Chem2O6 - 1997/98

1. You are given a compound with the molecular formula C₄H₈O₃ and are asked to identify its structure. You rush to the NMR lab and obtain the proton and carbon spectra and then tabulate the data as shown below.

Proton NMR Carbon NMR

• What is the structure of the compound?

        Write in the assignment of the various resonances in the space provided in the table above.

• Name the compound.

3-methoxy-propanoic acid

• You are now off to confirm your assignment by running an infrared spectrum. What key features would expect in your ir spectrum?

The key feature would be bands associated with the carboxylic acid group. These would include a large absorption 1700 to 1720 cm^-1 due to the C=O bond stretch and also a broad featureless band associated with the OH group ranging from ca 3400 to 2700 cm^-1.

2. Show how you would convert cyclooctene into the following compounds. Where you propose more than one step clearly show the structure of any intermediate compound.

3. Propose a mechanism for the following acid catalysed transformation. (The acid is a trace of concentrated sulphuric acid added to the methanol solvent.)

Note: Answers in which an alkoxide ion is used to attack the carbonyl carbon are incorrect.

4. What are the principal products of the following reactions?

5. Show how you could accomplish the following synthetic transformation. Note, more than one step is involved. Clearly show the structures of any proposed intermediary compounds and the reagents/conditions used in each step you propose.

30jan98; jp