Table 3.

Fourier-transform infrared spectroscopy peak values of Calotropis procera.

No	Peak (wave number cm −1)	Intensity	Bond	Functional group assignment	Remark an assignment
1	3391	Weak broad	O–H	Hydroxyl group	stretching vibrations of O–H bond in alcohols or phenols
2	2917	Strong	C–H	Alkane	C–H Stretching alkanes
3	2849	Strong	C–H	Alkane	C–H Stretching alkanes
4	1736	medium	C=O	Carbonyl	carbonyl of aldehyde or ketone
5	1462	Medium	C=O	Carbonyl group	carbonyl of aldehyde or ketone
6	1378	Medium	C–H	methylene (–CH2–)	bending vibrations of a methylene (–CH2–) group or a substituted aromatic ring,
7	1244	Weak	C–O	C–O stretching	C–O stretching, bond vibrations from ester groups
8	1013	Weak	C–O	C–O stretching	C–O stretching vibrations of esters, alcohols, or phenols
11	824	Weak	C–H	Alkane	out-of-plane bending vibrations of C–H bonds in aromatic compounds
12	718	Weak	C–H	Methylene	-(CH2)n- Rocking