What is difference between dextro and laevo rotation?

Answer 1

Useful definitions:

• Dextro: Right
• Laevo: Left
• Enantiomer: mirror form of a molecule
• Chiral: a molecule lacking an internal plane of symmetry that can be found in two non-superimposable mirror forms.

The mirror images of a chiral molecule are known as enantiomers, one will be designated Dextro (D-) and the other Laevo (L-).

This behaviour is exhibited by organic molecules containing an asymmetric Carbon atom e.g. D-Glucose, L-Cysteine, etc, enzymes are chiral and tend to selectively catalyse a single enantiomer.

Chiral molecules that are optically active will rotate plane polarised light passing through them, l- enantiomers will rotate the polarisation to the Left, d- enantiomers will rotate it to the Right.

Note the capitalisation L/D refers to the stereochemistry of the molecule relative to that of Glyceraldehyde - l/d tells you which way the polarisation will be rotated. The IUPAC discourages the use of l/d notation as it can be confusing +/- is prefered.

Answer 2

Dextro and laevo refer to the direction in which a substance rotates plane-polarized light. Dextro (d-) rotates light clockwise, while laevo (l-) rotates it counterclockwise. The terms are used to describe the optical activity of a molecule.