Results and Discussion
The shapes and polarities of several molecules were first determined by use of the VSEPR model
and were then compared with the results obtained from using a computer software program known
as Spartan which performs quantum mechanical calculations.
A pharmaceutical drug molecule was
then designed with the intention of the molecule having the capability to favorably react with a
known receptor site.
First, an ammonia molecule was built using Spartan.
The program was then used to measure the
bond length of each N-H bond in the ammonia molecule, the distance between two hydrogen atoms
in the molecule, the H-N-H bond angle, and the N-H-H bond angle.
All three N-H bonds were
found to have lengths of 1.012 Å, and the distance between two hydrogen atoms was found to be
All three H-N-H bond angles were found to be 109.47º, and the N-H-H bond angle was
found to be 35.26º.
Spartan was then used to optimize the ammonia molecule, meaning that the geometry for which the
molecule has the lowest energy was determined.
After optimizing the structure, the N-H bond
lengths, H-N-H bond angles, the magnitude and direction of the molecule’s dipole moment, and the
partial charges of the hydrogen atoms and the nitrogen atom were measured using the program.
three N-H bond lengths were found to be 1.003 Å, and the H-N-H bond angle was found to be
The magnitude of the dipole moment for the molecule was found to be 1.76 D.
arrow pointed away from the hydrogen atoms.
The partial charge of each hydrogen atom was 0.423,
and the partial charge of the nitrogen atom was -1.267.