Question

In an 1H NMR spectrum using CDCl3, you observe a broad peak at 1.5ppm that is...

In an 1H NMR spectrum using CDCl3, you observe a broad peak at 1.5ppm that is not related to your product and integrates for 2.6 Hs relative to a methyl group. What could be responsible for this peak and what might this indicate about your sample?

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Answer #1

The broad peak obtained at 1.5 ppm in 1H NMR spectrum using CDCl3 is due to the water present in the NMR tube. The source of this water can be moisture present in the sample or moisture present in the CDCl3 solvent.

The amount of moisture is variable; therefore integration of this peak at 1.5 ppm is not fixed. Integration increases with increase in water concentration and decreases with decrease in water concentration in NMR sample.

In the given sample if increasing the sample concentration increases the integration of moisture peak, then it can be concluded that sample contains water. However, if the integration remains same (2.6H) even after increasing sample concentration, then it can be concluded that the source of water is NMR solvent (CDCl3).

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