Limitations of the s(E+N) and Related Equations: Solvent Dependence of Electrophilicity

Abstract

electrophilicity · kinetics · linear free-energy relationships · nucleophilicity · solvent effects Generic expressions that capture the essence of reactivity patterns still have important roles, despite the huge advances in computational chemistry for individual systems.[1, 2] New generic equations are relatively rare, and critical scrutiny of the scope and reliability of two such equations [Eqs. (1) and (2)] is presented below. log k ¼ s ðE þ NÞ, or changing the symbol for sThe s(E+N) equation [Eq.(1)] has been developed empirically from constant selectivity relationships [3,4] to correlate logarithms of rate constants (log k) at 208C for a huge range of reactions of electrophiles (electrophilicity E) and nucleophiles (nucleophilicity N); in Equation (1), s (or s N ) [5][6][7] is referred to as a "nucleophile-specific" parameter, [7] and in Equation (2), s E is an "electrophile-specific" parameter.

Reply to T. W. Bentley: Limitations of the s(E+N) and Related Equations

“…[4] and Ref. [1] now pretend that our basis correlation was restricted to electrophiles in the narrow range of 0 < E < 6. This is not true!…”

“…Three of the articles in references [1][2][3][4] carry the term s(N+E) in their title and severely argue against the floating reference scale associated with Equation (1). As pointed out above, Equation (2) is mathematically equivalent to Equation (1).…”

“…We studied the kinetics of their reactions with various nucleophiles and performed a least-squares minimization on the basis of Equation (1). [7a,b] In this equa-…”

“…None of these publications reports new experimental results, and all deal exclusively with a reinterpretation of our kinetic data. As the detailed analysis of the manifold mistakes and incorrect statements in references [1][2][3][4] would bore the nonspecialist reader, I will comment the most important points in this response and ask the interested reader to find my comprehensive reply in the Supporting Information, which also provides a detailed validation of the statements in this reply. Let me first explain the essence of the controversy, which is not described in reference [1].…”

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electrophilicity · kinetics · linear free-energy relationships · nucleophilicity · solvent effectsThe preceding commentary [1] is the forth in a series [2][3][4] that tries to discredit our approach to a semiquantitative model of polar organic reactivity. None of these publications reports new experimental results, and all deal exclusively with a reinterpretation of our kinetic data.

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