Problem 2

C₇H₁₄O
Rule 2, omit O, gives C₇H₁₄
7 - 14/2 + 1 = 1 degree of unsaturation.
Look for 1 pi bond or aliphatic ring.

The band at 1718 indicates a carbonyl, probably a 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.

Note that D and E are chemically similar enough that their peaks overlap.