CATALYSIS IN AROMATIC NUCLEOPHILIC-SUBSTITUTION - PART 12 - KINETICS OF THE REACTIONS OF SOME 2-PHENOXY-3-NITRO-5-X-THIOPHENES AND 2-(P-NITROPHENOXY)-3-NITRO-5-X-THIOPHENES WITH BENZYLAMINE AND N-BENZYLMETHYLAMINE IN BENZENE

The rate constants of the title reactions have been measured in benzen e at 20 degrees C. The reactions with benzylamine are not base-catalys ed. The second-order kinetic constant for the reactions with N-benzylm ethylamine, with the exception of the unsubstituted compound (X = H), increases in a hyperbolical way with increasing nucleophile concentrat ion. A non-linear regression treatment of kinetic data allows the calc ulation of k(1) and k(3)(B)/k(-1) for each catalysed system, k(3)(B)/k (-1) is not a monotonic function of the X substituent. This result has been rationalised on the grounds of a specific base-general acid (SB- GA) mechanism for the base catalysis.