1. Draw the Lewis structures of the following molecules and ions in their correct geometrical shape and indicate the approximate bond angles.
a. methylcyanide, CH3CN.........................................b. acetate ion, CH3COO-.
2.a. Do you expect the propylamine molecule, CH3CH2CH2NH2 to possess a dipole? Explain your answer.
b. What type of bonds do we encounter in the liquid propylamine? Specify your answer for the bond types between the atoms in the molecules, and the bond types between the molecules.
3. Carbonate ions, CO32- exhibit resonancy. Explain what that is and show Lewis structures and curved arrows to illustrate your answer.
4. Describe all the molecular orbitals (M.O.'s) in compound a., and all C-C and the C-Br M.O.'s in compound b.
5. a. What is cis-trans isomerism? Give a definition and show an example to
illustrate it.
b. From the two molecules drawn here explain why the one on the right has the lower boiling point. Use key terms such as electro-negativity, polar covalent and non-polar covalent bonds, and polar and non-polar molecules.
6. Do not memorize all the functional groups as of yet. Just know: the alkenes, alkynes, halides, the alcohols, and the ethers. The halides are derived from the halogens fluorine, chlorine, bromine, iodine and the very rare one astatine.
The alcohols have the OH functional group which is capable of hydrogen bond forming. Realize, that the hydrogen bond is occurring between the molecules not within a molecule!
For example, methanol is CH3OH and isopropyl alcohol is CH3CH(OH)CH3.
These substances have relatively high boiling points because the molecules attract each other strongly with forces that are a sum of LDF + DDF + HB, in which HB are by far the strongest ones. You notice that your text book uses van der Waals forces for LDF and DDF, that is an acceptable name, after all van der Waals is a Dutchman.......Know the alkyl groups methyl, ethyl, propyl, isopropyl and the four butyls!
JD/August 2008