INFRARED SPECTRA OF PYRROLES AND DIPYRRYLMETHANES

Abstract

The IR spectra of 18 substituted pyrroles and 6 substituted dipyrrylmethanes are investigated. It is shown that the position of the valence vibrations frequency of the free NH group, ν_free NH depends on the number of substituents in the ring. The frequency is influenced by the electronegativity of a substituent, the effect of an α- being much more marked than that of a β-substituent. The stability of the hydrogen bond increases with increase in substituent electronegativity. When two electronegative substituents occupy the α and β positions, they have a mutually weakening effect. The ν_C=O (acetyl) absorption bands in pyrrolecontaining compounds are situated 40–60 cm⁻¹ lower than in aromatic ketones and greatly depend on the position and nature of the substituent in the pyrrole ring.

Authors: A. F. Mironov, L. D. Miroshnichenko, R. P. Evstigneeva, N. A. Preobrazhenskii.

English Translation in Chemistry of Heterocyclic Compounds, 1965, 1 (1), pp 49-53

http://link.springer.com/article/10.1007/BF01168919