Answer:
1. Butyraldehyde; 2. but-3-en-1-ol
Explanation:
1. Peak ≥ 160 ppm
The formula C₄H₈O shows that the Index of Hydrogen Deficiency = 1.
It could be caused by either a ring or a double bond.
A peak at ≥ 160 ppm strongly indicates a C=O group, so the rest of the molecule can contain no rings or double bonds.
There are no other heteroatoms, so the compound most be an aldehyde or a ketone.
One compound that meets these criteria is butyraldehyde, CH₃CH₂CH₂CH=O (see Fig. 1.)
2. No rings; all peaks < 160 ppm
If all peaks are < 160 ppm, there can no C=O group.
There is no ring, so there must be a C=C double bond.
There is no other unsaturation, so the O atom must be present as an alcohol or an ether.
One compound that meets these criteria is but-3-en-1-ol, CH₂=CHCH₂CH₂OH (see Fig. 2).
