CHEM 4345 EXAM 3

Dr. Bachrach April 18, 2000

1) (20 points) Suggest an explanation for why cis-1-bromo-4-t-butylcyclohexane undergoes substitution 58 times faster than trans-1-bromo-4-t-butylcyclohexane with NaSPh in 87% aqueous ethanol.

2) (20 points) Suggest a mechanism for the following reaction:

3) (30 points) a) Draw the orbital correlation diagram for the conversion of Dewar benzene into benzene.

b) Is the reaction thermally allowed or forbidden? Is the reaction photochemically allowed or forbidden?

Reaction is forbidden thermally, but allowed photochemically.

4) (15 points) Write the mechanism for the following reaction and predict the stereochemistry of the product.

5) (15 points) Sketch the orbital energy diagram for cyclooctatetraene with Huckel orbital and Mobius orbital arrangements.