HOMO- AND HETEROLYTIC MECHANISMS IN THE REACTIONS OF NORMAL ALKANES IN THE PRESENCE OF PALLADIUM (II)
DOI:
https://doi.org/10.32782/naturaljournal.11.2025.37Keywords:
alkanes, palladium (II), OH• radical, mechanism, correlation analysis, PM7 methodAbstract
Normal alkanes (n-AlkH) are used mainly as non-renewable fossil fuels due to their inertness, which prevents chemical conversion into high value-added products. The path to such products is oxidative functionalization along the saturated C–H bond, so its mechanisms become the subject of numerous studies. Functionalization of the most inert of methane alkanes CH4, the main constituent of natural gas and oil, under mild conditions of – t up to 200 °C and normal pressure, remains a challenge for chemists today, a commercially viable selective functionalization technology is not an achievable goal.This work is devoted to the study and comparison of the mechanisms of n-AlkH reactions from CH4 to decane C10H22, series C1–C10, in the gas phase with the hydroxyl radical OH•, and from ethane C2H6 to C10H22, C2–C10, in palladium (II) sulfuric acid solutions through correlation analysis, in which kinetic data are compared with the ionization potentials of alkanes and the bond energy C–H and quantum-chemical calculated thermochemistry of possible limiting reactions.In contrast to the reaction of alkanes with OH•, for which a homolytic abstraction of the H atom from C–H occurs in the entire C1–C10 series, in the solution of Pd2+ – 94.9% H2SO4 at 90 °C, the transformationsof C2–C10 turned out to be different in mechanisms for C2H6 and the rest from propane C3H8 to C10H22. For C3–C10 the reaction begins with the abstraction of an electron from AlkH by the PdHSO4+ complex, continues with the transfer of the proton H+ from the cation n-AlkH+ to the HSO4– bisulfate anion, followed by the abstraction of the electron from the formed alkyl radical Alk• and the appearanceof the alkyl carbocation Alk+. The ethyl carbocation C2H5+ is formed by another mechanism, which begins with the abstraction of the H atom from ethane by palladium (II) and continues with the subsequent abstraction of the Pd2+ electron ion from the formed C2H5• radical.The enthalpy values of the hexane C6H14 reactions calculated by the semi-empirical PM7 method ina system with Pd2+ indicate the highest thermochemical profitability of three abstraction reactions: electron, proton, electron, proposed for C3–C10.
References
Волкова Л., Опейда Й. Аналіз механізму реакцій н-алканів у сірчанокислих розчинах паладію (II). Поступ в нафтогазопереробній та нафтохімічній промисловості – 2024. Львів, 2024. С. 61–65.
Волкова Л.К., Опейда Й.О., Аніщенко В.М. Утворення подвійних зв’язків у дегідрогенізації циклогексану. Хімічні проблеми сьогодення. Вінниця, 2024. С. 107.
Волкова Л., Опейда Л., Пастернак О. Механізми окиcної функціоналізації зв’язків С–Н н-алканів у сірчанокислих розчинах паладію (II). Поступ в нафтогазопереробній та нафтохімічній промисловості – 2022. Львів, 2022. С. 49–52.
Волкова Л.К., Опейда Й.О. Активація зв’язків C–H нормальних алканів у сірчанокислих розчинах Mn(III) / Mn(II). Каталіз та нафтохімія. 2021. № 32. С. 75–85. https://doi.org/10.15407/kataliz2021.32.075.
Alkane Functionalization. / Editor by A.J.L. Pombeiro and M.F.C. Guedes da Silva. John Wiley & Sons Ltd, 2019. 683 p. ISBN: 9781119378808. DOI: 10.1002/9781119379256.
Anslyn E.V., Dougherty D.A. Modern physical organic chemistry. University science books. University Science Books Sausalito, California. 2006. 1095 p. [Electronic resource]. URL: https://uscibooks.aip.org/books/modern-physical-organic-chemistry/ (access date 27.12.2024).
Atkinson R. Kinetics of the gas-phase reactions of OH radicals with alkanes and cycloalkanes. Atmospheric Chemistry and Physics. 2003. Vol. 3. P. 2233–2307. https://doi.org/10.5194/acp-3-2233-2003.
Chempath S., Bell A.T. Density Functional Theory Analysis of the Reaction Pathway for Methane Oxidation to Acetic Acid Catalyzed by Pd2+ in Sulfuric Acid. Journal of the American Chemical Society. 2006. Vol. 128. No. 14. P. 4650–4657. https://doi.org/10.1021/ja055756i.
Comprehensive Handbook of Chemical Bond Energies. Edited by Yu-Ran Luo. Taylor and Francis Group, LLC. 2007. 1688 p. https://doi.org/10.1201/9781420007282.
Crabtree R.H. Aspects of methane chemistry. Chemical Reviews. 1995. Vol. 95. No. 4. P. 987–1007. https://pubs.acs.org/doi/10.1021/cr00036a005.
Crabtree R.H. Introduction to Selective Functionalization of C–H Bonds. Chemical Reviews. 2010. Vol. 110. P. 575. https://pubs.acs.org/doi/10.1021/cr900388d.
Dalton T., Faber T., Glorius F. C–H activation: toward sustainability and applications. ACS Central Science. 2021. Vol. 7. No. 2. P. 245–261. https://doi.org/10.1021/acscentsci.0c01413.
Goldberg K.I., Goldman A.S. Large-Scale Selective Functionalization of Alkanes. Accounts of Chemical Research. 2017. Vol. 50. P. 620−626. https://pubs.acs.org/doi/10.1021/acs. accounts.6b00621.
Gunsalus N.J., Koppaka A., Park S.H., Bischof S.M., Hashiguchi B.G., Periana R.A. Homogeneous Functionalization of Methane. Chemical Reviews. 2017. Vol. 117. No. 13. Р. 8521–8573. https://pubs.acs.org/doi/10.1021/acs.chemrev.6b00739.
Gunsalus N.J., Koppaka A., Hashiguchi B.G., Konnick M.M., Park S.H., Ess D.H., Periana R.A. SN2 and E2 Branching of Main-Group-Metal Alkyl Intermediates in Alkane CH Oxidation: Mechanistic Investigation Using Isotopically Labeled Main-Group-Metal Alkyls. Organometallics. 2020. Vol. 39. No. 10. P. 1907–1916. https://doi.org/10.1021/acs.organomet.0c00120.
Hartwig J.F. Evolution of C–H Bond Functionalization from Methane to Methodology. Journal of the American Chemical Society. 2016. Vol. 138. No. 1. P. 2–24. https://doi.org/10.1021/jacs.5b08707.
He J., Wasa M., Chan K.S., Shao Q., Yu J.-Q. Palladium-catalyzed transformations of alkyl C–H bonds. Chemical Reviews. 2017. Vol. 117. No. 13. P. 8754–8786. https://pubs.acs.org/doi/10.1021/acs.chemrev.6b00622.
King C.R., Rollins N., Holdaway A., Konnick M.M., Periana R.A., Ess D.H. Electrophilic Impact of High-Oxidation State Main-Group Metal and Ligands on Alkane C–H Activation and Functionalization Reactions. Organometallics. 2018. Vol. 37. No. 18. Р. 3045–3054. https://pubs. acs.org/doi/10.1021/acs.organomet.8b00418.
King C.R., Holdaway A., Durrant G., Wheeler J., Suaava L., Konnick M.M., Periana R.A., Ess D.H. Supermetal: SbF5-mediated methane oxidation occurs by C–H activation and isobutane oxidation occurs by hydride transfer. Dalton Transactions. 2019. Vol. 48. P. 17029–17036. https://doi.org/10.1039/C9DT03564H.
Konnick M.M., Bischof S.M., Yousufuddin M., Hashiguchi B.G., Ess D.H., Periana R.A. A Mechanistic Change Results in 100 Times Faster CH Functionalization for Ethane versus Methane by a Homogeneous Pt Catalyst. Journal of the American Chemical Society. 2014. Vol. 136. P. 10085−10094. https://pubs.acs.org/doi/10.1021/ja504368r.
Koppaka A., Gunsalus N.J., Periana R.A. “Homogeneous Methane Functionalization” hapter 12, 46 p. in book Hu B., Shekhawat D. Direct Natural Gas Conversion to Value-Added Chemicals. Pub. Location Boca Raton, Imprint CRC Press. 2020. – eBook ISBN 9780429022852.
Krämer T., Gyton M.R., Bustos I., Sinclair M.J.G., Tan Sze-yin, Wedge C.J., Macgregor S.A., Chaplin A.B. Stability and C−H Bond Activation Reactions of Palladium (I) and Platinum (I) Metalloradicals: Carbon-to-Metal H-Atom Transfer and an Organometallic Radical Rebound Mechanism. Journal of the American Chemical Society. 2023. Vol. 145. P. 14087−14100. https://doi.org/10.1021/jacs.3c04167.
Labinger J.A. Alkane Functionalization via Electrophilic Activation. In: Alkane CH Activation by Single-Site Metal Catalysis. Springer, Dordrecht. 2012. Р. 17–71. https://doi.org/10.1007/978-90-481-3698-8_2.
Na H., Wessel A.J., Kim Seoung-Tae, Baik Mu-Hyun, Mirica L.M. Csp3–H Bond Activation Mediated by a Pd (II) Complex under Mild Conditions. Inorganic Chemistry Frontiers. 2024. Vol. 11. P. 4415–4423. https://doi.org/10.1039/D4QI01017E.
NIST Chemistry WEbBook. [Electronic resource]. URL: https://webbook.nist.gov/chemistry/(access date 27.12.2024). https://doi.org/10.18434/T4D303.
Niu K., Chi L., Rosen J., Björk J. C–H activation of light alkanes on MXenes predicted by hydrogen affinity. Physical Chemistry Chemical Physics. 2020. Vol. 33. No. 33. P. 18622–18630. https://doi.org/10.1039/D0CP02471F.
Periana R.A., Bhalla G., Tenn III W.J., Young K.J.H., Liu X.Y., Mironov O., Jones CJ, Ziatdinov V.R. Perspectives on some challenges and approaches for developing the next genera-tion of selective, low temperature, oxidation catalysts for alkane hydroxylation based on the CH activation reaction. Journal of Molecular Catalysis A: Chemical. 2004. Vol. 220. No. 1. P. 7–25. https://doi.org/10.1016/j.molcata.2004.05.036.
Shilov A.E., Shul’pin G.B. Activation of C−H Bonds by Metal Complexes. Chemical Reviews. 1997. Vol. 97. No. 8. P. 2879−2932. https://pubs.acs.org/doi/10.1021/cr9411886.
Stewart J.J.P. Optimization of parameters for semiempirical methods VI: more modifications to the NDDO approximations and re-optimization of parameters. Journal of Molecular Modeling. 2013. Vol. 19. P. 1–32. https://doi.org/10.1007/s00894-012-1667-x.
Stewart J.J.P. MOPAC 2016. Stewart Computational Chemistry. Colorado Springs. USA. 2016. [Electronic resource]. URL: http://openmopac.net/MOPAC2016.html (access date 27.12.2024).
Volkova L.K., Opeida I.A. On the mechanisms of reactions of saturated hydrocarbons in sulfuric acid solutions of manganese(III)/manganese(II) and paladium(II) complexes. P. 313–325. Chemical and biopharmaceutical technologies: сollection of scientific papers / by general ed. V. Bessarabov and V. Lubenets. Tallinn: Nordic Sci Publisher, 2023. 392 p.
Zerella M., Kahros A., Bell A.T. Methane oxidation to acetic acid by Pd2+ cations in the pres-ence of oxygen. Journal of Catalysis. 2006. Vol. 237. P. 111–117. https://doi.org/10.1016/ j.jcat.2005.10.023.
