Effect of substituents in phenol and aniline nucleophiles on activation parameters in SNAr reactions

摘要

Changes of activation parameters, Delta H-not equal and Delta S-not equal with or constants of substituents in the phenol and aniline nucleophiles for their SNAr reactions in various solvents give the delta Delta H-not equal and delta Delta S-not equal reaction constants which are linearly related. The dependence obtained, delta Delta H-not equal versus delta Delta S-not equal, allow estimation of the contribution of changes of the internal enthalpy, delta Delta H-int(not equal), to the enthalpy reaction constant, delta Delta H-not equal, which give a linear dependence on the Hammett reaction constants, rho. The results obtained show that the substituent effects on the charge development in the transition state (TS) are governed by the magnitude of delta Delta H-int(not equal). Copyright