Table 3.

Chemical identification of the faint-yellow crystal from the spectrum of FTIR

Wavenumber (cm−1)	Main attributes	Functional group
2 500‒3 000 (m)	‒O‒H stretching vibration	‒COOH
1 645 (s)	‒C=O stretching vibration	‒O‒C=O
1 621 (s)	‒C=C stretching vibration	‒O‒C=O
960‒980 (m)	=C‒H out-plane bending vibration	Ar‒C=C
3 239 (w)	Benzene ring =C‒H stretching vibration	Benzene ring
1 524 (s)	Benzene ring C=C stretching vibration	Benzene ring
665‒900 (m)	Benzene ring =C‒H out-plane bending vibration	Benzene ring
3 437 (s)	‒O‒H stretching vibration	Phenol OH
1 353 (s)	‒O‒H bending vibration	Phenol OH
1 220 (m)	‒C‒OH stretching vibration	Phenol OH