An NMR spectrum of an unknown mixture of CH₂Cl₂ and CHCl3 shows two peaks, at 5.30 ppm for CH₂Cl2, and 7.26 ppm for CHCl3, respectively. The peak at 7.26 ppm integrates for 100 units, while the peak at 5.30 integrates for 50 units. Does this mean that there is twice as much CHCl3 in the mixture? Explain.
In 1H NMR spectra, the integration of a peak is defined by the area covered by that peak. Now the area of any peak depends on the number of equivalent protons.
In the NMR spectra of the mixture of CHCl3 and CH2Cl2, no of equivalent protons is 1 for CHCl3 and 2 for CH2Cl2. So the integration ratio of protons for CHCl3 and CH2Cl2 should be 1:2 if both are taken in same amount.
But according to question, the integration of 100 unit for CHCl3(7.26 ppm) and 50 unit for CH2Cl2(5.30 ppm) respectively. So their ratio of integration is 100:50 = 2:1. It is only possible when amount of CHCl3 will be taken double the amount of CH2Cl2 because at that situation the no of equivalent protons of CHCl3 = 2 x no of equivalent protons of CH2Cl2.
The integration of peak doesn't depend on NMR shift of protons, but depends on the amount of compound taken and its no of equivalent proton.
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