Question

Which of the following compounds with molecular formula C9H1802, is consistent with the following ?H and 13C NMR spectra shown below? 1H NMR 6H, doublet 6H, triplet 4H, pentet 1H, septet 1H, pentet . 13C NMR 180.160.140 120 100 80 60 40 20 PPM a) b)

Answer 1

Based on 13C-NMR:

one carbon (at about 180) is present as C=O.

And one peak between 50-100 ppm implies, one saturated carbon is next to Oxygen, like CH2O or CH3O.

Rest all carbons are at less than 50 ppm meaning they are saturated carbons like CH3, CH2 or CH.

Based on 1H-NMR

The maximum deshielding (about 5 ppm) will be observed by the H-atom attached on C, which is directly attached to red colored O atom of the ester group. (CH-O-C=O). Note that this is a single H. so option D) is eliminated, as 2 such H are there.

Again this is a heptet, meaning 6 neighboring and equivalent Hydrogens should be there for this H-atom, so option C) is eliminated, as only 4 neighboring hydrogens are there.

For options a) and b) we will analyze by drawing all the hydrogens as below:

Option a) is the correct answer.

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