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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 15, Number 10
BKCSDE 15(10)
October 20, 1994 

The Effect of Polarizability on Reactivity of 4-Nitrophenyl Benzoate and Its Sulfur Containing Analogues with Anionic Nucleophiles in Ethanol
Dong-Sook Kwon, Jee-Young Park, Ik-Hwan Um*
2nd-order rate constants have been measured spectrophotometrically for the reactions of 4-nitrophenyl benzoate (1), S-4-nitrophenyl thiobenzoate (2) and 4-nitrophenyl thionbenzoate (3) with alkoxides, aryloxides and thioaryloxides in absolute ethanol at 25.0 ±0.1 ℃. The substitution of O by polarizable S in the leaving group has little affected the reactivity of 2 toward the charge localized species (eg. EtO- and CF3CH2O-), while the effect of the similar replacement in the carbonyl group has led to a decrease in reactivity by a factor of 10. However, the reactivity of these esters toward charge delocalized aryloxides has been found to be in the order 1<3≤2. The effect of replaced sulfur atom on reactivity becomes more significant for the reaction with polarizable thioaryloxides, i.e. the reactivity increases in the order 1 < 2 ≪ 3. The difference in reactivity for the present system is attributed to a polarizability effect.
860 - 864
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