Chapter 5 Determination of absolute configuration by CD. Applications of the Octant Rule and the Exciton Chirality Rule

Abstract

Publisher Summary The origins of two chirality rules—the Octant Rule for ketones and the Exciton Chirality Rule—are described in this chapter. The chapter highlights the way the rules can be applied to the determination of molecular absolute configuration. In applications of the Octant Rule, when the absolute configuration of a ketone is known, the rule may be used to determine its conformation. The applications of the Exciton Chirality Rule to determine the absolute configuration of diols follows from the derivatization with strongly UV–visible absorbing chromophores. Although chiral molecules may exhibit optical activity as detected by circular dichroism (CD), the focus of understanding is typically the light absorbing unit (chromophore) in the molecule. A chromophore is said to be optically active if it exhibits CD in the region of its UV–visible absorption bands. Any chromophore in a chiral molecule can be expected to exhibit Cotton effects. The Octant Rule has been one of the first, and probably the most successful, of many different chirality sector rule relating Cotton effects (CE's) to organic stereochemistry.