The kinetics of the coupling of 2-N-(4'-X-pheny1)-4,6-dinitrobenzotriazole 1-oxides 1 a-d (X = OMe, H, Br and CN) with nitroalkyl anions 2 a-c have been investigated in aqueous solution at 20°C. Using the derived second-order rate constants and this series of nucleophiles 2 a-c as reference, the electrophilicity parameters E of the four electrophiles 1 a-d have been determined according to the linear free enthalpy relationship log k (20°C) = s N (E + N). With the electrophilicity parameters E range from À 9.72 to À 11.78, the substituent effects on the electrophilic reactivity was examined quantitatively, leading to linear correlation of E with Hammett substituent constants (σ). Based on this correlation, the unknown electrophilicity parameters E of other 2-N-(4'-X-pheny1)-4,6-dinitrobenzotriazole 1oxides (X = CF 3 , Me and OH) were evaluated. Excellent linear correlation (r 2 = 0.9962) between the electrophilicity parameters E of benzotriazoles 1 a-d and their pK a values for σ-complexation has also been observed and discussed.

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