H NMR questions help

Just this:

I think your right for example 3

example 4 - could it be:

CH3CH2COOCH2CH3

this would give the 2 triplets and 2 quartets, but I have not looked at chemical shifts only the splitting patterns!!

Let's consider the first molecule, C4H8O2. If the molecule was fully saturated it would have 10 hydrogens, yet this one has only 8. This means that there is a double bond in this molecule. Most likely, it is the carbonyl. Let's consider all the peaks, from right to left. First peak is at 4.12ppm. The chemical shift indicates carbon attached to oxygen. Since this is a quartet, n+1 rule tells us that this carbon is also attached to CH3. I am assuming you have done integration, so we know that this peak at 4.12 ppm represents 2 hydrogens. So, for peak at 4.12ppm we have the following fragment: O-CH2-CH3. Next peak is at 2.00 ppm and it is a singlet. The chemical shift indicates that this carbon is next to the carbonyl. Integration tells us that this peak represents 3 hydrogens. Therefore, the fragment is: CH3-C=O. Last peak is a triples at 1.26 pm that integrates to 3 hydrogens. This is CH3 connected to CH2. Here is the full structure: CH3-C(O)-O-CH2-CH3