Kinetics of the ruthenium (III) catalyzed oxidation of amides by sodium N-Bromotoluenesulfonamide in hydrochloric acid solution

摘要

The kinetics of Ru (III) catalyzed oxidations of urea,methylurea and ethylurea by sodium N-bromo-p-toluenesulfonamide, also known as bromamine-T (BAT), in HCIsolution has been studied at 30℃. The reaction rate shows a first-order dependence each on [BAT], [amide] and [Ru (III)] andfractional-order on [H+]. Additions of halide ions and the reactionproduct of BAT (p-toluenesulfonamide) and the variation of ionicstrength and dielectric constant of the medium do not have anysignificant effect on the reaction rate. Activation parameters havebeen evaluated. A Taft linear free energy relationship is observedfor the reaction, with P*=-0.64 and –2.95 and δ=-0.25,indicating that electron donating groups enhance the rate. Anisokinetic relationship is observed with β=391K indicating thatenthalpy factors control the rate. The existence of the relationshiphas been supported by the Exner criterion. The protonationconstant of monobromamine-T calculated from a plot of 1/k'versus 1/[H+] is 29.15. mechanisms consistent with the observedkinetic data have been proposed.