BAND ASSIGNMENTS OF THE INFRARED-SPECTRUM OF 1-METHYL-2(1H)-PYRIDINIMINE

The band assignments of the IR spectrum of 1-methyl-2(1H)-pyridinimine in solution were carried out with the normal coordinate treatment by the ab initio 6-31G method. The IR spectrum of the compound is charact erized by three prominent strong absorption bands in the 1700 to 1500 cm-1 region. These three bands are mainly attributed to the stretching modes of the C=C bonds of the ring and the C=N group. All another ban ds are relatively weak compared with the intensities of these bands. T he normal coordinate treatment suggests that 1-methyl-2(1H)-pyridinimi ne has three out-of-plane fundamental bands in the frequency region lo wer than the lowest fundamental band of pyridine. The calculated lowes t fundamental band is near 129 cm It was assigned to the twisting mode of the CH3 group. The second and third lowest bands correspond to the twisting vibration of the CH3 group and the out-of-plane bending vibr ation of the ring framework. This suggests that the ring framework of 1-methyl-2(1H)-pyridinimine may be more flexible than that of pyridine . The vibrational features of the IR spectrum of 1-methyl-2(1H)-pyridi nimine are similar to that of 1-methyl-2-pyridone. In the liquid state , 1-methyl-2(1H)-pyridinimine forms an inter-molecular hydrogen bond b etween the imino groups.