Abstract
In non-polar solvents, primary and secondary amines undergo self-aggregation, the predominating contributor is the dimeric amine. Several authors attribute this dimer as the crucial nucleophile in aminolyses of carboxylic esters as well as in SNAr reactions in these solvents. The present authors undertook the probe reactions with aniline in benzene. Kinetic data can be reproduced in a dimer-nucleophile framework. A necessary condition of the dimer-nucleophile mechanism is that, as the aggregation is a preequilibrium in the reactions, a sole and a common equilibrium constant should be held for an amine in a given solvent at a given temperature irrespective of the change of reaction substrates.In SNAr reactions with 2,4-dinitrohalobenzenes and 2,4,6-trinitrohalobenzenes, however, no unique and a common formation constant for aniline dimer can be derived. (scatter between 1.17 and 0.00232 mol-1 dm3)In Michael addition-elimination reactions of ethyl trifluoroacetylvinyl ether, a formation constant for aniline dimer (3.68 mol-1 dm3) can be derived, which again would not coincide with those found in SNAr reactions. One is now in a position to look for an alternative mechanism that accords with the kinetic data hitherto obtained and the data for the reactions with phenyl trifluoroacetylvinyl solfone which are to be given in this work.
