The alkane molecules are displayed initially as "wireframe" models. Click the appropriate buttons to get "space-filling" models which depict the actual van der Waals radii of the atoms, or to highlight specific sets of atoms. Rotate the models using the mouse; you can return each model to its original orientation at any time by clicking the "Reset model" button.
Exercises to do with these models:
- View the molecules as wireframe models, rotate them to get the appropriate perspective, and practice drawing them using "wedge and dash" and "sawhorse" stereoformulas. Practice until you are able to look at the stereoformula and imagine the three-dimensional molecule.
- Highlight the C's, or both the C's & H's, rotate the models to get the appropriate perspective, and draw each conformation as a Newman projection. Again, practice until you are able to look at the projection and imagine the three-dimensional molecule.
- Compare the space-filling models of the butane conformations. Can you see the origin of the torsional strain and steric strain energies? Highlight the interactions and then select "spacefilling" again.
- Examine the selected pentane conformations shown below to get an idea of the more complicated conformations caused by simultaneous rotations around each of the C-C bonds of higher alkanes. Which should be the most stable conformation?