In Class Problems - 11/8/00

1.) The bond length of transient diatomic molecular CF is 1.291 Å; that of the molecular ion CF⁺ is 1.173 Å. Explain why the CF bond shortens with the loss of an electron. Use molecular orbital energy level diagrams in your explanation.

2.) The azide ion (N₃^-) is a weakly bound molecular ion. Formulate its molecular orbital structure in terms of localized s bonds and delocalized p bonds. Do you expect N₃ and N₃⁺ to be bound as well? Which of the three species do you expect to be paramagnetic?

3.) Acetic acid can be made by the oxidation of acetaldehyde (CH₃CHO). Molecules of acetaldehyde have a —CH₃ group, and oxygen atom, and a hydrogen atom attached to a carbon atom. Draw the Lewis structure for this molecule, give the hybridization of each carbon atom, and describe the p orbitals and the number of electrons that occupy each one. Draw the three dimensional structure of the molecule, showing all angles.

4. Acrylic fibers are polymers made from a starting material called acrylonitrile, H₂C(CH)CN. In acrylonitrile, a —CºN group replaces an H atom on ethylene. Draw the Lewis structure for this molecule, give the hybridization of each carbon atom, and describe the p orbitals and the number of electrons that occupy each one. Draw the three dimensional structure of the molecule, showing all angles.