1. A conformation of an acyclic molecule is a specific disposition of atoms in the molecule in space within the molecule due to free rotation around bonds.
eg: ethane (CH3CH3)
Due to free rotation around the carbon-carbon bond, the ethane molecule could assume an infinite number of conformations, two of which are shown below as saw-horse formulas.
In the eclipsed conformation of ethane the smallest dihedral angle is 0º, whereas in the staggered conformation it is 60º, which can be seen more clearly in the respective Newman projection.
In other conformations of ethane the smallest dihedral angle could be any value between 0º and 60º.
2. A conformation of a cyclic organic molecule is a specific shape the ring could assume.
Due to the flexibility of the ring, the cyclohexane ring could assume an infinite number of conformations, three of which are given below.
see also conformer, configuration