The third spectrum is attached, for C5H8O2.
With this one I have the biggest problem. I know it's neither an alcohol, nor a carboxylic acid. I analyzed the fragments, which gave me several options, which I don't know how to eliminate:
1. dialdehyle, which would be glutaraldehyde
2. diketone- either 2,3-Pentanedione or Acetylacetone
3. An ester- Acetic acid, 2-propenyl ester or Propanoic acid, ethenyl ester.
Another thing is that I don't know how to approach the 57 and 58 fragments- what are they? what do they hint for?
Many thanks again