How many peaks in the NMR spectrum of Malic Acid, without D2O?

Click For Summary

Discussion Overview

The discussion revolves around determining the number of peaks in the NMR spectrum of Malic Acid (HOOC CH2 CH(OH) COOH) when using a solvent other than D2O. Participants explore the implications of different hydrogen environments in the molecule and how these relate to the peaks observed in the NMR spectrum.

Discussion Character

  • Homework-related
  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants suggest that the two -COOH groups will have identical hydrogen environments, leading to one peak for both, while others propose that there may be a total of 4 or 5 peaks depending on the identity of the carboxylic acid groups.
  • A participant asks for an example of the NMR graph and inquires about identifying the number of peaks and their integration.
  • Another participant mentions that databases like SDBS contain spectra of malic acid in aprotic solvents, which align with basic NMR theory.
  • One participant expresses difficulty in analyzing the H-NMR spectrum of Malic Acid and questions how to determine its structure from the graph.
  • There is a suggestion that each proton in malic acid could represent different environments, potentially leading to 6 distinct peaks.
  • Participants discuss the concept of integration in NMR and how it relates to the number of protons corresponding to each peak.

Areas of Agreement / Disagreement

There is no clear consensus on the exact number of peaks in the NMR spectrum of Malic Acid, as participants present differing views on the hydrogen environments. The discussion remains unresolved regarding the specifics of peak identification and integration.

Contextual Notes

Participants express uncertainty about the integration process and how it applies to the specific NMR graph of Malic Acid. The discussion includes references to external databases for spectral data, but limitations in understanding the integration and peak analysis remain.

Who May Find This Useful

This discussion may be useful for students and researchers interested in NMR spectroscopy, particularly those studying organic compounds like Malic Acid and seeking to understand peak analysis and integration in spectral data.

Oldor
Messages
6
Reaction score
0

Homework Statement



How many peaks will there be in the NMR spectrum of Malic Acid, HOOC CH2 CH(OH) COOH, WITHOUT D2O as the solvent (i.e. Hydrogens in Hydroxyl groups WILL have corresponding peaks)?


The Attempt at a Solution



I thought the two -COOH groups will be identical Hydrogen environments, so there would only be one peak for both. There will be one environment with the single H bonded to the Carbon that is also bonded to the OH; one environment with the single H in the -OH bonded to that same Carbon; and one environment with the two H's bonded to the remaining Carbon. A total of 4 peaks without D2O (or 5 if the Carboxylic acid groups are not identical)?
 
Physics news on Phys.org
Oldor said:
I thought the two -COOH groups will be identical Hydrogen environments, so there would only be one peak for both. There will be one environment with the single H bonded to the Carbon that is also bonded to the OH; one environment with the single H in the -OH bonded to that same Carbon; and one environment with the two H's bonded to the remaining Carbon. A total of 4 peaks without D2O (or 5 if the Carboxylic acid groups are not identical)?
This is correct. (the two carboxyl hydrogens are essentially identical).
 
Oldor said:

Homework Statement



How many peaks will there be in the NMR spectrum of Malic Acid, HOOC CH2 CH(OH) COOH, WITHOUT D2O as the solvent (i.e. Hydrogens in Hydroxyl groups WILL have corresponding peaks)?

The Attempt at a Solution



I thought the two -COOH groups will be identical Hydrogen environments, so there would only be one peak for both. There will be one environment with the single H bonded to the Carbon that is also bonded to the OH; one environment with the single H in the -OH bonded to that same Carbon; and one environment with the two H's bonded to the remaining Carbon. A total of 4 peaks without D2O (or 5 if the Carboxylic acid groups are not identical)?
TeethWhitener said:
This is correct. (the two carboxyl hydrogens are essentially identical).
What would be an example of this graph? Could you identify how many peaks and the integration that occurs? If you can, would you explain why it occurs?
 
JDanielK said:
What would be an example of this graph? Could you identify how many peaks and the integration that occurs? If you can, would you explain why it occurs?
There are databases online (SDBS, for example) with the malic acid spectrum in an aprotic solvent like DMSO. The spectrum looks pretty much like what you’d expect from basic NMR theory. Is there anything specific you want to know about the spectrum?
 
TeethWhitener said:
There are databases online (SDBS, for example) with the malic acid spectrum in an aprotic solvent like DMSO. The spectrum looks pretty much like what you’d expect from basic NMR theory. Is there anything specific you want to know about the spectrum?
Thank you for the quick reply! I have an H-NMR of Malic Acid and am having trouble understanding it and cannot analyse it properly. How can I determine the structure of Malic Acid (HOOCCH2CH(OH)COOH) from this graph? Does integration and peak numbers have anything to do with it?. Below is the spectrum of Malic acid. I'm lost when it comes to these graphs. It was sourced from:(http://bmrb.wisc.edu/metabolomics/mol_summary/show_data.php?id=bmse000238&whichTab=1 and http://bmrb.wisc.edu/ftp/pub/bmrb/metabolomics/entry_directories/bmse000238/nmr/set01/spectra/1H.png)
 

Attachments

  • 1H.png
    1H.png
    6.9 KB · Views: 925
Last edited:
Peaks, or environments? Each of the protons is different in malic acid, so feasibly you could see 6 different environments.
 
How would you determine the structure of Malic acid from the NMR above?
 
In short, I probably wouldn't, at least not in isolation. I may have an inkling of how my unknown was made, or other spectral data. Also, in 1H NMR these are usually integrated, which may also give a clue.
 
  • Like
Likes   Reactions: TeethWhitener
Thanks for the answers! I apologise if I seem repetitive, but this stuff genuinely stumps me. How could you integrate this graph? Is it even possible for this to be done on this particular graph? Again I apologise if I'm repetitive, but I need help. Thank you.
 
  • #10
JDanielK said:
How could you integrate this graph?
What do you think integration means?
 
  • #11
TeethWhitener said:
What do you think integration means?
The number of protons relevant to the peak.
 
  • #12
JDanielK said:
The number of protons relevant to the peak.
Do you understand how this number is obtained? There's a reason we use the word "integration." It's the same integration we do in calculus.
 

Similar threads

How many peaks will there be in an NMR spectrum for Malic Acid?
  • · Replies 2 ·
Replies
2
Views
3K
Chemistry Processing a "Raw Spectrum" - A Beginner's Attempt
  • · Replies 17 ·
Replies
17
Views
3K
How Many Stereoisomers Do Hexadecanoic Acid and Oleic Acid Have?
  • · Replies 4 ·
Replies
4
Views
2K
Acidity of lactic acid and propanoic acid
  • · Replies 3 ·
Replies
3
Views
9K
What are the key steps to analyzing an NMR spectrum?
  • · Replies 1 ·
Replies
1
Views
4K
Expert Help with Mass Spectroscopy Homework: IR & NMR Analysis for Molecule B
  • · Replies 2 ·
Replies
2
Views
4K
Chemistry H NMR Spectrum - Molecular Structure
  • · Replies 1 ·
Replies
1
Views
12K
What is the finger print region of an IR spectrum?
  • · Replies 1 ·
Replies
1
Views
4K
NMR: Why do "identical" nuclei not couple with each other?
  • · Replies 3 ·
Replies
3
Views
4K
How many types of protons? (^1 H NMR)
  • · Replies 3 ·
Replies
3
Views
7K