Pyrrole studies. Part XIV. Spectroscopic characteristics of cyanopyrroles

Abstract

Data for pyrroles containing methyl and cyano-groups show that the NH stretching frequency may be represented by the equation: ν_NH(cm.^–1)= 3496 – 9n_αCH₃+ 2n_βCH₃– 22n_αCN – 12n_βCN where n_α and n_β are the number of substituents in the α- and β-positions respectively. The electronic spectra indicate that in the excited state the resonance stabilisation by the α-cyano-group is greater than that of the β-cyano-group to the extent of ca. 10·5 kcal./mole.