SOLVATION EFFECT ON THE PROTON-TRANSFER COMPLEX-FORMATION BETWEEN 2,4-DINITRO-1-NAPHTHOL AND AMINES

The equilibrium constants for the proton transfer complex formation K- eq of 2,4-dinitro-1-naphthol (DNN) with some amines in benzene-dimethy lformamide, ethyl acetate, dioxane, and acetonitrile mixed solvents we re measured. The sharp increase in K-eq for the reaction of DNN with p rimary and secondary amines suggests the formation of a hydrogen bond between the amine hydrogen(s) and the electron-donating solvents. A li near correlation between K-eq, for the DNN-DEA reaction, and Taft's be ta parameter is found except for dioxane. The increase in the equilibr ium constants between DNN and TEA is explained on the grounds of a lon g-range solvation effect. It is shown that K-eq in these systems is qu alitatively related to the dielectric constant (epsilon) and Taft's pi parameters of the solvents used. It is found that the short-range sol vation effect increases K-eq more sharply than the long-range one.