An unknown compound A has the molecular formula C₇H₁₄O₂.Compound A absorbs strongly in the IR at 1700 cm^-1.The ¹H NMR spectral data for compound A are given below.What is the structure of compound A?

Question

Quizplus · Accepted Answer

- The molecular formula of compound A indicates it contains two sulfur atoms and a significant number of carbon and hydrogen atoms.
- The strong absorption in the IR spectrum at 1700 cm-1 suggests the presence of a carbonyl group (C=O).
- The 1H NMR spectrum provides the following information: 
  - A singlet at ~1.5 ppm, which corresponds to 3H, is likely due to a methyl group (CH3). 
  - A singlet at ~2.3 ppm, which corresponds to 3H, is likely due to another methyl group. 
  - A singlet at ~3.7 ppm, which corresponds to 3H, is likely due to a methoxy group (OCH3).
  - A singlet at ~9.5 ppm, which corresponds to 1H, is likely due to an aldehyde (CHO) proton.
- The 13C NMR spectrum provides the following information:
  - There are 12 peaks, which match the number of carbons indicated by the molecular formula. 
  - There are two carbons that are highly shielded (at ~15 ppm), likely because of their proximity to sulfur atoms. 
  - There is a peak at ~200 ppm, which is characteristic of a carbonyl carbon. 
- Putting all of this information together, we can propose the following structure:

III: 
  - Contains two sulfur atoms, as indicated by the molecular formula.
  - Contains a carbonyl group (C=O), as indicated by the IR spectrum. 
  - Contains a methyl group at ~1.5 ppm and another methyl group at ~2.3 ppm, as indicated by the 1H NMR spectrum.
  - Contains a methoxy group at ~3.7 ppm, as indicated by the 1H NMR spectrum. 
  - Contains an aldehyde group (CHO), as indicated by the 1H NMR spectrum.
  - Contains 12 carbons, including a carbonyl carbon at ~200 ppm, as indicated by the 13C NMR spectrum.

Therefore, the best choice is C.

An Unknown Compound a Has the Molecular Formula C7H14O2

An Unknown Compound a Has the Molecular Formula C₇H₁₄O₂