The starting point is conveniently working out with the "double bond equivalent" from the molecular formula. This shows the presence of one "double bond".

This problem is an exercice in calculating a molecular formula, and "hunting" the missing atom. Compound 1 exhibits "heteronuclear" coupling to either F or P atoms, both common in a wide range of organic and inorganic compounds.

Strong supporting evidence for the stucture could be obtained by looking at the infrared spectra. Those compounds containing a C=O group would show a strong peak at 1650-1750 cm-1.