Table 4 Assignment of major functional groups and chemical bonds identified in the FTIR spectra of the oil samples¹⁰.

3300–3450

O–H stretch (carboxylic acid or Alcohol)

3000–3100

C–H stretch in aromatic

2955–2975

CH3 asymmetric

2910–2940

CH2 symmetric (Alkane)

2800–2860

CH2 asymmetric stretch (Alkane)

2720–2735

HC = O (carboxylic acid)

1904–1910

overtones, weak(aromatic)

1580–1630

C = C stretch (in-ring) aromatic

1440–1485

C–H bend or scissoring

1330–1385

C–H rock, methyl (Alkane)

1150–1200

C–O stretch (Alcohol or Esters or carboxylic acid)

1000–1050

C–O stretch (Alcohol or Esters)

850–890

C–H “oop” (Aromatic)

780–820

C-H (aromatic)

710–760

C–H rock, methyl, seen only in long chain alkanes