Understand Splitting Patterns for NMR Molecules

In summary, this individual is struggling to determine splitting patterns for molecules and is unsure if they are correct. They also have questions about how to determine which is the farthest down field and what groups have down field resonances in general.
  • #1
katiecool
4
0
I am struggling to understand how to determine splitting patterns for molecules. For example, (see attached) I was trying to determine the splitting pattern for CH2 in the molecule. On the right i believe n is equal to 1 and on the right it is equal to 3, but i am not sure if this is correct. A doublet quartet doesn't make any sense to me and that is what i seem to conclude. The addition of the OH is really throwing me off. Also, on top of that how would i begin to determine which is farthest down field! Any help would be great!
 

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  • #2
I'm sorry you are not generating any responses at the moment. Is there any additional information you can share with us? Any new findings?
 
  • #3
I think that i am miss understanding how to determine which are equivalent hydrogen's. Equivalent hydrogen's act as a group. On both CH3's all the hydrogen's are equivalent. so "n" for both CH3's are equal to one. Thus i think it may be n=4 and n+1=5 so the splitting pattern would be a pentet? Can confirm that i am right?
 
  • #4
You were more right the first time. It may be that the J values are similar so it looks like a quintet, but this is just a resolution thing. As to which is more downfield, what kind of groups have downfield resonances in general?
 
  • #5
I agree, but what i wrote the first time is something i learned outside of my notes. A pentet was something in my notes. So a pentet is possible? and i think that it would be the the part of the molecule with the fewest hydrogens...so CH i think would be the farthest downfield?
 
  • #6
A quintet would be more possible if you were only coupling to a nucleus with spin I=2, it's certainly not impossible.

I agree that the CH would be the most down field, but not because it has the fewest hydrogens. The CH in terminal alkynes for instance resonates at about δ3-4 from memory. Look into the electronic environment of the protons. I can see a similar thread on chemicalforums.com; it may be worth looking there too.
 

1. What is NMR spectroscopy and why is it important in chemistry?

NMR spectroscopy, or nuclear magnetic resonance spectroscopy, is a technique used to analyze the chemical structure of molecules by studying the interactions between atomic nuclei and a strong magnetic field. It is important in chemistry because it allows scientists to identify the types and positions of atoms within a molecule, giving insight into its structure and properties.

2. How does NMR spectroscopy work?

NMR spectroscopy works by applying a strong magnetic field to a sample of molecules, causing the atomic nuclei to align with the field. A radiofrequency pulse is then applied, which causes the nuclei to resonate and emit a signal. By measuring the frequency and intensity of this signal, information about the chemical environment of the nuclei can be obtained.

3. What are splitting patterns in NMR spectra?

Splitting patterns in NMR spectra refer to the splitting or splitting of a signal into multiple peaks. This occurs when the nuclei in a molecule are in slightly different chemical environments, causing them to resonate at slightly different frequencies. The number and arrangement of these peaks can provide information about the neighboring atoms in the molecule.

4. How do you interpret splitting patterns in NMR spectra?

To interpret splitting patterns in NMR spectra, you must first determine the number of unique nuclei in the molecule. This can be done by counting the number of peaks in the spectrum. Then, you can use the n+1 rule to determine the splitting pattern. For example, if a nucleus has n neighboring nuclei, it will produce a signal split into n+1 peaks.

5. What factors can affect the splitting patterns in NMR spectra?

Several factors can affect the splitting patterns in NMR spectra, including the number of neighboring nuclei, the strength of the magnetic field, and the type of nuclei present. Additionally, environmental factors such as temperature and solvent can also impact the splitting patterns. It is important to consider these factors when interpreting NMR spectra to accurately determine the structure of a molecule.

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