1H NMR: Unsymmetric Peak Multiplicity and J Values

In summary, the conversation discusses the complexity of peak splittings in the aromatic region of the spectrum in proton NMR. Aromatic protons can couple with multiple non-equivalent protons, causing distortion and splitting of peaks. The conversation also suggests looking at splitting diagrams for further understanding and asks for pictures of the spectra for analysis.
  • #1
Organic_Student_2020
1
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Homework Statement
How to find multiplicity and J values for non symmetric 1H NMR spectra?
Relevant Equations
I have tried to figured this out but I can't, I need help on how to find the multiplicity of some of these arrangements of peaks. For example, there is one that looks like (from left to right), a doublet, 2 triplets, and then another doublet. I will Attach crude drawings below, but hopefully I can just get an answer on how to do this exercise.
The peaks all look unfamiliar, no symmetry, or very little, and they all integrate to a small number of hydrogen while being surrounded by a large number.

Here are the images.1.)
NMR Multiplets 1.jpg


2.)
NMR Multiplets 2.jpg


3.)
NMR Multiplets 3.jpg


4.)
NMR Multiplets 5.jpg


5.)
NMR Multiplets 6.jpg


Thanks for any explanations. I don't expect anyone to do it for me, I just have no other resources to figure this out.
 

Attachments

  • NMR Multiplets 4.jpg
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  • #2
Without knowing exactly where these appear in your spectrum, it's tough to say, but I'm guessing these are in the aromatic region of the spectrum (between about 7 and 10 ppm). The aromatic region of proton NMR spectra can give some very complicated peak splittings. Aromatic protons often couple to multiple non-equivalent protons, and even protons that are further than nearest neighboring carbons, which distorts and splits peaks further than what you normally see in the aliphatic region of the spectrum. Here's a link that might help:
https://chem.libretexts.org/Bookshe...Diagrams_Explain_the_Multiplicity_of_a_Signal
 
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Likes etotheipi
  • #3
can you post pictures of the spectra? It is difficult to do any analysis without knowing the exact shape of the peaks.
 

1. What is 1H NMR?

1H NMR (proton nuclear magnetic resonance) is a spectroscopic technique used to study the chemical structure and composition of molecules by analyzing the behavior of hydrogen atoms in a magnetic field.

2. What is unsymmetric peak multiplicity in 1H NMR?

Unsymmetric peak multiplicity refers to the splitting of NMR peaks into different sub-peaks due to the presence of neighboring atoms with different chemical environments. This results in a more complex NMR spectrum with multiple peaks instead of a single peak.

3. How is unsymmetric peak multiplicity related to J values?

J values, also known as coupling constants, are a measure of the strength of the magnetic interaction between neighboring atoms in a molecule. In 1H NMR, J values determine the splitting of NMR peaks, resulting in unsymmetric peak multiplicity.

4. What factors can affect J values and unsymmetric peak multiplicity in 1H NMR?

J values and unsymmetric peak multiplicity can be influenced by a variety of factors, such as the strength of the magnetic field, the type of solvent used, the temperature, and the chemical structure of the molecule being studied.

5. How can the information obtained from unsymmetric peak multiplicity and J values be used in chemical analysis?

The analysis of unsymmetric peak multiplicity and J values in 1H NMR can provide valuable information about the connectivity and stereochemistry of a molecule, as well as its functional groups and overall structure. This information can be used in various fields, including organic chemistry, biochemistry, and pharmaceutical research.

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