Infrared absorption spectra of some bases of the pyridine series

Summary

• 1. Comparison of the infrared spectra of compounds of the α-aminopyridine and α-pyridonimine series shows that the more basic nitrogen atom in these compounds is that bound by a double bend; this nitrogen atom functions as a salt-forming center.

• 2. It is established that in α-pyrolamine derivatives addition of a proton at the side-chain (inane) nitrogen atoms residue in a redistribution of electron density with formation of a molecule of “benzenoid” structre, In salts of bases of the α-aminopyridine of N-alkyl-α-pyridonimine type ,the positive charge is probably distributed between both nitrogen atoms, the greater share of the charge being concentrated on the ring nitrogen in both cases. The

  

  , groups formed in salts of this type differ in nature (valency state of the nitrogen atom) from the the NH₂ groups of α-aminopyridine or aniline.

• 3. It is probably that in the crystalline state, salts of the aniline hydrochloride type are not true salts characterized by the ionic structure-NH₂Cl but are stable satellite molecular compounds.