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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 16, Number 9
BKCSDE 16(9)
September 20, 1995 

Tightness of the Transition State for the Reactions of Secondary Alkyl Arenesulfonates with Anilines in Acetonitrile
Hyuck Keun Oh, Young Bong Kwon, Dong Soo Chung*, Ikchoon Lee*
Kinetic studies on the reactions of five secondary acylic alkyl arenesulfonates with anilines are carried out in acetonitrile at 65.0 ℃. The magnitude of ρXZ determined (ρXZ=0.12-0.13) is slightly greater than that for the alicyclic series (ρXZ=0.11) under the same experimental condition. Ab initio MO results are found to support the slightly tighter transition state expected from the greater magnitude of ρXZ for the acyclic series. Despite the small variations, the magnitude of ρXZ and the theoretical transition state tightness remain relatively constant for the secondary carbon centers. Secondary kinetic isotope effects involving deuterated aniline nucleophiles show a successively smaller kH/kD(<1.0) value for a more sterically crowded reaction center carbon. This is in accord with the later transition state for bond-making predicted by the Bell-Evans-Polanyi principle for the more endothermic nucleophilic substitution reaction. Further support is provided by the results of the AM1 MO calculations on the reactions of secondary alkyl benzenesulfonates with chloride nucleophile.
827 - 831
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