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

[Oldor]

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]

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).

 

[JDanielK]

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)?

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?

 

[TeethWhitener]

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?

 

[JDanielK]

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)

 

[sjb-2812]

Peaks, or environments? Each of the protons is different in malic acid, so feasibly you could see 6 different environments.

 

[JDanielK]

How would you determine the structure of Malic acid from the NMR above?

 

[sjb-2812]

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.

 

[JDanielK]

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.

 

[TeethWhitener]

How could you integrate this graph?

What do you think integration means?

 

[JDanielK]

What do you think integration means?

The number of protons relevant to the peak.

 

[TeethWhitener]

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.