FACTORS INFLUENCING S-O BOND AND C-O BOND CLEAVAGES IN THE REACTIONS OF 2,4-DINITROPHENYL X-SUBSTITUTED BENZENESULFONATES WITH VARIOUS NUCLEOPHILIC-REAGENTS

Second-order rate constants have been measured spectrophotometrically for the reaction of 2,4-dinitrophenyl X-substituted benzenesulfonates with Z-substituted phenoxides in absolute ethanol at 25.0+/-0.1 degree s C. The nucleophilic substitution reaction gives both S-O bond and C- O bond cleavage products. The extent of S-O bond cleavage increases si gnificantly with increasing electron withdrawing ability of the sulfon yl substitutent X, while that of the C-O bond cleavage is independent on the electronic effect of the substituent. On the contratry, the eff ect of the substituent Z in the nucleophilic phenoxide is more signifi cant for the C-O bond cleavage than for the S-O bond cleavage. Aminoly ses of 2,4-dinitrophenyl benzenesulfonate (1) with various 1 degrees, 2 degrees and 3 degrees amines have revealed that steric effect is lit tle important. The extent of S-O bond cleavage increases with increasi ng the basicity of the amines, but decreases with increasing the basic ity of the nucleophilic aryloxides, indicating that the HSAB principle is not always operative. Besides, reactant and solvent polarizability effect has also been found to be an important factor in some cases bu t not always to influence the reaction site.