On the basis of the IR spectra of arylhydrazones 2 and 4, it
was possible to assign the absorption bands of the diazonium
coupling products 2 and 4. Each of the compounds investigated
possessed a weak and broad band in the region 3100–3300 cm−1.
This was assigned to NH stretching of the hydrazone moiety. The
large shift and broadening of this band, as reported by Ramirez and
Kirby [15], for simple hydrazones, can result only from intramolecular
hydrogen bonding as in (C). The fact that the compounds
2 and 4 show evidence for intramolecular hydrogen bonding is
in favor of the hydrazone structure. The IR spectra of all compounds
showed absorption bands in the region 2220–2222 cm−1.
These bands assigned to C N vibration. So, on the basis of these
data, structure (B) can be ruled out. The IR spectra of almost all