Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space. Optical isomers are named like this because of their effect on plane polarised light.Simple substances which show optical isomerism exist as two isomers known as enantiomers.
- A solution of one enantiomer rotates the plane of polarisation in a clockwise direction. This enantiomer is known as the (+) form.
- A solution of the other enantiomer rotates the plane of polarisation in an anti-clockwise direction. This enantiomer is known as the (-) form.
There are 16 optical isomers of glucose.
D-allose | D-altrose | D-glucose | D-mannose
D-gulose | D-idose | D-galactose | D-talose
L-allose | L-altrose | L-glucose | L-mannose
L-gulose | L-idose | L-galactose | L-talose