Aminolysis of 2,4-Dinitrophenyl and 3,4-Dinitrophenyl Benzoates: Effect of ortho-Nitro Group on Reactivity and Mechanism

摘要: Second-order rate constants () have been measured spectrophotometrically for reactions of 3,4-dinitrophenyl benzoates (5b) with a series alicyclic secondary amines in 80 mol % /20 DMSO at 25.0 0.1 . The kinetic data compared the reported previously corresponding 2,4- dinitrophenyl (5a) to investigate effect changing nucleofuge from 2,4-dinitrophenoxide 3,4-dinitrophenoxide on reactivity and mechanism. results show that aminolyses 5a 5b proceed through same mechanism, i.e., zwitterionic tetrahedral intermediate change rate-determining step (RDS). Substrate is more reactive than when breakdown RDS but less formation RDS. Dissection kN values into microscopic (e.g., ratio) has revealed larger ratios smaller k1 all studied. Since basic better 3,4-dinitrophenoxide, determined those are as expected. steric hindrance exerted by ortho-nitro group contributes found 5b.