Question

Question: Propose a structure of compound C (molecular formula ${\mathbf{\text{C}}}_{\mathbf{\text{10}}}{\mathbf{\text{H}}}_{\mathbf{\text{12}}}\mathbf{\text{O}}$) consistent with the following data. C is partly responsible for the odor and flavor of raspberries. Compound C: IR absorption at 1717 cm–1.

Short answer

Answer

Structure of compound C

Step-by-step solution

Upfield and downfield shift of protons

In monosubstituted benzene, the peak of the aromatic protons is a multiplet due to many J values and overlapping.

Deshielded protons have downfield shifts, and shielded protons have an upfield shift. The terms upfield or downfield explain the relative position in the NMR spectra.

Structure determination based on NMR and IR data

One singlet at 2.1 ppm - 3 hydrogens - must be present.

Triplets at 2.8 ppm - 2 hydrogens - 2 H’s adjacent to 2 H’s

Triplets at 2.9 ppm - 2 hydrogens - 2 H’s adjacent to 2 H’s

Therefore, two CH₂ groups must be directly attached to an electronegative group, e.g., Oxygen.

Multiplet at 7.1 - 7.4 ppm - 5 hydrogens - monosubstituted benzene.

The IR stretching frequency around 1717 confirms the presence of a carbonyl group.

The structure of compound C based on the data can be represented as:

Structure of compound C