Table 2.

FT-IR bands of NLP absorption corresponding to chemical bonds.

Sl. No	Absorption Potential (cm−1)	Functional groups	Band strength	Probable peak range (cm−1)	Related chemical fractions	References
1	3338.46	O–H O–H -N-H >N–H	Strong, broad	3200–3570 3200–3400 3325–3345 3310–3360	Alcohol Polymeric compound Aliphatic primary amine Aliphatic secondary amine	[59]
2	2916.32	C–H, >CH2	Weak, sharper	2915–2935	Saturated aliphatic alkene (Methylene)	[60]
3	2848.49	C–H, >CH2	Weak, sharper	2845–2865	Saturated aliphatic alkene (Methylene)	[61]
4	1629.16	C C R2C O, –C(=O)–N O -C N–N N-R-N N–R	Medium, sharp	1600–1700 1620–1680 1620–1640 1600–1650 1590–1690 1575–1630	Alkenes Olefinic alkenes (Alkenyl group) Organic nitrates Conjugated ketone (Quinone) Open-chain imino group Open-chain azo group	[62,63]
5	1420.88	v-C-H R–COOH or R–CO₂H	Weak, in plane stretch	1410–1420 1300–1420 1200–1600	Olefinic alkenes Carboxylic acid salt (Carboxylate) Carboxylic acid, Saturated aliphatic ester	[64,65]
6	1317.49	C–N C–OH/Ph-OH P O R–SO2-O-R, S O	Weak	1250–1360 1310–1410 1250–1350 1300–1335	Aromatic primary/secondary/tertiary amines Phenol or tertiary alcohol bend Organic phosphates Dialkyl/aryl sulfonates (esters)	[66]
7	1247.72	Aryl-O-CH2 Aryl-O-CH3	Weak	1230–1270 ∼1250	Aromatic ethers Aromatic ethers (Epoxy/oxirane ring)	[67,68]
8	1158.34	C–N C–N R–S(=O), S O	Weak, in plane stretch	1130–1190 1150–1210 1100–1200	Aliphatic secondary amine Aliphatic tertiary amine Sulfonates	[69,70]
9	1101.68	C–H C–F	Weak	950–1225 1000–1150	Aromatic ring (aryl group) Aliphatic fluoro compound (halogenated)	[71,72]
10	1028.27	>CH2 P–O–C N–C–H Si–O–Si	Strong, sharp	925–1055 990–1050 1020–1090 1020–1055	Methylene, cyclohexane ring Aliphatic phosphates Primary amine Organic siloxane	[73,74]
11	898.99	vinyl-C-H, C CH2 C–H	Weak, out of plane stretch	890–915 800–900 600–1000	Olefinic alkene Aromatic 1,3 para/meta distribution Alkyl halides, glycosides	[75,76]
12	812.81	C–H	Weak	800–900 800–890	Aromatic 1,3 para/meta distribution Aromatic ethers (Epoxy/oxirane ring)	[77,78]
13	715.45	C–Cl R–S–C(=O)−R	Weak, out of plane stretch	700–800 670–715	Aliphatic chloro compound (halogenated) Aryl thio-esters (C-5)	[79,80]
14	582.99	C–S/R–S–S−R′	Weak stretch	570–705	Disulfides	[81,82]