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NMR questions set 1 solutions - Practice NMR questions set...

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Practice NMR questions set 1 solutionsGiven the molecular formula and the HNMR shown below, predict the structure of the unknown.(There are two doublets at 7.1 and 6.7, a quartet at 2.6, and a triplet at 1.3)Molecular formula: C8H10OMy thoughts: Using the molecular formula, the degrees of unsaturation calculated is 4. Since wesee 2 sets of peaks in the 6.7-7.1 region, there is most likely a benzene ring present. Thisaccounts for the 4 degrees of unsaturation (3 for double bonds + 1 for ring). Looking at twodoublets at 7.1 and 6.7, there are a total of four benzene ring hydrogens, suggesting that there are2 substituents present on the ring. Also, since there are only 2 peaks instead of 4 for the benzenehydrogens, this suggests that the molecule has a plane of symmetry that allows for only 2benzene hydrogen peaks instead of 4. Looking further down the NMR, there is a wide short peakaround 5.4 (I call them little fatties). This wide short peak is indicative of either an aminehydrogen or alcohol hydrogen. Since the molecular formula has no nitrogen and an oxygen, theremust be an alcohol present on the compound, most likely attached to the benzene ring itself. The2 hydrogen quartet at 2.6 and 3 hydrogen triplet at 1.3 is characterstic of an ethyl group. Sinceone of the peak is at 2.6, more upfield than an alkane usually is, this means that it is attacheddirectly to the benzene ring, deshielding the alkane hydrogens and making it more upfield. Sincewe know that there is a plane of symmetry, the alcohol and ethyl group must be 1-4 to each other.Putting all of this information together, we get the unknown compound

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Term
Spring
Professor
N/A
Tags
Carboxylic acid, Functional group, HNMR

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