The absorbance at 1710 cm is the sum of the absorbance of toluene and OA and therefore the absorbance of OA can be calculated by subtracting the absorbance of toluene at 1710 cm in (Fig. 2.) However, this was unnecessary, owing to the usage of toluene for the background spectrum. (Fig. 3) a displays the FTIR spectra of OA in toluene in the 1780–1650 cm region.