Problem 11

C₈H₈O₂
Rule 2, omit O, gives C₈H₈
8 - 8/2 + 1 = 5 degrees of unsaturation.
Look for an aromatic ring, plus another pi bond or aliphatic ring.

The band at 1689 indicates a carbonyl, probably an acid. The broad dip at 2924 indicates the OH group of the acid. The band at 1589 indicates an aromatic ring.

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

You are not expected to tell the aromatic Hs apart from each other, but you should be able to tell that the ring is not para-substituted.