Problem 7

C₈H₁₄O₃
Rule 2, omit O, gives C₈H₁₄
8 - 14/2 + 1 = 2 degrees of unsaturation.
Look for 2 pi bonds or aliphatic rings, or 1 of each.

The bands at 1745 and 1716 indicate that there are two carbonyls, probably an aliphatic ester and an aliphatic ketone. The bands at 3000-2850 indicate C-H alkane stretches.

This is the structure. See if you can assign the peaks on your own.

Even though A, B, C and D are all 2H peaks, they can be distinguished by chemical shift and splitting. B is outside the normal range for protons next to carbonyls, because it's adjacent to both carbonyls and the combined deshielding is higher than normal.