Q87E - Organic Chemistry (Mcmurry)

Question

The proton NMR spectrum for a compound with formula C₁₀H₁₂O₂ is shown below. The infrared spectrum has a strong band at . The broadband-decoupled ¹³C NMR spectral results are tabulated along with the DEPT-135 and DEPT-90 information. Draw the structure of this compound.

Step-by-Step Solution

Answer

                              Assignment of ¹H NMR spectrum

                           Assignment of ¹³C NMR spectrum

Step 1: DEPT

By combining the DEPT-45, DEPT-90 and DEPT-135 spectra, it is possible to determine multiplicity of each carbon signal. The DEPT-135 gives signals of all protonated carbons but the signals of quaternary carbons are absent in all the DEPT spectra. The analysis of ¹³C DEPT is done on the basis of the following observations represented as:

                        Analysis of ¹³C DEPT

 

Step 2: Structure of the compound

The assignment of the ¹H NMR spectrum of the molecule is as follows:

                      Assignment of ¹H NMR spectrum

The IR peak at $1711 {\mathrm{cm}}^{-1}$ and ¹³C NMR peak at 207 ppm confirms a carbonyl group of carbon. The assignment of the ¹³C NMR spectrum of the ketone A is as follows:

                           Assignment of ¹³C NMR spectrum