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Chapter 2 Linear Free Energy Relationship and Kinetic Isotope Effect

Chapter 2 Linear Free Energy Relationship and Kinetic Isotope Effect. Substituent Effects. Field effects Inductive effects Resonance effects Polarizability effects Steric effects Solvation effects. Hammett Plots -- a general method for examining changes in charges during a reaction.

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Chapter 2 Linear Free Energy Relationship and Kinetic Isotope Effect

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  1. Chapter 2 Linear Free Energy Relationship and Kinetic Isotope Effect

  2. Substituent Effects • Field effects • Inductive effects • Resonance effects • Polarizability effects • Steric effects • Solvation effects

  3. Hammett Plots-- a general method for examining changes in charges during a reaction. • Sigma values KX s = log (KX/KH)

  4. Hammett Plots sr = log (KX/KH) sr = log (kX/kH) • Rho values • When r>1< the reaction under study is more sensitive to substitents than benzoic acid, and negative charge is building during the reaction. • When 0<r<1, the reaction is less sensitive to substituents than benzoic acid, but negative charge is still building • When r is equal to or close to 0, the reaction shows no substituent effects. • When r is negative, the reaction is creating positive charge.

  5. P. Jr. Wentworth, A. Datta, S. Smith, A. Marshall, L. J. Partridge, and G. M. Blackburn, J. Am. Chem. Soc., 1997, 119, 2315

  6. J. P. Richard, and W. P. Jencks, J. Am. Chem. Soc., 1982, 104, 4689.

  7. J. Lehman, and G. C. Lloyd-Jones, Tetrahedron, 1995, 8863

  8. Kinetic Isotope Effect • Stretching vibration • Bending vibration n m-1/2 ∞ m: reduced mass

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