87962-88-7Relevant articles and documents
Kinetics and Equilibria of Ring Closure through an Amide Linkage. Part 2. 1-Aryl-2-pyrrolidones
Abdallah, Jassim M.,Moodie, Roy B.
, p. 1243 - 1250 (2007/10/02)
Equilibrium constants, and rate constants for forward and reverse reactions, for ring closure of several 4-(arylamino)butanoic acids to 1-aryl-2-pyrrolidones in aqueous acid, together with ionisation constants of the former group of compounds, are reported.The equilibrium constants K at 50 deg C between neutral protonic forms of open-chain and ring compounds are related to the ionisation constants of the nitrogen-protonated 4-(arylamino)butanoic acids, K1, by the equation: log K=0.70 (pK1)+1.53.The value of K for pyrrolidone itself was measured for comparison.Studies of 18O exchange reveal that (except in the case of the substrate which bears the most electron-withdrawing substituents in the aryl ring, namely 2,4-dinitro) the rate-determining step lies between the tetrahedral intermediate and the ring compound.Substituent effects and solvent deuterium isotope effects on the hydronium-ion catalysed reaction are consisitent with a transition state close to the neutral tetrahedral intermediate.The effects of methyl substituents in the heterocyclic ring on rate and equilibrium constants have also been studied.The variation of K with temperature, and derived thermodynamic parameters, are reported in two cases.
