Kinetics and Mechanism for the Reaction of 4-Nitrophenyl 2-Thiophenecarboxylate with Secondary Alicyclic Amines

摘要: Second-order-rate constants (k N ) have been measured spectrophotometrically for the reactions of 4-nitrophenyl 2-thiophenecarboxylate (la) with a series secondary alicyclic amines in H 2 O containing 20 mole % DMSO at 25.0 °C. The ester la is less reactive than 2-furoate (1b) but more benzoate (1c) except towards piperazinium ion. Bronsted-type plots aminolyses la, 1b and 1c are linear β n u c value 0.92, 0.84 0.85, respectively, indicating that replacement CH=CH group by sulfur or an oxygen atom benzoyl moiety does not cause any mechanism change. reaction piperidine substituted phenyl 2-thiophenecarboxylates gives Hammett plot large ρ - (ρ = 3.11) when σ used. Bronsted values suggest aminolysis proceeds via rate-determining break-down addition intermediate to products.