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Li, Zhen; Chen, Quan; Mayer, Peter; Mayr, Herbert (2017): Nucleophilicity Parameters of Arylsulfonyl-Substituted Halomethyl Anions. In: Journal of Organic Chemistry, Vol. 82, No. 4: pp. 2011-2017
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The rates of the reactions of the arylsulfonyl-substituted carbanions carrying a-chloro and a-bromo substituents (1a-e) with quinone methides 2a-g and benzylidenemalonates 2h and 2i in DMSO were determined photometrically at 20 degrees C. The reactions were performed under pseudo-first-order conditions, and the second-order rate constants were obtained as the slopes of the plots of the pseudo-first-order rate constants versus the concentrations of the reactants used in excess. The second order rate constants correlate linearly with the parameters E of the reference electrophiles according to the linear free energy relationship log k(2)(20 degrees C) = s(N)(N + E), which allowed us to derive the nucleophile-specific parameters N and s(N) of carbanions la-e. The resulting nucleophilicity parameters N (23 < N < 29) reveal the title compounds to be among the most reactive nucleophiles so far integrated on our comprehensive nucleophilicity scale.