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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 13, Number 6
BKCSDE 13(6)
June 20, 1992 

The Effect of Solvation and Polarizability on the α-Effect : Nucleophilic Substitution Reactions of p-Nitrophenyl Benzoate with Various Anionic Nucleophiles
Ik-Hwan Um
Second-order rate constants have been determined spectrophotometrically for nucleophilic substitution reactions of p-nitrophenyl benzoate with various anionic nucleophiles including 6 α -effect nucleophiles. The logarithmic second-order rate constants for the aryloxides give a good Bronsted correlation with the respective basicity while the ones for p-chlorothiophenoxide and hydroxide exhibit significantly positive and negative deviations, respectivity, from the Bronsted linear line. The deviations are attributed to a solvation effect rather than a change in the reaction mechanism. The α-effect nucleophiles except highly basic ones demonstrate significantly higher nucleophilicity (the α -effect) than would be predicted from the respective basicity. The effect of solvation and polarizability appears to be important for the α -effect as well as for the reaction rate.
632 - 636
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