Association and relative acidities of 2-substituted 5-trifluoroacetylpyrroles

The acidities of 2-substituted 5-trifluoroacetylpyrroles were studied by IR spectroscopy from the shift of the frequency of the NH stretching vibration (_NH) in the presence of dimethylformamide (DMF) relative to the band of vibrations of free NH. The existence of a correlation relationship between _NH and _I constitutes evidence that the acidities of pyrroles are determined primarily by the inductive effect of the substituents in the 2 and 5 positions of the pyrrole ring. The low probability of the formation of an intramolecular NH... O=C hydrogen bond in the investigated molecules was demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 772–774, June, 1984.