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Cross‐interaction constants as a measure of the transition state structure. Part 15. Kinetic isotope effects in the S N 2 reactions of 2‐phenylethyl derivatives with deuterated aniline nucleophiles
Author(s) -
Lee Ikchoon,
Koh Han Joong,
Lee Hai Whang
Publication year - 1991
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610040206
Subject(s) - chemistry , nucleophile , kinetic isotope effect , aniline , deuterium , reaction rate constant , medicinal chemistry , transition state , stereochemistry , aryl , acetonitrile , computational chemistry , organic chemistry , kinetics , catalysis , physics , alkyl , quantum mechanics
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, k r , k t and k Δ , 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 k f path. For the reactions of the 1‐methyl‐2‐phenylethyl series, the k r path played a major role, the contribution from the front‐side nucleophilic attack, k f , being negligible. In both reaction series, the aryl participation was important for the p ‐CH 3 O‐substituted substrate.