Science, Tech, Math › Science Periplanar Definition in Chemistry Definition of Periplanar Share Flipboard Email Print These structures show the sawhorse and Newman projections of two periplanar conformations of butane. Todd Helmenstine Science Chemistry Molecules Basics Chemical Laws Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 12, 2020 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. Sources March, Jerry (1985). Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.). New York: Wiley. ISBN 0-471-85472-7.Testa, Bernard; Caldwell, John (2014). Organic Stereochemistry: Guiding Principles and Biomedicinal Relevance. ISBN 390639069.