Synthesis and chemistry of azolenines. Part 19. Basicities of some 2 H ‐ and 3 H ‐pyrroles and the remarkably large p K a ′ of 2,2,3,5‐tetramethyl‐2 H ‐pyrrole

p K a ′ Values are reported for two 2 H ‐pyrroles and their 3 H ‐pyrrole isomers. The latter have basicities of the same order as similarly substituted pyridines, whereas the former are 2–2·5 p K units more basic, 2,2,3,5‐tetramethyl‐2 H ‐pyrrole having a p K a ′ of 8·40, close to that for 2‐aminoimidazole. Possible reasons are given.