Kinetics and Mechanism of the Reaction of para-Chlorophenyl aryl Chlorophosphates with Pyridines in Acetonirrile

초록

The Kinetics and mechanism of the pyridinolysis of p-chlorophosphates (1) have been carried out in MeCN at 5℃. Lee and coworkers have reported wxperimentally its (1) aminolysis (Lee et al ; Int. J. Chem. Kinet., 2002, 34, 632-637). All the results (rx, ry, bx, rxy, Kinetcis isptope effects and activation parameters) are consistent with a concerted nucleophilic substitution mechanism. The second-order rate constant for substitutions for substituents at substrate, Y=H, ρ-CH3, ρCH3O were observed for this reaction. The rates are found faster for the pyridinolysis than sit aminolysis. bx values are smaller in this work (1.14 ~ 1.17) than. the aminolysis (1.43 - 1.49) indicating less degreeof bound formation in TS during pyridinolysis. rx (-5.72 ~ -5.80) supports +ve charge development in reaction center alike aminolysis, rx (-4.04 ~ -4.24). Relatively low △H1 (2.5 - 4.7 Kcal mol-1) and large negative △S1 values (-49 ~-54 cal mol-1K-1) are whthin the typical range of SN2 reaction. Our interest is comparative mechanistic inverstigation changing nucleophile from primary to tertiary amine.