Absolute configuration records a spatial arrangement without leaving its handedness relative to its mirror unspecified. R and S configuration is one naming convention; optical rotation is a measured response.
For a tetrahedral stereocenter, rank its four substituents using stereochemical sequence rules. With lowest-priority group pointing away, a clockwise sequence is and a counterclockwise sequence is . Looking from the other side reverses the apparent sequence, so the viewing condition is essential. The geometric letters A/B/C/D in the tetrahedral mirror-image test carry no assigned priority. Neither nor determines positive or negative optical rotation.[ref]
5.5 Sequence Rules for Specifying Configuration. McMurry, Organic Chemistry, §5.5, Figure 5.8 and discussion after Figure 5.10
Stereochemical sequence rules rank substituents for R and S configuration. Compare the directly attached chemical atoms by atomic number first, then resolve ties by comparing successive shells at the first difference. Isotopes and multiple chemical bonds require additional rules. This ranking convention does not involve optical rotation.[ref]
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Absolute configuration refers to the specific three-dimensional arrangement of atoms in a chiral molecule, denoted by terms such as R (rectus) and S (sinister) based on the Cahn-Ingold-Prelog priority rules. These designations provide an unambiguous way to describe the orientation of substituents around a chiral center.