MU - Chemistry 210 - WS99
IAE on Intermolecular Forces
Let's begin with a table providing an overview of the types and
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
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
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
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
base pair. Can you see where the H-bonds are? How many are there in
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?