Alkane Conformations

The alkane molecules will be 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 state at any time by clicking the "Reset" 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 to get an idea of the more complicated conformations caused by simultaneous rotations around each of the C-C bonds of higher alkanes. (It may be easiest to click the checkbox to turn spin off and then move the model manually to examine it.) Which should be the most stable conformation?

Go to:

Butane Conformations




fully eclipsed

Some Pentane Conformations

anti, anti ("zigzag")

anti, gauche

gauche, gauche

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