First if you have a data sheet you would compare the four peaks that are denoted by a,b,c and d and see if the number in which the peak falls alligns with a bond type present in the moecule. IR spectroscopy is used quite alot in organc chemistry so using my data sheet I'd assume that;
Peak D, likely represents a C-O bond (found in wavenumer range 1000-1300)
Peak C, likely represents a C-H bending vibrations (with wavenumber range 1400-1500)
Peak B, is likely a C=C bond, (with wavenumber range of 1620-1680
Peak A, is likely a C=O bond, (with wavenumber range of 1680-1750)
From here you could predict some possible molecules that the IR spectrum alligns with ie any molecules that are composed of C-H, C-O, C=O and C=C bonds, like an ester with an unsaturated carbon chain.
