The main feature of these redox reactions is that, unlike most reactions, they have steric factors greater than unity; that is, they take place faster than predicted by collision theory. This is explained by the fact that the colliding particles have greater cross sections than the pure geometrical ones calculated from their radii, because when the particles are close enough, an electron "jumps" (therefore the name) from one of the particles to the other one, forming an anion and a cation which subsequently attract each other. Harpoon reactions usually take place in the gas phase, but they are also possible in condensed media.[4][5]
The predicted rate constant can be improved by using a better estimation of the steric factor. A rough approximation is that the largest separation Rx at which charge transfer can take place on energetic grounds, can be estimated from the solution of the following equation that determines the largest distance at which the Coulombic attraction between the two oppositely charged ions is sufficient to provide the energy ΔE0
^Polanyi, M. (1920-01-01). "Zum Ursprung der chemischen Energie". Zeitschrift für Physik (in German). 3 (1): 31–35. doi:10.1007/BF01356227. ISSN 0044-3328. S2CID 120940201.
^Herschbach, D. R. (2007-03-14), "Reactive Scattering in Molecular Beams", in Ross, John (ed.), Advances in Chemical Physics, Advances in Chemical Physics, Hoboken, NJ, USA: John Wiley & Sons, Inc., pp. 319–393, doi:10.1002/9780470143568.ch9, ISBN978-0-470-14356-8, retrieved 2022-04-13
^Fajardo, Mario E.; V. A. Apkarian (November 15, 1986). "Cooperative photoabsorption induced charge transfer reaction dynamics in rare gas solids. I. Photodynamics of localized xenon chloride exciplexes". The Journal of Chemical Physics. 85 (10): 5660–5681. Bibcode:1986JChPh..85.5660F. doi:10.1063/1.451579.
^Fajardo, Mario E.; V. A. Apkarian (October 1, 1988). "Charge transfer photodynamics in halogen doped xenon matrices. II. Photoinduced harpooning and the delocalized charge transfer states of solid xenon halides (F, Cl, Br, I)". The Journal of Chemical Physics. 89 (7): 4102–4123. Bibcode:1988JChPh..89.4102F. doi:10.1063/1.454846.
^Atkins, Peter (2014). Atkins' Physical Chemistry. Oxford. p. 875. ISBN9780199697403.
^Okada, F.; L. Wiedeman; V. A. Apkarian (February 23, 1989). "Photoinduced harpoon reactions as a probe of condensed-phase dynamics: iodine chloride in liquid and solid xenon". Journal of Physical Chemistry. 93 (4): 1267–1272. doi:10.1021/j100341a020.
^Skowronek, S.; J. B. Jiméne; A. González Ureña (8 July 1999). "Resonances in the Ba...FCH3 + hν → BaF + CH3 reaction probability". Journal of Chemical Physics. 111 (4): 460–463. Bibcode:1999JChPh.111..460S. doi:10.1063/1.479326.
^Wiskerke, A. E.; S. Stolte; H. J. Loesch; R. D. Levine (2000). "K + CH3I → KI + CH3 revisited: the total reaction cross section and its energy and orientation dependence. A case study of an intermolecular electron transfer". Physical Chemistry Chemical Physics. 2 (4): 757–767. Bibcode:2000PCCP....2..757W. doi:10.1039/a907701d.
August 16, 2023
harpoon, reaction, harpoon, reaction, type, chemical, reaction, first, proposed, michael, polanyi, 1920, whose, mechanism, also, called, harpooning, mechanism, involves, neutral, reactants, undergoing, electron, transfer, over, relatively, long, distance, form. A harpoon reaction is a type of chemical reaction first proposed by Michael Polanyi in 1920 1 2 whose mechanism also called the harpooning mechanism involves two neutral reactants undergoing an electron transfer over a relatively long distance to form ions that then attract each other closer together 3 For example a metal atom and a halogen might react to form a cation and anion respectively leading to a combined metal halide The main feature of these redox reactions is that unlike most reactions they have steric factors greater than unity that is they take place faster than predicted by collision theory This is explained by the fact that the colliding particles have greater cross sections than the pure geometrical ones calculated from their radii because when the particles are close enough an electron jumps therefore the name from one of the particles to the other one forming an anion and a cation which subsequently attract each other Harpoon reactions usually take place in the gas phase but they are also possible in condensed media 4 5 The predicted rate constant can be improved by using a better estimation of the steric factor A rough approximation is that the largest separation Rx at which charge transfer can take place on energetic grounds can be estimated from the solution of the following equation that determines the largest distance at which the Coulombic attraction between the two oppositely charged ions is sufficient to provide the energy DE0 q e 2 R x D E 0 0 displaystyle frac q e 2 R x Delta E 0 0 6 With D E 0 E i E e a displaystyle Delta E 0 E i E e a where Ei is the ionization potential of the metal and Eea is the electron affinity of the halogen Examples of harpoon reactions EditGenerically Rg X2 hn RgX X 7 where Rg is a rare gas and X is a halogen Ba FCH3 hn BaF CH3 8 K CH3I KI CH3 9 References Edit Polanyi M 1920 01 01 Zum Ursprung der chemischen Energie Zeitschrift fur Physik in German 3 1 31 35 doi 10 1007 BF01356227 ISSN 0044 3328 S2CID 120940201 Herschbach D R 2007 03 14 Reactive Scattering in Molecular Beams in Ross John ed Advances in Chemical Physics Advances in Chemical Physics Hoboken NJ USA John Wiley amp Sons Inc pp 319 393 doi 10 1002 9780470143568 ch9 ISBN 978 0 470 14356 8 retrieved 2022 04 13 IUPAC Compendium of Chemical Terminology 2nd ed the Gold Book 1997 Online corrected version 2006 harpoon mechanism doi 10 1351 goldbook H02746 Fajardo Mario E V A Apkarian November 15 1986 Cooperative photoabsorption induced charge transfer reaction dynamics in rare gas solids I Photodynamics of localized xenon chloride exciplexes The Journal of Chemical Physics 85 10 5660 5681 Bibcode 1986JChPh 85 5660F doi 10 1063 1 451579 Fajardo Mario E V A Apkarian October 1 1988 Charge transfer photodynamics in halogen doped xenon matrices II Photoinduced harpooning and the delocalized charge transfer states of solid xenon halides F Cl Br I The Journal of Chemical Physics 89 7 4102 4123 Bibcode 1988JChPh 89 4102F doi 10 1063 1 454846 Atkins Peter 2014 Atkins Physical Chemistry Oxford p 875 ISBN 9780199697403 Okada F L Wiedeman V A Apkarian February 23 1989 Photoinduced harpoon reactions as a probe of condensed phase dynamics iodine chloride in liquid and solid xenon Journal of Physical Chemistry 93 4 1267 1272 doi 10 1021 j100341a020 Skowronek S J B Jimene A Gonzalez Urena 8 July 1999 Resonances in the Ba FCH3 hn BaF CH3 reaction probability Journal of Chemical Physics 111 4 460 463 Bibcode 1999JChPh 111 460S doi 10 1063 1 479326 Wiskerke A E S Stolte H J Loesch R D Levine 2000 K CH3I KI CH3 revisited the total reaction cross section and its energy and orientation dependence A case study of an intermolecular electron transfer Physical Chemistry Chemical Physics 2 4 757 767 Bibcode 2000PCCP 2 757W doi 10 1039 a907701d Retrieved from https en wikipedia org w index php title Harpoon reaction amp oldid 1138999019, wikipedia, wiki, book, books, library,
