The presence of peaks at 1734 cm^-1 and 1640 cm^-1 on an infrared spectrum suggests that the compound contains a carbonyl functional group C=O . The peak at 1734 cm^-1 is characteristic of a carbonyl group in an ester, while the peak at 1640 cm^-1 could be due to a C=C double bond or a C=O bond in an amide or a conjugated carbonyl group. However, since the peak at 1734 cm^-1 is more indicative of an ester, it is likely that the functional group present in the sample compound is an ester carbonyl group R-COOR' .