Interpretation of IR, MS, NMR and CNMR Spectra
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StoffFaser
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Interpretation of IR, MS, NMR and CNMR Spectra


Dear Community!

Thank you for welcoming me. My concern is that I need help with the interpretation of 4 different spectra of one organic compound!

I am currently hearing udemy courses additionally to understand the topic better.
I have data for of Mass Spectrum, Infrared Spectrum and two plots of NMR-COSY-Spectra with one 13C-NMR-Signal.



Introducingly I can tell, Mass Spectrum is giving the tallest Peak at 311, most likely the Base Peak (my interpretation) and a smaller peak further right (highest m/z values) at 346 - i'd say it is the molecular ion.

I looked for these mol masses at the nist database, but neither for 311 nor 346 I did find a matching Mass Spectrum for these weights. Do you guys have another database? I think Nist is already very very good, but its baffling me i can't find my compound there. Maybe it's not that easy.

Another but less likely interpretation is: 311 is the molecular ion and 346 is just the isotope of it. But i think with a peak of 30 on the y-axis the abundance and the difference of 35 m/z between 346 and 311 are too high.

The best match up was made by Oryzalin https://webbook.nist.gov/cgi/cbook.cgi?ID=C19044883&Units=SI&Mask=80.

Unfortunatly the match was only acceptable with the IR-Spectrum (not a perfect match though)
A very strong and narrow IR-Peak (~80% absorption) slightly left to the Fingerprint region at 1491 might be a C-H bending. 2 smaller peaks at 3073 very solely of maybe 5% absorption
The fingerprint region below 1400 is not interpretated by me yet, though there are 2 groups of stronger peaks. These 3 charateristics match very well with Oryzalin, but as I said before, not perfectly.

The Mass Spectrum of Oryzalin did not match up very well with the given compound.


NMR was not yet analyzed by me, but i will continue there now.

____________________________________

My questions to you:

1) Do these Spectra have to match up very very perfectly?

2) Is it possible that my compound is very similar to Oryzalin?

3a) Is it feasible to try to identify the compound by comparing the possible fragments from MS-Data with the nist-database? My fragments from 346 m/z are 35, 71, 111, 147, 181, 226 m/z respectively.

3b1) NIST shows plenty of possible molecule fragments when looking for their molecular weight (https://webbook.nist.gov/chemistry/mw-ser/), but I did not try to puzzle these suggested fragments together. Can this be a rewarding try? My time is limited until 28th of August...

3b2) I have learned that Bromine and Chlorine for example detach during the fragmentation process in the mass spectrometer due to weaker bonding force between C-Br and C-Cl than between C-C.
The presence of Br or Cl in the compound would produce peaks or undetected fragments of 122, 124, 43, 78 and 80. All of which are not part of my spectrum. Therefore, the fragments as well as the compounds cannot have Cl and Br, right? So in a procedure of exclusion I can decrease the amount of possible molecules from several hundreds by excluding Chlorine and Bromine in the beginning, can't I?

3b3) If this procedure of exclusion is valid, I might also say that other chemicals like Ketones, Ethers and Esters, Alcoholes are also impossible since my IR-Spectrum is very "clean". Can I exclude these aswell?

3b4) List of what I can exclude right now:
Alkane, Alkene, Alkyne, Alcholes, Carboxyl Acids, Esters, Ethers, Ketones, Amines, Aldehydes
Because my IR-Spectra is too "clean"
Bromine and Chlorine because MS-Peaks don't match.

4) Do you know supplementary databases besides NIST?

5) Do you have any clues how I can go on with the interpretations and information i already gathered? This is the first time I do spectral analysis so help is very welcome, can't say that too often, haha!

This is it for now. I will continue with NMR now and hope you can help me a bit! Right now, I have nobody to discuss this topic with so it would be super helpful if you join the discussion! Smile

Cheers,
StoffFaser


Last edited by StoffFaser on Thu Aug 20, 2020 7:43 am; edited 3 times in total
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StoffFaser
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The C-Circle of Oryzalin has a molecular weight of 72 With 6C and a hypothetic aromatic circle with C6H6 has a m-weight of 78.

both do not match up with my fragments. The fragments of 346 that come closest to this weight is 71, though with the lowest abundance.

I guess it is not possible to sumplement the any C from the C-Circle with another Atom like S, N or O to fit the 71 right?
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StoffFaser
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What might be confusing:

I said the fragments of 346 molecular ions are
35, 71, 111, 147, 181, 226

these come from the difference between the molecular ion and the other MS-peaks namely 120, 165, 199, 235, 275, 311 (base peak) and of course 346 farest right (m. ion)
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