Problem 19

C₉H₁₃N
Rule 3, omit the N and one H, gives C₉H₁₂
9 - 12/2 + 1 = 4 degrees of unsaturation.
Look for an aromatic ring.

The bands at 3000-2850 indicate C-H alkane stretches. The band at 3028 indicates C-H aromatic stretch; aromatics also show bands in the regions 1600-1585 and 1500-1400 (C-C in-ring stretch), and 900-675 (C-H out-of-plane). The bands in the region 1250-1020 could be due to C-N stretch. The weak, broad banc at about 3500 could be amine N-H stretch or it could be a slight contamination of an impurity (water) in the sample.

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