The carbon-carbon single bonds in organic molecules are free to rotate. For molecules with 4 or more carbons, this can lead to different shapes for the same molecule. These different shapes are called conformations. Conformations and isomers are different. A molecule can switch between different conformations by simple rotation about the carbon-carbon single bond. To switch between different isomers requires the the breaking and making of covalent bonds.

A three dimensional model of n-butane. These three structures are all for the same molecule They differ by rotation about the central bond and represent different conformations of n-butane.

Below is a movie that illustrates rotation about the central bond in n-butane.

A movie illustrating rotation about the central bond in n-butane. Double click on the movie to start and stop the animation.