1. (2 points) Arrange the following in order of decreasing energy (1 for highest to 4 for lowest):
C-H stretch ( 3 )
C-Br stretch ( 4 )
p -> p * transition (alkene) ( 1 )
p -> p * transition (diene) ( 2 )
2. (2 points) Explain how you might use IR to follow the progress of the reaction in which 2-pentanol is dehydrated to a mixture of pentenes. Describe the actual experimental steps you would take and how you would interpret your observations.
During the reaction, remove a small sample and take an IR spectrum. As the alcohol is dehydrated, the O-H stretch at about 3300 cm-1 will gradually disappear (if the experiment is designed to remove H2O, which will also absorb in the same region) and a C=C stretch at about 1600 cm-1 will increase.
3. (6 points) Identify the unknown compound from its spectral data (on the back). Assign all NMR absorptions and at least three IR absorptions.
C-H stretching ~2900 cm-1