Table 6.

The characteristic bands of methylxanthines in FTIR and Raman spectra.

FTIR (cm–1)			Raman (cm–1)
This Study	[38]	Assignment	This Study	[38]	Assignment
Caffeine
481	481	δ a C–N–C	226	225	δ N–C–N
610	611	δ C=C–C	442	444	δ N–C–C
745	743	δ O=C–C	481	488	δ a C–N–C
860	862	δ N=C–H	553	556	δ C-N–CH3
973	973	ν N–CH3	641	645	δ C=C–N
1025	1025	ν a N–CH3	739	745	δ C=C–C
1188	1189	ν CC, ν a CN	799	800	δ N–C–H
1239	1237	ν CN	925	925	ν s N–CH3
1286	1285	ν CN	1019	1020	ν a N–CH3
1549	1548	ν s C=O	1240	1241	ν CN
1598	1600	ν C=C	1282	1288	ν CN
1659	1660	ν a C=O	1326	1331	ν CN
1699	1700	ν C=N	1598	1600	ν C=C
2953	2954	ν CH	1654	1656	ν a C=O
			1696	1700	ν C=N
			2958	2963	ν CH
Theophylline
446	450	δ N–C–C	444	450	δ a C–N–C
504	500	δ a C–N–C	552	550	δ C=C–C
610	615	δ C=C–N	608	610	δ C=C–N
667	670	δ O=C–N	664	660	δ O=C–N
742	744	δ O=C–C	762	760	δ O=C–C
848	850	δ C–N–H	925	920	δ N–C–N
927	925	ν s N–CH3	947	940	ν s N–CH3
979	980	ν a N–CH3	967	970	δ N=C–H
1241	1240	ν CN	1082	1088	ν s C–N
1284	1285	ν CN	1246	1244	ν C–N
1313	1310	ν CN	1284	1280	ν C–N
1567	1556	ν s C=O	1568	1570	ν s C=O
1667	1664	ν a C=O	1609	1613	ν C=C
1718	1710	ν C=N	1662	1663	ν a C=O
			1704	1706	ν C=N
			3121	3120	ν N–H

Vibrations: ν—stretching, δ—deformation, a—asymmetric, s—symmetric.