Electron donor–acceptor interaction of 3,4-dimethylaniline with 2,3-dicyano-1,4-naphthoquinone

The electron donor–acceptor (EDA) interaction between 2,3-dicyano-1,4-naphthoquinone (DCNQ) and 3,4-dimethylaniline (3,4-DMA) is studied in chloroform, dichloromethane and 1:1 (v/v) mixture of chloroform and dichloromethane. The rate of formation of the product was measured as a function of time using UV–vis spectrophotometer. The formation constant (K) and molar extinction coefficient (ɛ) values for the formation of EDA complex were evaluated in the temperature range of 20–35 °C. The pseudo-first-order rate constant (k1) and the second-order rate constant (k2) for the disappearance of EDA complex and for the formation of product were evaluated. The activation parameters (ΔH#, ΔS# and ΔG#) of the reaction were determined by temperature dependence of rate constants using the Arrhenius plots. The effect of relative permittivity of the medium on the reaction is discussed. The observed results indicate that formation of final product proceeds through initial formation of EDA complex as an intermediate. The product of the reaction was purified by column chromatography method and identified as 3-(N-3,4-dimethyl-phenylamino)-2-cyano-1,4-naphthoquinone by elemental analysis, IR and NMR spectroscopy. On the basis of kinetic, analytical and spectroscopic results, a plausible mechanism for the formation of EDA complex and its transformation into product is proposed.