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Alkali-metal ion catalysis and inhibition in nucleophilic displacement reaction of O-ethyl O-4-nitrophenyl phenylphosphonothioate with alkali-metal ethoxides

Title
Alkali-metal ion catalysis and inhibition in nucleophilic displacement reaction of O-ethyl O-4-nitrophenyl phenylphosphonothioate with alkali-metal ethoxides
Authors
Um I.-H.Kang J.-S.Shin M.
Ewha Authors
엄익환
SCOPUS Author ID
엄익환scopusscopus
Issue Date
2013
Journal Title
Bulletin of the Chemical Society of Japan
ISSN
0009-2673JCR Link
Citation
vol. 86, no. 6, pp. 736 - 741
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
A kinetic study on nucleophilic displacement reactions of O-ethyl O-4-nitrophenyl phenylphosphonothioate (an insecticide called EPN) with alkali-metal ethoxides (EtOM; M = Li, Na, K, and K/18-crown-6-ether) is reported. Dissection of pseudo-first-order rate constant (kobsd) into the second-order rate constants for the reaction of EPN with the dissociated EtO- (kEtO-) and ion-paired EtOM (kEtOM) has revealed that the reactivity increases in the order kEtOLi < kEtO < kEtONa < kEtOK < k EtOK/18-crown-6-ether, indicating that Li+ inhibits the reaction while the other M+ ions behave as a Lewis acid catalyst in the order Na+ < K+ < 18C6-complexed K+. The contrasting M+ ion effects have been explained in terms of the hard and soft acids and bases (HSAB) principle, since EPN, as a polarizable P=S centered electrophile, would exert a weak interaction with Li+ (a hard acid) but a strong interaction with the 18C6-complexed K+ ion (a soft acid). M+ ions catalyze the current reaction by increasing the electrophilicity of the reaction center. EPN is less reactive than O-4-nitrophenyl diphenylphosphinothioate but is more reactive than O-4-nitrophenyl O,O-diethyl thiophosphate. Factors governing the reactivity of these P=S centered electrophiles are discussed. © 2013 The Chemical Society of Japan.
DOI
10.1246/bcsj.20130015
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자연과학대학 > 화학·나노과학전공 > Journal papers
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