Final answer:
The configurations of chiral centers in a compound are determined by assigning R or S descriptors based on substituent priority, with enantiomers being non-superimposable mirror images. For a single chiral center, two enantiomers exist, and for compounds with multiple chiral centers, the number of stereoisomers is given by 2 to the power of n.
Step-by-step explanation:
Chiral centers in compounds are sp3-hybridized carbon atoms with four different substituents attached to them, leading to non-superimposable mirror images known as enantiomers. The configurations of chiral centers can be designated using the R or S system based on the priorities of the substituents
For a molecule with a single chiral center, there are two enantiomers, which can be described using the D/L system or the R/S system. A simple example is glyceraldehyde, which has two enantiomers: D-glyceraldehyde and L-glyceraldehyde. In the case of compounds with more than one chiral center, like erythrose with two asymmetric carbons, the number of possible stereoisomers can be calculated using the formula 2n, where 'n' is the number of chiral centers.
The R or S descriptor for Fisher projections is determined by the orientation of substituents around the chiral center, with horizontal lines representing bonds coming out of the plane and vertical lines going behind the plane. Each chiral center is assigned an R or S configuration based on the Cahn-Ingold-Prelog priority rules.