H NMR Spectrum - Molecular Structure

[edimeo25]

Homework Statement

Give the structure of C8H8O3.

Homework Equations

IR tells us that there is an OH group and a C=O group
Degree of saturation = 5 --> Benzene ring + C=O

H NMR spectrum shows:
Peak at ~7.8ppm integrating for 1H and is a doublet
Peak at ~7.45ppm integrating for 1H and is a triplet
Peak at ~7ppm integrating for 1H and is a doublet
Peak at ~6.85ppm integrating for 1H and is a triplet
Peak at ~3.5ppm integrating for 4H and is a singlet

The Attempt at a Solution

It's hard to show my attempt at a solution, but I believe it will be a meta-disubstituted benzene ring. I just can't figure out how to insert the 3rd oxygen atom and how exactly you can have 4 chemically identical hydrogens with no neighboring hydrogens in this type of molecule. The 3 peaks between 7.8 and 7ppm I believe account for the neighboring hydrogrens of the benzene ring if its substituents are in the meta orientation.

Any help would be greatly appreciated. Thanks for your time.

 

[chemisttree]

Since you have an OH by IR given to you in this problem, start there. In NMR, the OH group usually shows up as a broad hump or a singlet depending on concentration and solvent. You only have one signal that you identified as a singlet at ~3.5 ppm so that's got to be it, however; it integrates to four protons. That's a problem...
Is it possible that you have two coincident singlets present that integerate to 4 protons? If so, what other functional group has an absorbance of ~3.5 ppm? What solvent is used in the NMR?

 

[Blueshift5]

Based on the given information, the structure of C8H8O3 can be determined as meta-hydroxybenzaldehyde. This is supported by the IR spectrum, which shows an OH group and a C=O group, and the H NMR spectrum, which has peaks at ~7.8ppm, ~7.45ppm, and ~7ppm, indicating a meta-disubstituted benzene ring. The peak at ~3.5ppm integrating for 4H and is a singlet can be attributed to the four chemically identical hydrogens of the aldehyde group. The third oxygen atom can be placed on the benzene ring, making it a meta-hydroxybenzaldehyde.