Solute–solvent interaction effects on second‐order rate constants of reaction between 1‐chloro‐2,4‐dinitrobenzene and aniline in alcohol–water mixtures

The second‐order rate coefficients for aromatic nucleophilic substitution reaction between 1‐chloro‐2,4‐dinitrobenzene and aniline have been measured in aqueous solutions of ethanol and methanol at 25°C. The plots of rate constants versus mole fraction of water show a maximum in all‐aqueous solutions. The effect of four empirical solvent parameters including hydrogen bond donor acidity (α) dipolarity/polarizability (π * ) normalized polarity ( E N T ) and solvophobicity ( Sp ) has been investigated. This investigation has been carried out by means of simple and multiple regression models. A dual‐parameter equation of log k 2 versus Sp and α was obtained in all‐aqueous solutions ( n = 41, r = 0.962, s = 0.053, p = 0.0000). This equation shows that solvophobicity and hydrogen bond donor acidity are important factors in the occurrence of the reaction and they have opposite effects on reaction rate. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 90–97, 2005