemistry. III. The role of exact exchange,” The Journal of Chemical Physics, vol. 98, p. 5648, 1993.[19] W. Yang, R. G. Parr, and C. Lee, “Various functionals for the kinetic energy density of an atom or molecule,” Physical Review A, vol. 34 (6), pp. 4586–4590, 1986.[20] W. J. Hehre, L. Radom, P. V. R. Schleyer, and J. A. Pople, Ab Initio Molecular Orbital Theory. 1986.[21] M. P. Andersson and P. Uvdal, “New scale factors for harmonic vibrational frequencies using the B3LYP density functional method with the triple-zeta basis set 6-311+G(d,p).,” The journal of physical chemistry. A, vol. 109, pp. 2937–2941, 2005.[22] Frisch, M. J.; Trucks, G. W.; Schlegel, H.B.; Scuseria, G.E.; Robb, M.A.; Cheeseman, J. R., M. Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, J. L. Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, T. Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, and Y. . et al. Honda, “Gaussian 09 Revision C.01, Gaussian Inc. Wallingford CT.,” Gaussian 09 Revision C.01. 2010.[23] G. Herzberg, Electronic Spectra and Electronic Structure of Polyatomic Molecules. 1966.[24] L. M. Sverdlov, M. A. Kovner, and E. P. Krainov, Vibrational spectra of polyatomic molecules. New York; Chichester; Jerusalem; London: Wiley ; Israel Program for Scientific Translations, 1974.[25] E. Hirota, “Anharmonic potential function and equilibrium structure of methane,” Journal of Molecular Spectroscopy, vol. 77, pp. 213–221, 1979.[26] P. Venkateswarlu and W. Gordy, “Methyl alcohol. II. Molecular structure,” The Journal of Chemical Physics, 1955.[27] E. . B. Goos A.; Ruscic, B., “Extended Third Millennium Ideal Gas and Condensed Phase Thermochemical Database for Combustion with Updates from Active Thermochemical Tables,” http://garfield.chem.elte.hu/Burcat/burcat.html August-2018.

scholarly journals The Geometries and Stabilities of Neutral and Anionic Vanadium Doped Germanium Clusters VGen0/-( n = 9 - 13): Density Functional Theory Investigations

2019 ◽  
Vol 35 (1) ◽  
Author(s):  
Nguyen Huu Tho ◽  
Trang Thanh Tu ◽  
Trac Minh Nhan ◽  
Pham Hong Cam ◽  
Pham Thi Thi
Keyword(s):  
Physical Chemistry ◽  
Density Functional Theory ◽  
Magnetic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Physical Review ◽  
Chemical Physics ◽  
Functional Theory ◽  
Germanium Clusters ◽  
Effective Core Potentials

The geometries, stabilities of VGen0/- (n = 9 - 13) clusters were systematically studied by the density functional theory (DFT) using the BP86 functional and LANL2DZ basis set. Several possible multiplicities of each cluster were tested to determine the most stable structure among the isomers. The average binding energy per atom, fragmentation energy, second order energy difference and HOMO-LUMO gaps were evaluated. The results indicated that the neutral and anionic clusters possess higher stability when n = 10 and 12. The vertical detachment energy (VDE) and adiabatic detachment energy (ADE) were also calculated for anionic cluster to investigate their stabilities. Among neutral clusters, VGe10 had both the highest vertical ionization potential (VIP) and chemical hardness. Keywords BP86/LANL2DZ, binding energy, VGen0/- clusters, structure of clusters References [1] Shunping Shi, Yiliang Liu, Chuanyu Zhang, Banglin Deng, Gang Jiang (2015). A Computational Investigation of Aluminum-doped Germanium Clusters by Density Functional Theory Study. Computational and Theoretical Chemistry, 1054, pp. 8-15[2] Wen-Jie Zhao, Yuan-Xu Wang (2009). Geometries, stabilities, and Magnetic Properties of MnGen (n = 2 – 16) Clusters: Density-functional Theory Investigations. Journal of Molecular Structure: THEOCHEM, 901 (1–3), pp. 18-23.[3] Shi Shun-Ping, Liu Yi-Liang, Deng Bang-Lin, Zhang Chuan-Yu, and Jiang Gang (2016). Density Functional Theory Study of The Geometrical and Electronic Structures of (n = 1 - 9) clusters. World Scientific Publishing Company, 30, pp. 1750022-1750039.[4] J.Stato, H.Kobayashi, K. Ikarashi, N.Saito, H.Nishiyama, and Y. Inoue (2004). Photocatalitic Activity for Water Decomposition of RuO2-Dispersed Zn2GeO4 with d10 Configuration. The Journal of Physical Chemistry B, 108 (14), pp. 4369-4375.[5] Daoxin Dai, Molly Piels, and John E. Bowers (2014). Monolithic Germanium/Silicon Photodetectors With Decoupled Structures: Resonant APDs and UTC Photodiodes. IEEE Journal of Selected Topics in Quantum Electronics, 20 (6), pp. 3802214-3802227.[6] Chia-Yun Chou, Gyeong S. Hwang (2014). On The Origin of The Significant Difference in Lithiation Behavior Between Silicon and Germanium. Journal of Power Sources, 263, pp. 252-258.[7] Siwen Zhang, Bosi Yin, Yang Jiao, Yang Liu, Xu Zhang, Fengyu Qu, Ahmad Umar, Xiang Wu (2014). Ultra-long Germanium Oxide Nanowires: Structures and Optical Properties. Journal of Alloys and Compounds, 606, pp. 149-153.[8] T. Herrmannsdörfer, V. Heera, O. Ignatchik, M. Uhlarz, A. Mücklich, M. Posselt, H. Reuther, B. Schmidt, K.-H. Heinig, W. Skorupa, M. Voelskow, C. Wündisch, R. Skrotzki, M. Helm, and J. Wosnitza (2009).Superconducting State in a Gallium-Doped Germanium Layer at Low Temperatures. Physical Review Letters, 102, pp. 217003-217006.[9] Vijay Kumar, and Yoshiyuki Kawazoe (2002). Metal-Encapsulated Caged Clusters of Germanium with Large Gaps and Different Growth Behavior than Silicon. Physical Review Letters, 88, pp. 235504-235507.[10] Xiao-Jiao Deng, Xiang-Yu Kong, Hong-Guang Xu, Xi-Ling Xu, Gang Feng, and Wei-Jun Zheng (2015). Photoelectron Spectroscopy and Density Functional Calculations of VGen- (n = 3 − 12) Clusters. The Journal of Physical Chemistry C, 119 (20), pp. 11048-11055.[11] John P. Perdew, Kieron Burke, and Matthias Ernzerhof (1996).Generalized Gradient Approximation Made Simple. Physical Review Letters, 77, pp. 3865-3868.[12] Chaouki Siouani, Sofiane Mahtout, Sofiane Safer, and Franck Rabilloud (2017).Structure, Stability and Electronic and Magnetic Properties of VGen (n = 1 - 19) Clusters. The Journal of Physical Chemistry A, 121 (18), pp. 3540-3554.[13] Jin Wang, and Ju-Guang Han (2006).A Theoretical Study on Growth Patterns of Ni-Doped Germanium Clusters.The Journal of Physical Chemistry B, 110 (15), pp. 7820-7827.[14] Debashis Bandyopadhyay and Prasenjit Sen (2010). Density Functional Investigation of Structure and Stability of Gen and GenNi (n = 1 − 20) Clusters: Validity of the Electron Counting Rule. The Journal of Physical Chemistry A, 114 (4), pp. 1835-1842[15] Soumaia Djaadi, Kamal Eddine Aiadi, and Sofiane Mahtout (2018). Frist Principles Study of Structural, electronic and magnetic properties of (n = 1 - 17) clusters. Journal of Semiconductors, 39 (4), pp. 42001-420013.[16] İskender Muz,Mustafa Kurban,Kazım Şanlıc (2018). Analysis of the Geometrical Properties and Electronic Structure of Arsenide Doped Boron Cluster: Ab-initio approach. Inorganica Chimica Acta, 474, pp. 66-72.[17] Axel D. Becke (1988). Density-functional exchange - energy approximation with correct asymptotic behavior.Physical Review A, 38, pp. 3098-3100.[18] Willard R. Wadt, P. Jeffrey Hay (1985). Ab initio effective core potentials for molecular calculations.Potentials for main group elements Na to Bi.The Journal of Chemical Physics, 82 (1), pp. 284-298.[19] Willard R. Wadt, P. Jeffrey Hay (1985). Ab initio effective core potentials for molecular calculations.Potentials for K to Au including the outermost core orbitals.The Journal of Chemical Physics, 82 (1), pp. 299-310.[20] Willard R. Wadt, P. Jeffrey Hay (1985). Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms Sc to Hg. The Journal of Chemical Physics, 82 (1), pp. 270-283.[21] Gabriele Manca, Samia Kahla, Jean-Yves Saillard, Rémi Marchal, Jean-François Halet (2017). Small Ligated Organometallic Pdn Clusters (n = 4 - 12): A DFT Investigation. Journal of Cluster Science, 28 (2), pp. 853-868.[22] Tran Dieu Hang, Huynh Minh Hung, Lam Ngoc Thiem. Hue M. T. Nguyen (2015). Electronic structure and thermochemical properties of neutral and anionic rhodium clusters Rhn, n = 2 – 13. Evolution of structures and stabilities of binary clusters RhmM (M = Fe, Co, Ni; m = 1 – 6). Computational and Theoretical Chemistry, 1068, pp. 30–41.[23] Michael J. Frisch, et al. (2010). Gaussian 09, Revision C.01.Gaussian, Inc., Wallingford CT.

Reactions of free radicals with aromatic compounds in the gaseous phase. I. Kinetics of the reaction of methyl radicals with toluene

1964 ◽  
Vol 17 (12) ◽  
pp. 1329 ◽  
Author(s):  
MFR Mulcahy ◽  
DJ Williams ◽  
JR Wilmshurst
Keyword(s):  
Flow System ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Methyl Group ◽  
Benzyl Radical ◽  
Toluene Molecule ◽  
Benzyl Radicals ◽  
Butyl Peroxide ◽  
Kinetics Of

The kinetics of abstraction of hydrogen atoms from the methyl group of the toluene molecule by methyl radicals at 430-540�K have been determined. The methyl radicals were produced by pyrolysis of di-t-butyl peroxide in a stirred-flow system. The kinetics ,agree substantially with those obtained by previous authors using photolytic methods for generating the methyl radicals. At toluene and methyl-radical concentrations of about 5 x 10-7 and 10-11 mole cm-3 respectively the benzyl radicals resulting from the abstraction disappear almost entirely by combination with methyl radicals at the methylenic position. In this respect the benzyl radical behaves differently from the iso-electronic phenoxy radical, which previous work has shown to combine with a methyl radical mainly at ring positions. The investigation illustrates the application of stirred-flow technique to the study of the kinetics of free-radical reactions.

Homolytic Substitution at Phosphorus: An Ab initio Study of the Reaction of Hydrogen Atom and Methyl Radical With Phosphine and Methylphosphine

1995 ◽  
Vol 48 (2) ◽  
pp. 175 ◽  
Author(s):  
CH Schiesser ◽  
LM Wild
Keyword(s):  
Hydrogen Atom ◽  
Ab Initio ◽  
Phosphorus Atom ◽  
Methyl Radical ◽  
Orbital Theory ◽  
Energy Barriers ◽  
Radical Intermediates ◽  
Phosphoranyl Radical ◽  
High Level ◽  
Homolytic Substitution

Homolytic substitution reactions of hydrogen atom and methyl radical at the phosphorus atom in phosphine and methylphosphine have been examined by high-level ab initio molecular orbital theory. MP4SDTQ/6-31G**//MP2(FC)/6-31G** calculations predict that free-radical attack at the phosphorus atom in phosphines is facile, with energy barriers of 14-33 kJ mol-1 and likely to involve hypervalent phosphoranyl radical intermediates. These intermediates, in turn, are found to have dissociative energy barriers of 10-31 kJ mol-1, depending on leaving group, and are unlikely to undergo pseudorotation prior to dissociation. MP5/6-31G**//MP2/6-31G** calculations indicate that permutational isomerism of phosphoranyl radical is likely to involve barriers of 145 and 127 kJ mol-1 for mechanisms involving transition states of D4h and C4v symmetry respectively.

Facile formation of azines from reactions of singlet methylene and dimethylcarbene with precursor diazirines: theoretical explorations

1999 ◽  
Vol 77 (5-6) ◽  
pp. 540-549 ◽  
Author(s):  
Gennady V Shustov ◽  
Michael TH Liu ◽  
K N Houk
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Ring Opening ◽  
Density Functional ◽  
Activation Barrier ◽  
Thermal Reaction ◽  
Orbital Theory ◽  
Functional Theory ◽  
Activation Barriers ◽  
Singlet Methylene

The reactions of the singlet methylene (1a) and dimethylcarbene (1b), with their diazirine precursors, diazirine (2a), and dimethyldiazirine (2b), have been studied theoretically using ab initio and density functional theory. The reaction has no activation barriers for the parent system (1a + 2a) and proceeds via a reactive complex and a transition state with a small negative enthalpy of activation Δ Hnot =298 = -1.1 kcal mol-1, ΔSnot =298 = -34.4 cal mol-1 K-1, ΔG°298 = 9.2 kcal mol-1) for the dimethyl derivatives (1b + 2b). The formation of N-methylene diazirinium ylides (3a,b) is exothermic by 64-80 kcal mol-1. The isomer, 1,3-diazabicyclo[1.1.0]butane (4a), is more stable (5-12 kcal mol-1) than isomer 3a, but can neither be formed by direct thermal reaction of 1a with 2a nor undergo the direct rearrangement into formaldazine (5a). The rearrangement of ylides 3a,b into azines 5a,b proceeds by conrotatory C3-N1 ring opening. The predicted activation barrier of ca. 15 kcal mol-1 for the ring opening in ylide 3b is in excellent agreement with experimental data. The formation of pyridinium ylides from carbenes and pyridine is also studied.Key words: diazirinium ylide, ab initio MO (molecular orbital) theory, density functional theory, pyridinium ylide, CIS (singles configuration interaction) transition energies.

Reactions of free radicals with aromatic compounds in the gaseous phase. II. Kinetics of the reaction of methyl radicals with phenol

1965 ◽  
Vol 18 (1) ◽  
pp. 20 ◽  
Author(s):  
MFR Mulcahy ◽  
DJ Williams
Keyword(s):  
Free Radicals ◽  
Gaseous Phase ◽  
Hydrogen Abstraction ◽  
High Reactivity ◽  
Phenoxy Radical ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Kinetics Of Formation ◽  
Phenolic Substances ◽  
Kinetics Of

Knowledge of the reactivity of phenols towards simple free radicals is needed to throw light on the behaviour of the phenolic substances involved in the pyrolysis of coal and other organic materials. In the present investigation the reaction between methyl radicals and phenol vapour has been studied a t total pressures from 0.5 to 3 cmHg and temperatures from 445 to 547°K, the concentrations of methyl radicals and phenol being varied from 2 × 10-12 to 4 × 10-11 and 1 × 10-8 to 8 × 10-7 mole cm-3 respectively. The main products identified by gas chromatography were methane and o- and p-cresol, together with a little anisole and 2,4- and 2,6-dimethylphenol. The cresols are produced via hydrogen abstraction Diagram followed by combination of a methyl radical at a ring position of the phenoxy radical either ortho or para to the oxygen atom, e.g. in the case of the para position: Diagram The kinetics can be explained by postulating (a) that the keto forms of the cresols (methylcyclohexadienones) formed initially by reaction (6) have a finite lifetime in the gaseous phase and (b) that these molecules, which contain a tertiary hydrogen atom α to a system of a carbonyl bond and two carbon-carbon double bonds, partly undergo hydrogen abstraction by methyl radicals before they are able to enolize: CH3· + (HCH3 = C6H4 = O → CH4 + CH3C6H4O· The mechanism is consistent with the kinetics of formation of methane, the distribu- tion of the free electron in the phenoxy radical, the formation of o- and p-cresols as major products, the kinetics of formation of the cresols, and the high reactivity of the intermediate product towards methyl radicals.

scholarly journals EFFECT OF SCANDIUM ON HIDROGEN DISSOCIATION ENERGY AT MAGNESIUM SURFACE: AB INITIO DFT STUDY

2010 ◽  
Vol 10 (2) ◽  
pp. 184-188 ◽  
Author(s):  
I Wayan Sutapa ◽  
Ria Armunanto ◽  
Karna Wijaya
Keyword(s):  
Ab Initio ◽  
Dissociation Energy ◽  
Density Functional ◽  
Dissociative Chemisorption ◽  
Functional Theory ◽  
Metal State ◽  
Magnesium Surface ◽  
Kinetics Of ◽  
Good Agreement ◽  
Ab Initio Dft

The dissociative chemisorption of hydrogen on both pure and Sc-incorporated Mg(0001) surfaces have been studied by ab initio density functional theory (DFT) calculation. The calculated dissociation energy of hydrogen molecule on a pure Mg(0001) surface (1.200 eV) is in good agreement with comparable theoretical studies. For the Sc-incorporated Mg(0001) surface, the activated barrier decreases to 0.780 eV due to the strong interaction between the molecular orbital of hydrogen and the d metal state of Sc. This could explain the experimentally observed improvement in absorption kinetics of hydrogen when transition metals have been introduced into the magnesium materials.   Keywords: Dissociation, Adsorption, Chemisorptions, DFT, Magnesium

Exploring the deep interior of ice giants with shock-compression experiments and ab initio simulations: The case of metallic ammonia 

2021 ◽  
Author(s):  
Mandy Bethkenhagen ◽  
Jean-Alexis Hernandez ◽  
Alessandra Benuzzi-Mounaix ◽  
Frederic Datchi ◽  
Martin French ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Equation Of State ◽  
Ab Initio ◽  
Density Functional ◽  
Md Simulations ◽  
Physical Review ◽  
Gradual Transition ◽  
Chemical Physics ◽  
Ab Initio Simulations ◽  
Plasma State

&lt;p&gt;Ammonia is predicted to be one of the major components in the depths of the ice giant planets Uranus and Neptune. Their dynamics, evolution, and interior structure are insufficiently understood and models rely imperatively on data for equation of state and transport properties [1,2]. Despite its great significance, the experimentally accessed region of the ammonia phase diagram today is still very limited in pressure and temperature [3, 4].&lt;/p&gt;&lt;p&gt;We investigate the equation of state, the optical properties and the electrical conductivity of warm dense ammonia by combining laser-driven shock experiments and state-of-the-art density functional theory molecular dynamics (DFT-MD) simulations [5]. The equation of state is probed along the Hugoniot of liquid NH&lt;sub&gt;3 &lt;/sub&gt;up to 350 GPa and 40000 K and in very good agreement with earlier DFT-MD results [6]. Our temperature measurements show a subtle slope change at 7000 K and 90 GPa, which coincides with the gradual transition from a liquid dominated by molecules to a plasma state in our new ab initio simulations. The reflectivity data furnish the first experimental evidence of electronic conduction in high pressure ammonia and are in excellent agreement with the reflectivity computed from atomistic simulations. Corresponding electrical conductivity values are found up to one order of magnitude higher than in water in the 100 GPa regime, with possible implications on the generation of magnetic dynamos in large icy planets&amp;#8217; interiors.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;[1] Scheibe, Nettelmann, Redmer, Astronomy &amp; Astrophysics &lt;strong&gt;632&lt;/strong&gt;, A70 (2019).&lt;/p&gt;&lt;p&gt;[2] Vazan &amp; Helled, Astronomy &amp; Astrophysics &lt;strong&gt;633&lt;/strong&gt;, A50 (2020).&lt;/p&gt;&lt;p&gt;[3] Nellis, Hamilton, Holmes, Radousky, Ree, Mitchell, Nicol, Science &lt;strong&gt;240&lt;/strong&gt;, 779 (1988).&lt;/p&gt;&lt;p&gt;[4] Radousky, Mitchell, Nellis, Journal of Chemical Physics &lt;strong&gt;93&lt;/strong&gt;, 8235 (1990).&lt;/p&gt;&lt;p&gt;[5] Ravasio, Bethkenhagen, Hernandez, Benuzzi-Mounaix, Datchi, French, Guarguaglini, Lefevre, Ninet, Redmer, Vinci, Physical Review Letters &lt;strong&gt;126&lt;/strong&gt;, 025003 (2021).&lt;/p&gt;&lt;p&gt;[6] Bethkenhagen, French, Redmer, Journal of Chemical Physics &lt;strong&gt;138&lt;/strong&gt;, 234504 (2013).&lt;/p&gt;

On the accuracy of density functional theory for ion–molecule clusters. A case study of PLn+ clusters of the first and second row hydrides

1996 ◽  
Vol 74 (6) ◽  
pp. 1032-1048 ◽  
Author(s):  
Xabier Lopez ◽  
Jesus M. Ugalde ◽  
Cecilia Sarasola ◽  
Fernando P. Cossio
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Density Functional ◽  
Second Order ◽  
Bond Critical Point ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Dissociation Energies ◽  
Gradient Corrections ◽  
Moller Plesset

PLn+ clusters (n = 1, 2 and L = NH3, OH2, FH, PH3, SH2, CIH) in both their triplet and singlet states have been characterized by common approximate density functional methods, SVWN, BVWN, BLYP, and B3LYP. The phosphorus–ligand distances (R), dissociation energies (D0), triplet–singlet gaps (Δt−s), and several bond properties, such as the electron density (ρ(rc)), the Laplacian [Formula: see text] and the local energy density H(rc) at the bond critical point, were compared with those obtained by accurate ab initio molecular orbital theory, namely, second-order Møller–Plesset (MP2) and G2 theory. In general, it is observed that the local spin density approximation (SVWN) yields stronger bonds than ab initio molecular orbital theory. However, addition of gradient corrections to the exchange functional (BVWN) yields ion–molecule bonds that are too weak. Finally, taking account also of gradient corrections to the correlation functional (BLYP) leads to very close agreement with ab initio results. Among these functional, Becke's hybrid functional, B3LYP, best fit the second-order Møller–Plesset and G2 data, reproducing the qualitative trends observed for the above-mentioned properties of phosphorus clusters, except for [Formula: see text] This fit is particularly good for distances, dissociation energies, and electron densities at the bond critical point, and both methods show similar deviations of the values of binding energies and triplet–singlet gap with respect to the G2 data. Compared with our most accurate ab initio molecular orbital data, namely G2, significant overbinding for the singlets, larger for one-ligand than for two-ligand complexes, and significant overestimation of the triplet–singlet gap for one-ligand complexes is observed for both methods, namely, B3LYP and MP2. The deviations at the second-order Møller–Plesset level of theory are mainly due to the lack of quadratic configuration interaction (QCI) corrections, and this deficiency is also present to some extent in B3LYP. However, for larger clusters these corrections are smaller, therefore the B3LYP functional is expected to lead to accurate descriptions. Key words: DFT, Bader analysis, G2, ion–molecule complexes, phosphorus.

Sign in / Sign up

Export Citation Format

Share Document