Dextrorotatory
Definition and meaning of Dextrorotatory in chemistry.
Dextrorotatory describes a chiral, optically active substance that rotates the plane of plane-polarized light clockwise (to the right), as seen by an observer looking toward the oncoming light source. Such compounds are labeled with a "(+)" or "d-" prefix before the name.
In more detail
The rotation arises because a chiral molecule interacts slightly differently with the left- and right-circularly polarized components that make up plane-polarized light, shifting the plane of polarization as the light passes through. The angle of rotation is measured with a polarimeter and reported as the specific rotation, [α], which depends on concentration, path length, wavelength, and temperature. Importantly, "dextrorotatory" is a purely empirical, measured property; it does not by itself reveal the molecule's absolute (R/S) configuration, since these two labeling systems are determined independently.
Key facts
| Field | Organic Chemistry |
|---|---|
| Symbol | (+) or d- |
| Measured with | Polarimeter |
| Common example | D-glucose, [α]D = +52.7° |
D-glucose (dextrose) is dextrorotatory, with a specific rotation of [α]D = +52.7° in aqueous solution, meaning it turns plane-polarized light clockwise.
Frequently asked questions
Does dextrorotatory always correspond to the R configuration?
No. The direction of optical rotation (+ or -) is an experimentally measured physical property, while R/S designates the spatial arrangement of substituents around a stereocenter; the two are not directly correlated and must be determined separately.
What is the opposite of dextrorotatory?
Levorotatory, denoted (-) or l-, describes a substance that rotates plane-polarized light counterclockwise.