Question

Propose a structure for compound E, ${\mathbf{C}}_{\mathbf{7}}{\mathbf{H}}_{\mathbf{12}}{\mathbf{O}}_{\mathbf{2}}$ , which has the following${}^{\mathbf{13}}\mathbf{C}$ NMR spectral data:

Compound E Broadband-decoupled${}^{\mathbf{13}}\mathbf{C}$ NMR: 19.1, 28.0, 70.5, 129.0, 129.8, 165.8$\mathbf{\delta }$ DEPT-90: 28.0, 129.8$\mathbf{\delta }$ DEPT-135: positive peaks at 19.1, 28.0, 129.8$\mathbf{\delta }$ ; negative peaks at 70.5, 129.0$\mathbf{\delta }$

Short answer

Structure as follow:

Step-by-step solution

13C NMR

Carbon-13 nuclear magnetic resonance is the technique similar to the NMR which is used to identify the carbon from the organic molecules or from the organometallic compounds like hydrogen is detected in NMR but its only sensitive to carbon-13 not carbon-12.

Structure elucidation of compound E as per data

As per the data given the peak is observed at the 165.8 the positive peak that must be a carbonyl group present in the compound and then the peak is observed at the 129.8 shows the presence of an unsaturated bond present in the molecule and peak at 19.1 is due to the protons of the methyl group which is shown by DEBT 135.

Structure of compound E

So, per the peaks given and the presence of the ketonic group shows that the structure of compound E is:

Compound E