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Organic Chemistry - 1H and 13C NMR Problem. HELP!

  1. Sep 8, 2012 #1
    1. The problem statement, all variables and given/known data
    Determine the structure of the compound given the information below


    2. Relevant equations
    Molecular Formula:
    C8H6O4

    1H NMR:
    1.57 (d, J=8.66 Hz, 1 H) 1.77 (d, J=8.66 Hz, 1 H) 3.51 (d, J=3.00 Hz, 1 H) 3.51 (d, J=3.00 Hz, 1 H) 3.60 (sc,J=7.56, 3.00 Hz, 1 H) 3.60 (sc, J=7.56, 3.00 Hz, 1 H) 6.31 (s, 2 H)


    13C NMR:
    46.10 (s, 1 C) 46.10 (s, 1 C) 47.20 (s, 1 C) 47.20 (s, 1 C) 52.80 (s, 1 C) 135.60 (s, 1 C) 135.60 (s, 1 C) 171.50 (s, 1 C) 171.50 (s, 1 C)


    3. The attempt at a solution
    So, here's what I've been able to figure out thus far:

    I decided to first find the degree of unsaturation in this molecule, which comes out as 6.

    From that, my first thought was that I could get 4 degrees from a benzene ring, and 2 degrees from 2 carbonyls (somehow) attached to the ring.

    Based on the highest signal of the carbon NMR, I know that one of the carbons is going to be some sort of R(CO)X derivative, and thus I won't have any hydroxyls within my final structure.

    Given the highest signal on my proton NMR, I figured that there were only going to be 2 symmetrical hydrogen atoms (somewhere) on my ring. Either that, or the remote possibility of putting a CH2 right between two esters. There's also the possibility of having a double end, with one end being attached directly to two esters.

    My biggest problem comes from the fact that I have two proton signals in the 1.57-1.77 range, and the 3.51-3.60 range. This tells me that I have some carbons NOT involved in the ring, but at the same time I have carbons that are adjacent to either side of the ester groups.

    I've tried designing a few structures, but they always keep falling short of either the molecular formula, the integration of each shift, or the group I tried adding doesn't match with the observed deshielding.


    What are your thoughts, guys? All feedback is greatly appreciated!
     
    Last edited: Sep 8, 2012
  2. jcsd
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