Periplanar Definition in Chemistry

Periplanar refers to two atoms or groups of atoms in a conformation are in the same plane with respect to the reference single bond. The image shows two conformations of butane (C4H10). The methyl groups (-CH3) are lined up in the same plane with the middle carbon-carbon single bond. The top conformation is known as syn-periplanar and the bottom is known as anti-periplanar.