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Volumn 1, Issue , 2007, Pages 303-348

Theoretical Aspects of Proton Transfer Reactions in a Polar Environment

Author keywords

Adiabatic proton transfer; Hydrogen transfer reactions; Nonadiabatic 'tunneling' proton transfer; Polar environments; Theoretical aspects

Indexed keywords


EID: 34548227922     PISSN: None     EISSN: None     Source Type: Book    
DOI: 10.1002/9783527611546.ch10     Document Type: Chapter
Times cited : (14)

References (168)
  • 19
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    • 2nd edn. Cornell University Press, Ithaca, NY
    • Bell, R. P. The Proton in Chemistry. 2nd edn. Cornell University Press, Ithaca, NY 1973;
    • (1973) The Proton in Chemistry
    • Bell, R.P.1
  • 40
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    • Isotope Effects on Enzyme-Catalyzed Reactions
    • in, Cleland, W. W.; O'Leary, M. H.; Northrop, D. B. (Eds.), University Park Press, Baltimore, MD
    • Kresge, A. J., in Isotope Effects on Enzyme-Catalyzed Reactions, Cleland, W. W.; O'Leary, M. H.; Northrop, D. B. (Eds.), University Park Press, Baltimore, MD 1977, pp. 37-63.
    • (1977) , pp. 37-63
    • Kresge, A.J.1
  • 46
    • 0013439382 scopus 로고
    • Proton Transfer Reactions
    • in, Caldin, E.; Gold, V. (Eds.), Chapman and Hall, London
    • More O'Ferral, R. A. in Proton Transfer Reactions, Caldin, E.; Gold, V. (Eds.), Chapman and Hall, London 1975, pp. 201-261.
    • (1975) , pp. 201-261
    • More O'Ferral, R.A.1
  • 49
    • 84891282254 scopus 로고    scopus 로고
    • A KIE expression of the form in Eq. (10.2) neglects any mass dependence in the prefactor, the contribution of which is usually negligible, except in the case of tunneling [8, 11, 17], as well as assumes that the proton primarily resides in it ground (stretching and bending)vibrational state.
    • A KIE expression of the form in Eq. (10.2) neglects any mass dependence in the prefactor, the contribution of which is usually negligible, except in the case of tunneling [8, 11, 17], as well as assumes that the proton primarily resides in it ground (stretching and bending)vibrational state.
  • 61
    • 84891303568 scopus 로고    scopus 로고
    • Calculations of KIEs derived from a classical reaction path (e.g. the MEP) in the presence of a solvent or polar environment typically add quantum corrections to that path [22]. Such a reaction path, however, includes classical motion of the proton, especially near the TS, and thus this technique exhibits no difference in quantum corrections between H and D at the TS for a symmetric reaction (DGrxn=0) [22b], in contrast to the present picture. In variational TS theory for gas phase H atom transfer, the TS significantly deviates from the MEP TS and is isotope-dependent [23]. This feature has been calculated for PT in an enzyme, where the KIE has been diminished because the TS position significantly differs between H and D even in a symmetric case [22e].
    • Calculations of KIEs derived from a classical reaction path (e.g. the MEP) in the presence of a solvent or polar environment typically add quantum corrections to that path [22]. Such a reaction path, however, includes classical motion of the proton, especially near the TS, and thus this technique exhibits no difference in quantum corrections between H and D at the TS for a symmetric reaction (DGrxn=0) [22b], in contrast to the present picture. In variational TS theory for gas phase H atom transfer, the TS significantly deviates from the MEP TS and is isotope-dependent [23]. This feature has been calculated for PT in an enzyme, where the KIE has been diminished because the TS position significantly differs between H and D even in a symmetric case [22e].
  • 70
    • 0025743628 scopus 로고
    • For examples of the equilibrium solvation picture for PT in a complex system, see
    • For examples of the equilibrium solvation picture for PT in a complex system, see Bash, P. A.; Field, M. J.; Davenport, R. C.; Petsko, G. A.; Ringe, D.; Karplus, M. Biochemistry 1991, 30, 5826-5832;
    • (1991) Biochemistry , vol.30 , pp. 5826-5832
    • Bash, P.A.1    Field, M.J.2    Davenport, R.C.3    Petsko, G.A.4    Ringe, D.5    Karplus, M.6
  • 88
    • 84891335588 scopus 로고    scopus 로고
    • While these two regimes are distinctly separated, there may exist real systems where different isotopes will be in different regimes. For example, the proton potential barrier at the solvent TS configuration may be small enough such that the proton ground vibration state may be above the barrier, but still large enough such that the deuteron ground vibration state, with a smaller ZPE, may be below the barrier. The present discussion assumes that all isotopes transfer in the same regime.
    • While these two regimes are distinctly separated, there may exist real systems where different isotopes will be in different regimes. For example, the proton potential barrier at the solvent TS configuration may be small enough such that the proton ground vibration state may be above the barrier, but still large enough such that the deuteron ground vibration state, with a smaller ZPE, may be below the barrier. The present discussion assumes that all isotopes transfer in the same regime.
  • 107
    • 0000044605 scopus 로고    scopus 로고
    • The recrossing correction was calculated for both ground and excited H-bond vibrational states at the transition state in Ref. [2d]. The reaction is in the adiabatic PT limit, as opposed to an earlier, more approximate treatment (Azzouz, H.; Borgis, D. J. Chem. Phys. 1993, 98, 7361-7374;
    • The recrossing correction was calculated for both ground and excited H-bond vibrational states at the transition state in Ref. [2d]. The reaction is in the adiabatic PT limit, as opposed to an earlier, more approximate treatment (Azzouz, H.; Borgis, D. J. Chem. Phys. 1993, 98, 7361-7374;
  • 108
    • 0028477466 scopus 로고
    • an important feature to emphasize here since this earlier treatment of the reaction has been subsequently widely used as a reference model for various calculation methods.
    • Azzouz, H.; Borgis, D. J. Mol. Liq. 1994, 61, 17-36), an important feature to emphasize here since this earlier treatment of the reaction has been subsequently widely used as a reference model for various calculation methods.
    • (1994) J. Mol. Liq , vol.61 , pp. 17-36
    • Azzouz, H.1    Borgis, D.2
  • 126
    • 84891335892 scopus 로고    scopus 로고
    • For a perspective on this, we refer the reader to (b). In this connection, see also (c) and (d) concerning the issue of a hydronium ion in the neighborhood of anion produced by PT.
    • For a perspective on this, we refer the reader to (b). In this connection, see also (c) and (d) concerning the issue of a hydronium ion in the neighborhood of anion produced by PT.
  • 127
    • 0038788620 scopus 로고    scopus 로고
    • Ultrafast Hydrogen Bonding Dynamics and Proton Transfer Processes in the Condensed Phase
    • in, Elsaesser, T.; Bakker, H.J. (Eds.), Kluwer Academic, Amsterdam
    • Pines, E.; Pines D. in Ultrafast Hydrogen Bonding Dynamics and Proton Transfer Processes in the Condensed Phase, Elsaesser, T.; Bakker, H.J. (Eds.), Kluwer Academic, Amsterdam, 2002, 155-184;
    • (2002) , pp. 155-184
    • Pines, E.1    Pines, D.2
  • 130
    • 84891291573 scopus 로고    scopus 로고
    • N is defined throughout as the free energy difference between reactant and product H-bond complexes, a free energy difference that is rarely experimentally determined. The full connection to experimentally determined quantities is discussed in Ref. 43 of Ref. [4].
    • N is defined throughout as the free energy difference between reactant and product H-bond complexes, a free energy difference that is rarely experimentally determined. The full connection to experimentally determined quantities is discussed in Ref. 43 of Ref. [4].
  • 132
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    • The Evans-Polanyi relations were developed mainly for gas phase reactions but are also useful in solution in the context of the standard picture.
    • Evans, M. G.; Polanyi, M. Trans. Faraday Soc. 1938, 34, 11-24. The Evans-Polanyi relations were developed mainly for gas phase reactions but are also useful in solution in the context of the standard picture.
    • (1938) Trans. Faraday Soc , vol.34 , pp. 11-24
    • Evans, M.G.1    Polanyi, M.2
  • 135
    • 84891332020 scopus 로고    scopus 로고
    • 0 is not expected to be exactly 0.5 due to 'intrinsic' asymmetry, but the deviation from 0.5 for either H or D is not expected to be significant. For further discussion, see Ref. 45 of Ref. [4].
    • 0 is not expected to be exactly 0.5 due to 'intrinsic' asymmetry, but the deviation from 0.5 for either H or D is not expected to be significant. For further discussion, see Ref. 45 of Ref. [4].
  • 139
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    • Isotope Effects In Chemistry and Biology
    • in, Kohen, A.; Limbach, H.-H. (Eds.), Taylor & Francis, Boca Raton FL, Ch. 7
    • Limbach, H.-H.; Denisov, G. S.; Golubev, N. S. in Isotope Effects In Chemistry and Biology, Kohen, A.; Limbach, H.-H. (Eds.), Taylor & Francis, Boca Raton FL, 2005, Ch. 7, pp. 193-230.
    • (2005) , pp. 193-230
    • Limbach, H.-H.1    Denisov, G.S.2    Golubev, N.S.3
  • 147
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    • S is analogous to the electronic diabatic solvent reorganization energy. Even though the reorganization energies and couplings are analogous, the physical picture behind the two reaction types is quite different. The reorganization energy for proton tunneling is the free energy difference associated with a Franck-Condon-like excitation (all nuclear and solvent modes other than the proton mode are held fixed) of the ground diabatic proton vibrational state at the equilibrium reactant solvent position to the ground product diabatic proton vibrational state, followed by relaxation along the solvent coordinate to the equilibrium solvent product position (See Fig. 10.13(d)).
    • S is analogous to the electronic diabatic solvent reorganization energy. Even though the reorganization energies and couplings are analogous, the physical picture behind the two reaction types is quite different. The reorganization energy for proton tunneling is the free energy difference associated with a Franck-Condon-like excitation (all nuclear and solvent modes other than the proton mode are held fixed) of the ground diabatic proton vibrational state at the equilibrium reactant solvent position to the ground product diabatic proton vibrational state, followed by relaxation along the solvent coordinate to the equilibrium solvent product position (See Fig. 10.13(d)).
  • 148
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    • Discussion of the influence of bending on these results can be found in Refs. [4] and [5a]
    • Discussion of the influence of bending on these results can be found in Refs. [4] and [5a].
  • 149
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    • The H-bond vibrational mode is assumed to remain significantly unchanged while the reaction coordinate fluctuates from the 0-0 TS to either the 0-1 or 1-0 TS.
    • The H-bond vibrational mode is assumed to remain significantly unchanged while the reaction coordinate fluctuates from the 0-0 TS to either the 0-1 or 1-0 TS.
  • 150
    • 84891305993 scopus 로고    scopus 로고
    • This is particularly true for H atom transfer reactions because they are weakly coupled to a polar environment, i.e. small reorganization energies (cf. H atom transfer reaction in Ref. [1e]).
    • This is particularly true for H atom transfer reactions because they are weakly coupled to a polar environment, i.e. small reorganization energies (cf. H atom transfer reaction in Ref. [1e]).
  • 151
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    • o are obtained.
    • o are obtained.
  • 152
    • 84891304156 scopus 로고    scopus 로고
    • N and decreased Eg [5].
    • N and decreased Eg [5].
  • 156
    • 84891324372 scopus 로고    scopus 로고
    • Further remarks on the T dependence of the Swain-Schaad ratio can be found in Section 3c of Ref. [5].
    • Further remarks on the T dependence of the Swain-Schaad ratio can be found in Section 3c of Ref. [5].
  • 157
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    • Isotope Effects in Chemistry and Biology
    • in, Kohen, A.; Limbach, H.-H. (Eds.), Marcel Decker, Inc., New York, Ch.16
    • E. Pines, in Isotope Effects in Chemistry and Biology, Kohen, A.; Limbach, H.-H. (Eds.), Marcel Decker, Inc., New York, 2005, Ch.16, pp. 451-464.
    • (2005) , pp. 451-464
    • Pines, E.1
  • 158
    • 84891286849 scopus 로고    scopus 로고
    • The observed KIEs [9c, 9e, 63] were measured by changing the solvent from H2O to D2O, and while this change in solvent introduces other possible solvent isotope effects (i.e. viscosity), the rate limiting step in each case has been shown to be a PT step (or a series of PT steps), and thus the measured KIE corresponds to P.
    • The observed KIEs [9c, 9e, 63] were measured by changing the solvent from H2O to D2O, and while this change in solvent introduces other possible solvent isotope effects (i.e. viscosity), the rate limiting step in each case has been shown to be a PT step (or a series of PT steps), and thus the measured KIE corresponds to P.
  • 159
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    • Ultrafast Reaction Dynamics at Atomic-Scale Resolution Femtochemistry and Femtobiology
    • in, Nobel Symposium 101, Villy Sundstrom (Ed.), Imperial College Press, London
    • Kim, H. J.; Staib, A.; Hynes, J. T. in Ultrafast Reaction Dynamics at Atomic-Scale Resolution Femtochemistry and Femtobiology, Nobel Symposium 101, Villy Sundstrom (Ed.), Imperial College Press, London, 1998, pp. 510-527.
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    • Ultrafast Hydrogen Bonding Dynamics and Proton Transfer Processes in the Condensed Phase
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    • Elsaesser, T. in Ultrafast Hydrogen Bonding Dynamics and Proton Transfer Processes in the Condensed Phase, Elsaesser, T.; Bakker, H.J. (Eds.), Kluwer Academic, Amsterdam, 2002, pp. 119-153.
    • (2002) , pp. 119-153
    • Elsaesser, T.1


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