Multiple structure–reactivity relationships for a Menschutkin-type SN2 reaction

Abstract
The mechanisms of nucleophilic displacement was studied by using three variable systems of ρX, ρY, and ρZ obtained from the change of substituents X, Y, and Z for the reaction of (Z)-substituted benzyl (X)-benzenesulphonates with (Y)-substituted N,N-dimethylanilines in acetone at 35 °C. The coefficient of the interaction term, ρXY, has a value of 0.21 which means that bond-making and -breaking are concerted in the SN2 transition state. In the range Z = H to p-NO2, in which the SN2 mechanism is predicted to be dominant, the |ρZY| value is very large, 0.5, which means that the interaction between Z and Y is very large. |ρZX| is ca. 0.06 which means that the interaction is small between X and Z. In contrast, in the range Z = H to p-Me, in which the SN1 mechanism is dominant, the |ρZY| value is nearly zero, indicating no interaction between Z and Y. Changes of substituent effect and interaction terms, ρXY, ρYZ, and ρZX are useful tools for distinguishing wrong reaction mechanisms.

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