The protonation of some 3-substituted 2-(N,N-dialkylamino)-5-nitrothiophenes

Abstract

The protonation of some 3-substituted 2-(N,N-dialkylamino)-5-nitrothiophenes (3)–(4) and some 5-substituted 3-nitro-2-piperidinothiophenes (2) has been studied in aqueous perchloric and/or sulphuric acid. pK_BH⁺ values have been calculated according to modified Hammett, Bunnett–Olsen, and Marziano–Yates–Cox methods and the data obtained related to the effect of the substituents. The results obtained have been discussed considering the different interactions that the dialkylamino (N,N-dimethylamino or piperidino) group at C-2 can give with the group (nitro-group or variable substituent) present at C-3 (an ortho-like position).