Table 1.

Vibrational mode assignments for Sudan Red G, yellow turmeric, and white turmeric [36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53].

Sudan Red G	Yellow Turmeric	White Turmeric	Special Assignments
		1635	ν (C=O) stretching polycyclic quinones
	1628		ν (C=C) stretching trans form
1616			ν (C–N) stretching in C=C–N=N
	1603	1605	ν (C=C) stretching out of plane
1554			δ (N-H) bending in Ar–N=N··H–O–Ar’
	1512	1514	δ (Ar–O + Ar–O–R) bending asym
1500			ν (N=N) stretching cis
1483			ν (N=N) stretching trans
1448			ν (N=N) stretching + δ (H–C)
1385			δ (Ar–O + Ar–N–R) bending sym
	1381		δ (OH) bending alcoholic
		1369	δ (H–C) bending in O=C–CH2–C=O
1317			ν (Ar–O) stretching sym in Ar–N=N··H–O–Ar’
1294			ν (C–O)− stretching on deprotonated Ar–O−
	1282		ν (C–O) stretching phenolic
1252		1252	CH bending
	1234		CH bending
1223			δ (O–H) bending asym
1205			CH3 deformation
1161			ν (C–Nazo) δ(CH)
1149	1155	1157	δ (CH3) rocking, methoxy
1107			aromatic CH bending in-plane
		1078	ρ (CH3) rocking
1020	1028	1024	ring breathing
987			δ (C–N=N) out of plane bending (II)
868			ring breathing and stretching C–O
835			γ(C–O)ring out of ring plane OH bending
748			γ(N–C–C–O)oop resonance form of Amide V