Proton spectrum integration

Fig. 8 Proton spectrum of 1 with (below) integration values and (above) numbers of chemically shifted protons in the molecule. The singlet due to the aromatic protons has been set equal to two protons...

The proton spectrum, with integration. This spectrum tells you ... 

The proton-carbon correlation spectrum, which tells you directly which signals in the proton spectrum correspond with which signals in the broad-band decoupled carbon spectrum. This information, together with the integration values and the multiplicities obtained from APT (or DEPT), is invaluable in putting together the molecular fragments. 

Spectrum 1.3 90 MHz proton spectrum of ethanol with integrals. 

The nmr spectrum shows three kinds of signals corresponding to three kinds of protons. The integral shows these are in the ratio of 2 3 3. From this, we can conclude that they are two different kinds of CH3— groups and a —CH2— group. 

The proton spectrum consists of classical first-order multiplets. From left to right, the multiplicities and integrations are triplet (2), singlet (1), doublets of triplet (2), triplet (1), which yields six hydrogen atoms. The 13C/DEPT spectra provide four carbon atoms that read from left to right C, CH, CH2, CH2. This discrepancy implies that one of the protons is bonded to a heteroatom. The OH proton at 2.68 ppm in the H spectrum accounts for the difference in proton count between the H spectrum and the l3C/DEPT spectrum. 

To avoid instability, keep the sample out of light by covering it completely with aluminum foil when not in the magnet. To avoid thermal instability, do not heat the sample above ambient conditions. Keep the sample capped or sealed to minimize exposure to air. Dissolve the sample in solvent immediately before running the NMR experiments to evaluate its stability in solvent. Obtain a standard proton spectrum immediately after making up the sample as a stability reference. Obtain a second proton spectrum after the final NMR experiment to verify that sample integrity was maintained. Obtain another proton spectrum if any additional experiments are subsequently required. 

It Is possible to obtain quantitative data from the NMR spectrum Integral. Referring to Fig. 4, If the Integral of peaks designated b Is divided by 8 (the number of protons In the MDI contributing to this resonance), we have a number for the relative amount of MDI present, that la. 

However, we must cope with an apparent discrepancy The DEPT spectrum shows one CH, four CH2, and one CH3 groups whereas the integrated proton spectrum apparently shows three CH, three CH2, and... 

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