AROMATIC NUCLEOPHILIC-SUBSTITUTION REACTIONS OF SOME 2-L-3-NITRO-5-X-THIOPHENES WITH PIPERIDINE AND ANILINE IN METHANOL - SUBSTITUENT CONSTANTS FOR THE THIOPHENE SYSTEM

The rate constants for the reactions of some 2-L-3-nitro-5-X-thiophene s 1-4 with aniline and of compounds (4) with piperidine in methanol ha ve been measured at various temperatures. By using the data obtained i n this work as well as previously available data sets, a series of opt imized 'thiophene' sigma gamma values has been calculated. The suscept ibility constants p(L) of the various sets have been analysed in the f ramework of the reactivity-selectivity principle.