Final answer:
Stereochemical designations such as R/S and E/Z provide information on the spatial arrangement of atoms within a molecule, especially at chiral centers and around double bonds. R/S denotes the absolute configuration of chiral centers, while E/Z describes the arrangement of substituents around double bonds.
Step-by-step explanation:
The stereochemical designation of a given compound refers to the spatial arrangement of its atoms. The descriptors R or S are used to denote the absolute configuration of chiral centers in molecules, which are carbons bonded to four different groups. To determine this, assign priorities 1 through 4 to the substituents attached to the chiral center, follow the rules by Cahn, Ingold, and Prelog, and observe the orientations from high to low priority. If the sequence follows a clockwise direction, the stereocenter is designated as R (from the Latin 'rectus', meaning 'right'), and if anticlockwise, it's an S (from 'sinister', meaning 'left') isomer.
E and Z stereoisomers describe compounds with multiple substituents around a double bond. 'E' stands for 'Entgegen', meaning 'opposite' and signifies that the higher priority groups are on opposite sides of the double bond. In contrast, 'Z' (from 'Zusammen', meaning 'together') indicates that the higher priority groups are on the same side. The D/L designation indicates the configuration of sugars and amino acids based on the position of specific groups in a Fischer projection, not directly related to optical activity as dextrorotatory (+) or levorotatory (-) can describe either R or S configurations.