Kinetics and mechanism of nitration of aromatic compounds using trichloroisocyanuric acid (TCCA)/NaNO2, TCCA‐N,N‐dimethyl formamide (TCCA‐DMF)/NaNO2, and TCCA‐N,N‐dimethyl acetamide (TCCA‐DMA)/NaNO2 under acid‐free and Vilsmeier‐Haack conditions. Reactions followed second‐order kinetics with a first‐order dependence on [Phenol] and [Nitrating agent] ([TCCA], [(TCCA‐DMF)], or [(TCCA‐DMA)] >> [NaNO2]). Reaction rates accelerated with the introduction of electron‐donating groups and retarded with electron‐withdrawing groups, but did not fit well into the Hammett's theory of linear free energy relationship or its modified forms like Brown‐Okamoto or Yukawa‐Tsuno equations. Rate data were analyzed by Charton's multiple linear regression analysis. Isokinetic temperature (β) values, obtained from Exner's theory for different protocols, are 403.7 K (TCCA‐NaNO2), 365.8 K (TCCA‐DMF)/NaNO2, and 358 K (TCCA‐DMA)/NaNO2. These values are far above the experimental temperature range (303‐323 K), indicating that the enthalpy factors are probably more important in controlling the reaction.

This study deals with the synthetic and kinetic aspects of trichloroisocyanuric acid (TCCA) and NaNO 2 mediated nitration of indoles in aqueous acetonitrile media under acid-free and Vilsmeier-Haack conditions (using N,N′-dimethyl amides) conditions. Nitration of indoles revealed second order kinetics, with a first order dependence on [indole] and [nitrating agent] ([TCCA]/[NaNO 2 ], [(TCCA-DMF)]/[NaNO 2 ] or [(TCCA-DMA)]/[NaNO 2 ], in which [NaNO 2 ] far excess over other reagents). Reactions followed overall second order kinetics with first order in [reagent] and [indole] under the experimental conditions. Isokinetic temperature (β) values were obtained from Leffler's equation for different kinetic protocols (β = 303 K (TCCA-NaNO 2 ); 303 K (TCCA-DMF)/NaNO 2 ; and 244 K (TCCA-DMA)/NaNO 2 ). These values are the experimental temperature range (303-323 K) indicating that the entropy factors are probably more important in controlling the reaction.