Effects of mixed CH3CN(SINGLEBOND)H2O solvents on rate of intramolecular general base-catalyzed cleavage of ionized phenyl salicylate in the presence of 3-aminopropan-1-ol, 1,2-diaminoethane, and glycine

Abstract

The effects of mixed CH 3 CN 9 H 2 O solvents on rates of aminolysis of ionized phenyl salicylate, PS Ϫ , reveal a nonlinear decrease in the nucleophilic second-order rate constants, (for aminolysis) with increase in the content of CH 3 CN until it becomes Ϸ 50%,The values of remain almost unchanged with change in the CH 3 CN content within 50 ms k n to 70 or 80%, v/v. The effects of mixed CH 3 CN 9H 2 O solvents on of leaving group, phenol, pK a and protonated amine nucleophile have been concluded to be the major source for the observed mixed solvent effects on ᭧ 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 301-307, ms k . n 1998.

Effect of mixed H2O−CH3CN solvent on intramolecular general base-catalyzed cleavage of ionized phenyl salicylate in the presence of DL-proline

“…The calculated values of ko and k, m~ at different content of CH3CN are shown in Table 1. But the pK~ ~ of amines such as 3-aminopropan-l-ol and 1,2-diaminoethane showed a slight decrease ( -0.1 pK units) with the increase in CH3CN content from 2 to 50 % v/v [3]. The values of pKa m~ of DL-proline and glycine [3] increased by 0.43 and 0.23 pK units, respectively with the increase in CH3CN content from 2 to 50 % v/v.…”

“…1, using linear least squares technique. The values of pKa m~ of DL-proline and glycine [3] increased by 0.43 and 0.23 pK units, respectively with the increase in CH3CN content from 2 to 50 % v/v. The spectral technique described earlier [3] showed the presence of 100 % ionized form (PS) of phenyl salieylate under the present experimental conditions of entire kinetic runs.…”

“…Almost similar results were obtained for the reactions of PS with 3-aminopropan-l-ol, 1,2-diaminoethane and glycine under similar conditions [3]. But the values ofkn ~ slightly increased with increasing content of CH3CN from 50 to 70 % v/v.…”

“…The concentration ionization constant, K~, of conjugate acid of DL-proline were determined at 35~ in mixed HzO-CH3CN solvents by potentiometric technique as described elsewhere [3]. The concentration ionization constant, K~, of conjugate acid of DL-proline were determined at 35~ in mixed HzO-CH3CN solvents by potentiometric technique as described elsewhere [3].…”

“…The effect of micelles on the reaction rate may be described in terms of several factors including the decrease in polarity of the micellar pseudophase in comparison with that of the aqueous pseudophase [6]. The effects of mixed waterorganic solvents on the rates of hydrolysis [7], alcoholysis [8] and aminolysis [3] of PS-have been studied. The effects of mixed waterorganic solvents on the rates of hydrolysis [7], alcoholysis [8] and aminolysis [3] of PS-have been studied.…”