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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 15, Number 2
BKCSDE 15(2)
February 20, 1994 

The Effect of Alkali Metal Ions on Nucleophilic Substitution Reactions of Aryl Substituted Benzenesulfonates
Ik-Hwan Um*, Seok-Joo Lee, Hee-Sun Park, Dong-Sook Kwon
Rate constants have been measured spectrophotometrically for the nucleophilic substitution reactions of aryl substituted benzenesulfonates (3) with alkali metal ethoxides (EtO-M+) and butane-2,3-dione monoximates (Ox-M+) in ethanol at 25 ℃. The reactivity of the alkali metal ethoxides decreases in the order EtO-K+ > EtO- > EtO-Li+, indicating that K+ ion behaves as a catalyst and Li+ ion acts as an inhibitor for all the substrates studied. For the corresponding reactions of 3 with Ox-M+, Li+ ion also exhibits inhibitory effect for all the substrates, while, K+ ion shows catalytic or inhibitory effects depending on the nature of substituents on the acyl and phenyl moieties. A study of substituent effect on rate has revealed that both EtO- and Ox- systems have the same reaction mechanism. The different behavior shown by K+ ion for the reaction of 3 with EtO- and Ox- would be attributed to a difference in charge polarization of S=O bond in the transition state between the two systems and/or a change in conformation of Ox-K+.
161 - 167
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