Homework Assignment 1

Due Monday, October 13

Bonding

2.  For the compound in problem 1, show the bonding and antibonding molecular orbitals for the alkene double bond, the alkyne triple bond and the amide group. Include the nitrogen with its nonbonding pair as part of the molecular orbital picture for the amide group.

(compound from problem 1)

6.  When we look at concerted reactions, we need to be able to draw the HOMO and the LUMO for various pi systems. The important ones are those for a simple alkene, a conjugated diene, and a conjugated triene. For each of these pi systems, show the p atomic orbitals that would be used to construct the bonding and antibonding molecular orbitals and decide which molecular orbital is the HOMO and which the LUMO for the system. Remember that you need to get one molecular orbital for each atomic orbital you start with. In drawing the orbital picture, use symmetry to decide how the orbitals interact. Determine the symmetry/antisymmetry for each orbital.

Photochemistry

1.  Colored substances contain highly conjugated pi systems. Laundry bleach, which consists of sodium hypochlorite and acts as a chlorinating agent, is used to remove colored stains. Try to explain how laundry bleach works.

2.  Forensic scientists can determine if a dark stain at a crime scene is blood by using an enzyme found in blood. If the stain is blood, an intense pink color will develop. The color is due to the same substance produced when base is added to phenolphthalein. This enzyme catalyzes the following reaction.

    Explain why the change in structure leads to the intense color. Think about resonance possibilities.