ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 29, Number 6
JKCSEZ 29(6)
December 20, 1985 

The rates of reaction between 4-substituted-2,6-dinitrochlorobenzenes with para-substituted anilines in methanol-acetonitrile mixtures were measured by conductometry. It was observed that the rate constant increases in the order of X = 4-NO2 〉4-CN 〉4-CF3, where X is a substituent in the substrate. The rate constant also increases in the order of Y = p-OCH3 〉p-CH3 〉H 〉p-Cl 〉m-NO2, where Y is a substituent in the aniline ring. Kinetic studies in the methanol-acetonitrile solvent system with various nucleophiles showed that the N-C bond forming step is making a great contribution to the overall second order rate constant. The electrophilic catalysis by methanol probably consists of the hydrogen bonding between alcoholic hydrogen and leaving chloride in the transition state. The nucleophilic catalysis by methanol may be ascribed to the formation of hydrogen bonds between alcoholic oxygen and hydrogens of amines in the transition state. All these experimental facts are supporting the operation of SNAr machanism with the second step being the rate determining. This mechanism can be successfully fitted to the PES model.