Cage effects in the photochemistry of (S)-(+)-2-phenylpropiophenone

“…A similar equation can be derived when the changing reagent is the nucleophile X in reaction (2): (17) In this case a can be approximately measured as Pnuc.…”

Section: A = M + 1 -( Y Y + 6 / a + Y X / A 2 )mentioning

confidence: 98%

“…Equations (15) and (17) also apply to cases where m # n. In this case, for example the Menschutkin reaction, yx most likely is of the opposite sign from yy, and the assumption that they are equal is clearly wrong. a = (yx + 6 / a + y y / a 2 ) -n The Menschutkin reaction has been extensively studied from many aspects; many are quoted by Ando et al, " Arnett and Reich," Matsui and T~k u r a~~ and Abraham34.…”

Section: A = M + 1 -( Y Y + 6 / a + Y X / A 2 )mentioning

confidence: 99%

Rate‐equilibrium LFER characterization of transition states: The interpretation of α

Lewis

1990

J of Physical Organic Chem

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The effect of substituents on the rate of a reaction and the effect of the same substituents on the equilibrium can often be related by a linear free energy relation (LFER): log k− = α log K= + constant, where k+ and K= are the rate constant and the equilibrium constant, respectively. This review, concentrating on group transfers, adds to many studies describing the use of α to describe the transition state. Although the use of α to describe transition states is general, group transfers constitute a simple class allowing a fairly complete description yet illustrating two often neglected contributions. Group transfers can be described by the Marcus equation relating rate to an average identity rate and the equilibrium constant; a major contributor to the slope, α, of the rate‐equilibrium LFER is the variation of identity rates with substituent, rather than reflecting product‐like character. Substituent effect LFERs are predominantly attributable to interaction of charges with the substituent. However, α is not an exact measure of the charge on the substituent‐containing group, because in a transition state, but often not in a reaction product, there are more remote centers of charge which exert a smaller attenuated effect. A simple treatment of this attenuation for group transfers is proposed. The possibility of application of these ideas to proton transfer reactions and the interpretation of the Brønsted α (or β) is proposed.

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“…when Xis a member of the same series k x x can be estimated from various LFERs. This method gives about the same value as the isotopic method for the very slow reaction with thiophenoxide as the nucleophile [12]. For fast reactions where the NMR spectrum of X' differs from that of CH;0:, there is, in principle, another method for determining identity rates.…”

Section: Applicationof the Marcusequationmentioning

confidence: 98%

Methyl Transfer Reaction IX. Linear Free Energy Relations and the Reactivity—Selectivity Principle

Lewis

Douglas

McLaughlin

1985

Israel Journal of Chemistry

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Methyl transfers between nucleophiles are representative and uncomplicated examples of group transfer reactions. Data are shown for rates and equilibria sufficient to allow a nearly rigorous application of the Marcus equation. Selectivities with a series of nucleophiles do not vary significantly with reactivity over a wide range of reactivities, except for diffusion controlled reactions. The Marcus equation, for which the necessary data are now available to calculate the rate, fits very well in cases to which it has been applied. It is shown that the (quadratic) Marcus equation is expected to be compatible with experimental linear free energy relations for most reactions; generally only very fast reactions will reveal the curvature, thus the Hammond postulate, the reactivity—selectivity principle, the variable transition state and the Marcus equation are not incompatible with linear free energy relations.

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Cage effects in the photochemistry of (S)-(+)-2-phenylpropiophenone

Cited by 48 publications

References 0 publications

Systematic structural modifications in the photochemistry of .beta.,.gamma.-unsaturated ketones. II. Acyclic olefins and acetylenes

Systematic structural modifications in the photochemistry of .beta.,.gamma.-unsaturated ketones. II. Acyclic olefins and acetylenes

Rate‐equilibrium LFER characterization of transition states: The interpretation of α

Methyl Transfer Reaction IX. Linear Free Energy Relations and the Reactivity—Selectivity Principle

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