Anonymous asked in Science & MathematicsChemistry · 1 year ago

Chemistry question ?


What molecule best fits the diagram 

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2 Answers

  • 1 year ago
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    This "diagram" is called a 13C-NMR spectrum. It is always important to name "diagrams" and other data by the correct name.

    Now on to the question. You show 2 possible answers (although there is another possible solution, which is not completely shown on the picture). The difference is the methyl group attached to the phenyl ring of both molecules. [a] shows the ethyl p-methylbenzoate, and [b] shows ethyl o-methylbenzoate. 

    If you would look solely at the phenyl ring with either ortho (1,2) or para (1,4) substituents, you see that for the ortho substituted phenyl ring, there are 6 carbon atoms which all have different electronic environments.This will result in 6 different carbon peaks.

    For a para substituted phenyl ring you have a symmetric structure. This means that you have 2 sets of 2 carbons, which have identical electronic properties, plus the carbons containing the substituents. A para-substituted phenyl structure will therefore show 2 peaks with double peak integration in the aromatic region (~65-85 ppm) of the NMR-spectrum, plus 2 remaining aromatic carbon signals. 

    If you look at this spectrum you see 2 singlets and 2 'doublets' with double integration, meaning that this molecule is likely ethyl p-methylbenzoate, so answer A.

    I hope you understand the way you tackle these problems and analyze these NMR-spectra!

  • 1 year ago

    Interesting diagram.

    What is the question?

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