The carbon-carbon bonds in alkanes result from the sigma overlap of two tetrahedral carbon sp3 orbitals. Due to this sigma bond symmetry, there is free rotation around the carbon-carbon single bond. The different spatial arrangements that a molecule can adopt due to rotation about sigma bonds are called conformations, and a specific structure is called a conformer (conformational isomer). Unlike other kinds of isomers, different conformers cannot usually be isolated since they interconvert too rapidly. The study of the energy changes that occur during these rotations is called conformational analysis. The objective of the conformational analysis is to identify the preferred conformations of a molecule, and those conformations determine its behaviour.