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Topic: Structure Elucidation from a H1 NMR Spectrum  (Read 984 times)

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Offline kakarot

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Structure Elucidation from a H1 NMR Spectrum
« on: February 27, 2021, 12:35:00 PM »
https://drive.google.com/file/d/1rb7cLZaDBdaCXUKfFSgJGcZOC6yeUo8Z/view?usp=sharing

Tried embedding image but doesn't appear, so posting link instead which will hopefully work.

I'm struggling with identifying the structure of a molecule, who’s molecular formula is C10H12O3 and has a H1 NMR as shown above. I’ve managed to identify some of the easier characteristic peaks, such as the Peak at 5.14 being characteristic of an OH bond, and the cluster at 7.75 – 7.17 representing an aromatic ring, probably with one chain coming off it, but beyond that I’m stumped as to identifying the peaks and putting the whole thing together. Any help and insight into this would be really appreciated.

Offline AWK

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Re: Structure Elucidation from a H1 NMR Spectrum
« Reply #1 on: February 27, 2021, 12:47:43 PM »
Wrong -OH assignment.
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Offline kakarot

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Re: Structure Elucidation from a H1 NMR Spectrum
« Reply #2 on: February 27, 2021, 01:09:33 PM »
I thought it would have been OH because the deshielding effect increases the chemical shift. Any advice on what it could be instead?

Offline AWK

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Re: Structure Elucidation from a H1 NMR Spectrum
« Reply #3 on: February 27, 2021, 02:35:20 PM »
You have a hint on the spectrum - proton exchanges to deuterium with heavy water.
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Offline Babcock_Hall

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Re: Structure Elucidation from a H1 NMR Spectrum
« Reply #4 on: February 27, 2021, 02:46:59 PM »
The fact that it is broad is also helpful.

Offline kakarot

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Re: Structure Elucidation from a H1 NMR Spectrum
« Reply #5 on: February 28, 2021, 11:20:13 AM »
I’ve figured out why the broad peak at 3.62 ppm represents an OH functional group. But I’m still having real difficulties assigning the other peaks. I’m afraid I may be missing some step which allows me to reduce the complexity of the spectrum to identifiable components. 

Offline Vidya

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Re: Structure Elucidation from a H1 NMR Spectrum
« Reply #6 on: March 01, 2021, 01:15:11 AM »
Quote
who’s molecular formula is C10H12O3
Get the degrees of unsaturation or index of hydrogen
You have correctly identified aromatic ring ...now check if it is monosubstituted or di  or multisubstituted .This information we can take out from the number of signals and their splitting pattern.
Now you know it is alcohol
Other signals are indicating strongly deshielded due to ester
Aromatic ring signals are for 5H and not very deshielded .
I think this is a good amount of information to know the structure.

Offline kakarot

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Re: Structure Elucidation from a H1 NMR Spectrum
« Reply #7 on: March 02, 2021, 05:44:26 PM »
Thanks for all the Help.  :)

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