The reaction rates of 4-X-2,6-dinitrochlorobenzenes (X = $NO_2,;CN,;CF_3$) with Y-substituted pyridines (Y = 3-$OCH_3,;H,;3-CH_3,;4-CH_3$) in methanol-acetonitrile mixtures were measured by conductometry at 25 ${^{circ}C}$. It was observed that the rate constant increased in the order of X = 4-$NO_2;>;4-CN;>;4-CF_3$ and the rate constant also increased in the order of Y = 4-$CH_3;>;3-CH_3;>;H;>;3-OCH_3$. When the solvent composition was varied, the rate constant increased in order of MeCN > 50% MeOH > MeOH. The electrophilic catalysis by methanol may be ascribed to the formation of hydrogen bonds between alcoholic hydrogen and nitrogen of pyridines in ground state. Based on the transition parameters, ${ ho}_S,;{ ho}_N,;{eta}_Y,;{ ho}_{XY}$ and solvent effects, the reaction seems to proceed via $S_N$Ar-Ad.E mechanism. We also estimated the isokinetic solvent mixtures (${ ho}_{XY}$ = 0) based on cross-interaction constants, where the substituent effects of the substrate and nucleophile are compensated.