Content area
Full Text
Over the years, organic chemists have paid close attention to our use of language to describe our science, particularly in stereochemistry, where entire articles have been devoted to the pursuit of precision (1-4). However, one term in particular, "periplanar", has not been subject to such scrutiny. The purpose of this commentary is to alert organic chemists to the fact that current usage of this term is linguistically incorrect.
Many textbooks describe the E2 elimination reaction as proceeding via an antiperiplanar transition state and typically go to some length to describe the planarity of the system. Why then the use of the peri prefix? "Peri" is derived from the Greek for "near", and hence its use is clear in terms such as pericyclic or perigee (the closest approach to the earth of an object in orbit). In fact, the term periplanar was coined by Klyne and Prelog (5) to mean "approximately planar", with a deviation of +/-30 deg, in this way allowing the terms synperiplanar, synclinal, anticlinal, and antiperiplanar to cover the full range of conformations (Fig. 1). The "clinal" term does not require the "peri" prefix because it does not specify any particular non90 deg...