CHM136H1 Lecture Notes - Lecture 9: Joule, Butane, Van Der Waals Strain
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CHM136H1 Full Course Notes
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Document Summary
Hydrogen bonds: the most important non covalent interactions in biological molecules. Stereochemistry: concerned with the 3d aspects of molecules. Rotation is possible around c-c bonds in open chain molecules: ethane. (the molecule is not static) Conformers: different arrangements of atoms resultings from bond. Conformations of ethane: perfectly free rotation from one conformation to another is not observed, barriers to rotation exists: some conformations are more stable than others. The eclipsed conformation is the least stable conformation, and the staggered conformation is the most stable because there are no bonds lying on top of each other. In the case of eclipsed conformation: electron repulsion can occur (steric strain) and raises the energy of the conformation. However, if the conformation is staggered that does not occur. Staggered: lower in energy, all 6 c-h bonds are as far away as possible. Eclipsed: higher in energy all 6 c-h bonds are as close to each other as possible.
