[Violagirl]

Hi so I am having a hard time trying to figure out how to calculate J values and Integration Areas. I was given a spectrum of the compound that I am working with and above each of the peaks, there are ppm energy levels. For example, I have a doublet for one part of the compound and above the peaks are energy level readings that say 7.301 and 7.259. To find the J value and Integration value for this part, would I be able to use this information? I know that I have to also incorporate the level of NMR too which was a 200 MHz spectrometer. The spectrum was done using a CDCl3 solvent. Any help wuld be greatly appreciated.

[YellowLemon]

Hi so I am having a hard time trying to figure out how to calculate J values and Integration Areas. I was given a spectrum of the compound that I am working with and above each of the peaks, there are ppm energy levels. For example, I have a doublet for one part of the compound and above the peaks are energy level readings that say 7.301 and 7.259. To find the J value and Integration value for this part, would I be able to use this information? I know that I have to also incorporate the level of NMR too which was a 200 MHz spectrometer. The spectrum was done using a CDCl3 solvent. Any help wuld be greatly appreciated.

Just think about what they are telling you. 1ppm = 200Hz ; (1*10^-6 * 200*10^6). So go ahead and subtract 7,259 from 7,301 and multiply it with 200. You should come up with 8,4Hz as your answer.

Edit: You can't calculate accurate relative integralvalues with the information you have given, are you sure that there are'nt any lines in the spectra that are giving you that information? I guess that you could calculate it by hand, but the result will most probably be poor...

[Violagirl]

Well they want us to find the chemical shift of each H and I think that there's a way to do it with each surronding compound but can't figure it out. Otherwise for integration if you have more then one peak with different energy levels, can you add them together and then divide the number of H's to figure it out for that one area?

[Nosterius]

Hi Violagirl,

Coupling constants

When you have peak multiplicity (such as doublets and triplets), this is due to a neighboring atom coupling with your proton. Most often, it is due to another hydrogen atom in the vicinity. By determining coupling constants of your protons in your system, you will be able to figure which protons are near each other.

For exemple, if you have a doublet with a J value of 8.4Hz, you should be able to find another set of peaks with a multiplicity of 8.4Hz, meaning that these protons are near each other. This will give you a set of clues about the structure of your molecule.

Integration

If you have multiple peaks in an NMR spectra, the integration gives you a ratio between those peaks.

For exemple, if a peak integrates for 2 and a second for 3, it can also mean you have 4 hydrogen atoms of one type, and 6 of another type. However, if they did not give you the molecular formula, it is more than probable that these integration will be right on.

In the early days of NMR spectroscopy, integration ratio was obtained by cutting and weighing the paper on which the spectra was printed on. I heard that this was a fairly acurate method...

I hope this helps

[fledarmus]

I am surprised that you would receive an NMR that didn't have integration. Integration is something that is calculated from the shape and size of the peak, not from its chemical shift (which I assume is what you mean by energy level).

If there are no integration lines on the spectra, are there numbers attached to brackets below the baseline? That is another way integration is sometimes displayed.

If all you are looking for is the integration of peaks in a multiplet (for example, triplets integrating to 1:2:1 or quartets to 1:3:3:1), you can approximate by peak height.

[helenn]

As fledarmus said there should be integral lines on the spectrum which you need to measure with a ruler from the bottom to top between the horizontal lines, or there will be integration values under each peak. Then you will have the ratio of the different protons in your compound.

The chemical shift for each proton is the average of the multiplet making up the peak, for example for a triplet take the shift in ppm of the tall middle peak, for a doublet add together the shift for each peak of the doublet and divide by 2 to get the mean.