NITRIMINO-(1H)PYRIDINIUM AND NITRIMIN0-(3H)THIAZOLIUM INNER SALTS: THE STRUCTURE OF SOME NITRIMINES IN THE LIGHT OF INFRARED STUDY

Abstract

Compounds previously known as nitraminopyridines and 2-nitraminothiazoles are formulated as nitrimino-(1H)pyridinium and 2-nitrimino-(3H)thiazolium inner salts on the basis of the infrared study. In the solid state, the three isomer nitriminopyridines do not exhibit any infrared absorption of the —NH group in the region 3400–3200 cm.⁻¹ but show a wide band at lower frequencies in the region 2880–2550 cm⁻¹. 2-Nitriminothiazole shows only a wide band between 3140 and 2270 cm.⁻¹. These shifts of absorption bands can be correlated with structures derived from the classical nitrimino tautomeric forms in which the resonance effect stabilizes (1H)pyridinium and (3H)thiazolium cations, and a nitrimino group carrying a negative charge. n-Butylnitramine, a non-resonating compound, absorbs strongly at 3300 cm.⁻¹, indicating that nitramino groups are not associated.