How to find integrated peaks on NMR graphs

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In summary, the conversation discusses interpreting NMR graphs in Modern Analytical Chemistry. The speaker is struggling to understand how to find the integrated peaks and has looked online for help. The response explains that the integration begins at the point where the deviation from the baseline into the peak starts, or at the midpoint between adjacent peaks if they are not baseline resolved. However, this method is not exact but provides a close approximation.
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Hi all,

I am currently self studying a chapter on Modern Analytical Chemistry. One part talks about interpreting NMR graphs and I understand the basic gist of it, however, I don't understand how to find the integrated peaks. I've looked extensively online and I now understand that you have to measure the peaks to find the ratio. BUT, how do you know where to start and stop measuring?

An example is http://www.wfu.edu/~ylwong/chem/nmr/h1/integration.html" , if you were to click on the animated flash explanation, they show how it's done, but I don't understand how they came up with where to start and stop the measurement of the peaks.

Thank you in advance!
 
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If the peaks are baseline resolved, the integration begins where the deviation from the baseline into the peak begins. If peaks are not baseline resolved, a midpoint between adjacent peaks is used. It isn't exact, BTW, but it gets you close.
 

FAQ: How to find integrated peaks on NMR graphs

How do I distinguish between noise and integrated peaks on an NMR graph?

One way to distinguish between noise and integrated peaks on an NMR graph is to look at the intensity of the peaks. Noise will typically have a lower intensity compared to integrated peaks. Additionally, integrated peaks will also have a distinct shape and be consistent with the expected chemical shift of the molecule.

What are some common methods for identifying integrated peaks on NMR graphs?

Some common methods for identifying integrated peaks on NMR graphs include manual integration, computer-assisted integration, and peak picking software. Manual integration involves visually identifying and measuring the area under each peak on the graph. Computer-assisted integration uses mathematical algorithms to analyze the data and identify integrated peaks. Peak picking software is a type of computer-assisted integration that automatically detects and integrates peaks on the graph.

3. How can I determine the number of protons responsible for an integrated peak?

To determine the number of protons responsible for an integrated peak, you can use the formula: number of protons = integration value / integration ratio. The integration value is the area under the peak, and the integration ratio is the ratio of the peak area to the area of a reference peak (usually the solvent peak).

4. What are some common causes of inaccurate integration on NMR graphs?

Some common causes of inaccurate integration on NMR graphs include noise or interference from other peaks, baseline distortion, and incorrect calibration of the instrument. It is important to carefully examine the graph and make any necessary adjustments or corrections to ensure accurate integration.

5. Can I use integrated peaks to determine the structure of a molecule?

While integrated peaks can provide valuable information about the number of protons in a molecule, they cannot be solely relied upon to determine the complete structure of a molecule. Other techniques, such as 2D NMR experiments, are necessary to fully elucidate the structure of a molecule.

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