why we have to normalize the proton NMR areas to determine the mole % oa a compound in a mixture?
To determine the mole percentage of a compound in a mixture using proton Nuclear Magnetic Resonance (NMR), we need to normalize the NMR areas. This normalization is necessary because the NMR spectra are influenced by the concentration and number of protons in each compound.
The NMR signal or peak area is directly proportional to the number of protons that contribute to that particular signal. However, the absolute peak areas in NMR spectra can be influenced by various factors, such as the concentration of the sample and the instrument sensitivity.
To eliminate these factors and accurately determine the mole percentage, we normalize the NMR areas. Normalization is the process of dividing the area of a specific peak by the total area of all the peaks in the spectrum. This allows us to account for differences in sample concentration and instrument sensitivity.
Here's how you can perform the normalization and calculate the mole percentage:
1. Obtain the NMR spectrum of the mixture containing the compound of interest.
2. Identify the peak corresponding to the compound you want to determine the mole percentage.
3. Measure the integration value (peak area) of this peak.
4. Measure the integration values of all other peaks in the spectrum.
5. Add up all the integration values to find the total area of all peaks.
6. Normalize the integration value of the compound peak by dividing it by the total area.
Normalized value = Peak area of compound of interest / Total area of all peaks
7. Multiply the normalized value by 100 to obtain the mole percentage as a percentage.
By normalizing the NMR areas, we can accurately determine the relative amount of a compound in a mixture, taking into account the various factors that may affect the NMR signals.