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Please sketch out the theoretical 1H-NMR spectrum for your product. Label the scale, assign...

Question:

Please sketch out the theoretical {eq}^1 {/eq}H-NMR spectrum for your product. Label the scale, assign shifts, multiplicity, and integration.

Proton NMR

The aromatic region of a proton NMR is often difficult to interpret since the coupling of protons can be complex and the signals often overlap. One way of getting a better understanding of the aromatic region is with a Carbon NMR. Since all signals on this spectra is singlets, and the chemical shifts are more spread out, it is sometimes easier to interpret. The combination of information obtained by a proton and carbon NMR therefore can help with the determination of a structure, especially with a substituted benzene ring

Answer and Explanation:

The product of this oxidation reaction is benzaldehyde.

The image below indicates the structure and the theoretical NMR.

Benzaldehyde

The proton associated with the aldehyde will be down field at approximately 10 ppm. This will be a singlet.

The other 2 protons next to the aldehyde group will form a triplet (labelled as b). This is caused by the big coupling with protons c and a small coupling with proton d. Since it is closer to the aldehyde group we can expect it to be move more down field.

For the remaining 3 protons (c and b), we can expect a multiplet since the peaks will most probably overlap. The multiplicity of these protons will also be more complex: Protons will have relative big couplings with protons next to it (ortho couplings) and smaller couplings with the protons 1 carbon removed (meta couplings).


Learn more about this topic:

How to Read NMR Spectra of Organic Compounds
How to Read NMR Spectra of Organic Compounds

from Organic Chemistry: Help & Review

Chapter 2 / Lesson 2
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