The structure in the solid state and in solution of 3(5)-trifluoromethyl-4, 5(3)-polymethylenepyrazoles

Abstract

The tautomerism of three polymethylenepyrazoles bearing at position 3(5) a trifluoromethyl group has been studied by NMR in solution (1H, 13C, 15N, 19F) and in the solid state ( 13C, 15N). The conclusion is that in all cases they are 3-CF3 tautomers. DFT calculations have been carried out to compare these compounds to the analogous 3-CH3 derivatives and to assess the Mills-Nixon effect in the case of trimethylene derivatives as well as the effect of replacing a CH3 by a CF3 group on the tautomerism.