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 1.653 Å. 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. All three N-H bond lengths were found to be 1.003 Å, and the H-N-H bond angle was found to be 112.27º. The magnitude of the dipole moment for the molecule was found to be 1.76 D. The dipole 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.
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