1) An unknown organic compound has a molecular formula of C₄H₈O. The compound is non-cyclic and contains a double bond. The infra-red (IR) spectrum of the molecule is shown below

a. What does the region 3100–4000 cm^-1 indicate about the bonds in
C₄H₈O? Give your reasoning.

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Solution

b. The ¹³C NMR spectrum of the unknown compound has four distinct peaks. Draw two possible structural formulas of the unknown compound using the information provided.

Solution

c. The high-resolution ¹H NMR spectrum of the unknown compound has three single peaks, as shown below.

Refer to the ¹H NMR spectrum and the table of spectrum information provided above. Identify three pieces of information about the unknown compound and indicate how each would assist in determining its structure.

Solution

d. C₃H₆O can exist as a ketone or as a primary alcohol. Explain how the principles of IR spectroscopy and ¹H NMR spectroscopy lead to different spectra for the ketone and primary alcohol isomers of C₃H₆O, which can then be used to differentiate between the two molecules.

Solution