L

Levorotatory

(−)-rotation: [α]_D < 0; counterclockwise rotation of polarised light
Quick Reference
Formula / Notation(−)-rotation: [α]_D < 0; counterclockwise rotation of polarised light
Also Known As(−)-rotation, laevorotatory, l-rotation, counterclockwise optical rotation

What is Levorotatory?

A term describing an optically active compound that rotates plane-polarized light in a counterclockwise direction (to the left) when viewed facing the oncoming light. Designated with a (-) or l- prefix. The opposite of dextrorotatory.

Formula & Notation

(−)-rotation: [α]_D < 0; counterclockwise rotation of polarised light

Other Names / Synonyms: (−)-rotation, laevorotatory, l-rotation, counterclockwise optical rotation

Properties & Characteristics

Levorotatory describes a chiral compound that rotates the plane of plane-polarised light counterclockwise (to the left) when viewed facing the light source. Designated (−) or l-. The degree of rotation depends on concentration, path length, solvent, and temperature, and is characterised by the specific rotation [α]_D (sodium D-line, 589 nm). Levorotatory does not directly indicate absolute configuration (S or R); only optical rotation direction is implied.

Uses & Applications

Optical rotation measurements are used for: characterising chiral molecules, monitoring asymmetric synthesis reactions, determining enantiomeric excess (ee), quality control of pharmaceuticals and natural products (sugar analysis, amino acid configuration), and forensic identification of controlled substances.

Safety Information

Levorotatory enantiomers of certain drugs are more potent or more toxic than their dextrorotatory counterparts. Thalidomide: R-(+) is sedative, S-(−) is teratogenic. Regulation of chiral drugs requires both enantiomers to be assessed for safety and efficacy individually.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Levorotatory
Formula (−)-rotation: [α]_D < 0; counterclockwise rotation of polarised light
Synonyms (−)-rotation, laevorotatory, l-rotation, counterclockwise optical rotation

Frequently Asked Questions

A term describing an optically active compound that rotates plane-polarized light in a counterclockwise direction (to the left) when viewed facing the oncoming light. Designated with a (-) or l- prefix. The opposite of dextrorotatory.

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