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Chapter 14: Q73P (page 527)

The 1 H NMR spectrum of N,N-dimethylformamide shows three singlets at 2.9, 3.0, and 8.0 ppm. Explain why the two\(C{H_3}\)groups are not equivalent to each other, thus giving rise to two NMR signals.

Short Answer

Expert verified

The number of signals in a PMR spectrum is equal to the number of kinds of protons present in the molecule.The splitting of the NMR signal is caused by spin-spin coupling.

Step by step solution

01

Step 1: \(^{\bf{1}}{\bf{H}}\) NMR

The number of signals in a PMR spectrum is equal to the number of kinds of protons present in the molecule.The splitting of the NMR signal is caused by spin-spin coupling.

02

Non-equivalent proton in NMR

The structure for N,N-dimethylformamide places the two\(C{H_3}\)groups in different environments and different chemical shifts. One\(C{H_3}\)group is cis to the O atom, and one is cis to the H atom.

This gives rise to two different absorptions for the\(C{H_3}\)groups.

It should be noted that spin-spin splitting is observed only between non-equivalent neighboring protons.

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