[McCoy]

I'm stuck somewhere here:
MF=C9H18O3.
Chemical shift(ppm)   multiplicity  Integration
4.1                           t             11.1           
3.6                           s             14.6
3.1                           t             12.0
1.8                           pentet      10.4
1.0                           s              46.2

so this is what I did:the degree of unsat is 1(that can be a double bond or a ring.4.1ppm shouts ester deshielding,So -OCH2-(connected to carbonyl C, so that 1 degree of unsat is a double bond));-;3.6ppm=OCH3;3.1ppm=-CH2-that's near electronegative atom(maybe, maybe not);1.8ppm=-CH2-;1.0ppm=(CH3)3C- .Now the problem is that I can't come up with a reasonable structure of this unknown.The one i end up with is So i need your suggestion please.

[frenchy]

How about a symmetric molecule?

CH₃-O-(CH₂)₃-CO-(CH₂)₃-O-CH₃

so you've got 2 esters and a central ketone

[McCoy]

Thank you Frenchy.
Now let's see your suggestion:
1.now we have a ketone and two ethers(not esters)...so with this structure, we can't explain why we have the chemical shifts listed above.
2.The structure has 4 'types' of Hs which has different chemical environment.
I think I have a rough idea of what caused most of chemical shifts but i just can't assign that 3.1ppm thing to any protons!

[frenchy]

sorry I forgot about the last singlet

CH₃-O-(CH₂)₃-CO₂-C-(CH₃)₃

CH3 ether singlet 3.6ppm
CH2 ether triplet 3.1ppm
CH2 middle pentet 1.8ppm
CH2 ester triplet 4.1ppm
t-butyl group ketone singlet 1.0ppm

that should do it