Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Kinetic isotope effects (KIE) were determined for the reactions of 2-phenylethyl and 1-methyl-2-phenylethyl benzenesulphonates with deuterated aniline nucleophiles in acetonitrile at 65.0 °C. The results are in good agreement with the transition state (TS) structures proposed based on the sign and magnitude of the cross-interaction constants, pxz, between the substituents in the nucleophile (X) and the leaving group (Z). In the reactions of 2-phenylethyl derivatives, all three reaction pathways, kr, kt and kΔ, were found to be contributing competitively; the inverse secondary KIE observed with a stronger nucleophile changed into the primary KIE with a weaker nucleophile owing to the predominant contribution of the four-centre TS in the kf path. For the reactions of the 1-methyl-2-phenylethyl series, the kr path played a major role, the contribution from the front-side nucleophilic attack, kf, being negligible. In both reaction series, the aryl participation was important for the p-CH3O-substituted substrate.
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