MU - Chemistry 210 - WS99
IAE on Intermolecular Forces



Let's begin with a table providing an overview of the types and magnitudes of Inter- and Intramolecular Forces. Note that the energies are given in kJ/mol (SI units) and you need to divide by 4.2 to obtain the energies in kcal/mol. A word of caution: The range of 40 - 0.05 kJ/mol for London dispersion is way too big. It should say 4 - 0.05 kJ/mol (less than 1 kcal/mol).



ScienceNet's Glossary on Intermolecular Forces merely gives verbal definitions of the types of intermolecular interactions. The ideas come to live on Michael Blaber's page on Intermolecular Forces. Blaber's page contains nice graphical illustrations of the various kinds of intermolecular interactions.



Now let's take a look at hydrogen bonding in water. Every water molecule acts twice as an H-bonding donor and twice as an H-bonding acceptor. Take a look at Andersen's animation of a water molecule hydrogen-bonded to other water molecules to illustrate the local environment of a fully H-bonded water molecule.



Must-see Quicktime Movies and Virtual Reality Displays of Water and Ice! In liquid water, all molecules translate and rotate and H-bonds are constantly broken while new ones are formed. View the movies that show the dynamics of the hydrogen bonding in water. After viewing the movies, take a look at the static "snapshots" of the not-so-perfect H-bonding network in liquid water and of the perfect H-bonding network in ice. Try to view the virtual reality worlds if your system has the VRML plug-in. The VR allows you to walk right into the ice and look around.



Must-see CHIME displays of research level structures of DNA base pairs and of the enzyme photolyase. Hydrogen bonding is of critical importance for the structures of biopolymers. DNA contains the thymine-adenine and guanine-cytosine base pairs and both of them are held together by strong hydrogen bonds. Take a look at Glaser's ab initio theoretical structures of the thymine-adenine base pair and the guanine-cytosine base pair. Can you see where the H-bonds are? How many are there in each pair? As an example for the wonderful complexity of protein structure, take a look at "photoylase". Photolyase is the enzyme that repairs DNA photodamage that resulted in the formation of thymine dimers. Note that the structure shown is the actual molecular structure which was determined only in 1997. Ain't it cool?