Organic Chemistry IR and NMR problem solving

In summary, the student attempted to solve the homework using the NMR data and their hypothesis, but they ran into issues with asymmetry and the data being bad.
  • #1
montoyas7940
364
21
NMR.png

Homework Statement


I am trying to help my daughter determine the structure of this carbon compound. It has seven carbons, 14 hydrogens and one oxygen. The oxygen must be in a ketone group. Also each carbon is different (as indicated by the carbon 13 NMR).

Homework Equations




The Attempt at a Solution


We think that the correct interpertation of the NMR shown is that there are 4 hydrogens with 3 neighboring hydrogens, 2 hydrogens with 4 nieghboring hydrogens, 2 hydrogens with 5 neighboring hydrogens, 3 hydrogens with 2 neighboring hydrogens and 3 hydrogens with 2 neighboring hydrogens. [/B]

Are we correct so far? Any suggestions?
 

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  • #2
Looks reasonable. What do the NMR shifts tell you about relative distances from the carbonyl functional group?
 
  • #3
Bystander said:
Looks reasonable. What do the NMR shifts tell you about relative distances from the carbonyl functional group?
The 4 hydrogens will be closest to the carbonyl and the 3 hydrogens will be farthest from the carbonyl. And one of the groups of 3 hydrogens will be closer than the other group of three hydrogens.
 
  • #4
montoyas7940 said:
group of three hydrogens.
Might as well call these two methyl groups.
Next, the four most shifted hydrogens: possibility of superposition of triplets?
 
  • #5
By triplets do you mean the four most shifted hydrogens having three (hydrogen) neighbors? That is the premise we have been working with but we must be missing something obvious.
 
  • #6
I was wondering if the "quartet" might actually be a pair of triplets sitting almost on top of each other. Haven't got Silverstein and Basler handy, and I'm winging it right now on that part. If it is, the whole thing becomes "trivial." Hah, hah --- sure.
 
  • #7
Arrgh! Taking a break. Then we will play with it some more. Thanks for the suggestion.
 
  • #8
Asymmetry baffles me.
 
  • #9
As it turns out, the data is bad.

Scratch the 4 hydrogens with 3 neighbors. So it becomes 7 carbon atoms in a line with the third having a double bond with oxygen.

Thanks for looking at it!
 
  • #10
montoyas7940 said:
As it turns out, the data is bad.
And this was a teaching exercise for your daughter? I would demand my money back.
 
  • #11
Bystander said:
I would demand my money back.

Full scholarship...

I guess you really do get what you pay for.
 

1. What is the purpose of using IR and NMR in organic chemistry?

The purpose of using IR (Infrared) and NMR (Nuclear Magnetic Resonance) in organic chemistry is to identify and analyze the functional groups and molecular structures present in a compound. This information can help determine the chemical properties and behavior of the compound.

2. How does IR and NMR differ in their use in organic chemistry?

IR spectroscopy measures the vibrations of the molecular bonds in a compound, while NMR spectroscopy measures the magnetic properties of the nuclei in a compound. This means that IR is useful for identifying functional groups, while NMR is useful for determining the connectivity and arrangement of atoms within a molecule.

3. What type of information can be obtained from an IR spectrum?

An IR spectrum provides information about the types of chemical bonds present in a compound, as well as the functional groups that are present. It can also give insight into the molecular structure, symmetry, and polarity of a compound.

4. How do you approach problem solving using IR and NMR in organic chemistry?

The first step in solving an IR or NMR problem is to carefully analyze the given spectrum and identify any characteristic peaks or patterns. Next, compare these peaks to known values in reference tables to determine the functional groups or molecular structures present. Finally, use all available information to piece together the complete structure of the compound.

5. What are some common challenges when using IR and NMR in organic chemistry problem solving?

One common challenge is the presence of overlapping peaks in the spectrum, which can make it difficult to accurately identify and interpret the data. Another challenge is the need for a deep understanding of organic chemistry principles and functional group properties in order to effectively use IR and NMR data for problem solving.

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