Stereoisomerism
Sugars are complicated by isomerism. A carbon with 4 different groups attached is asymetric. This means that it can have D- or L- isomers. Optical isomers is also used as a name because these isomers can rotate the plane of polarized light. You can think of right or left handedness.

PLEASE CONSIDER :

Carbon is often pictured as the central atom in a pyramid with other atoms at each apex. In other words, this pyramid represents a carbon atom. The colored balls are other groups with many, many possibilities such as methyl, ethyl, chlorine, benzene ring, etc.

All the representations of sugar structures are distortions as the spatial arrangements are forced to the plane of the computer terminal. Consider looking down at pyramids that have a yellow group bonded to the top. The black group is at the back of each. The base of #1 is red, black, blue in clockwise order. The base of #2 has blue, black, red in clockwise order and is an isomer.

  • Suppose two groups are the same ?

    • Sugars have several asymetric carbon atoms. Sugars differ in reactivity, and in properties such as solubility and sweetness. Let's learn a quick way to draw sugars. A stick will represent the chain of carbons. An arrow head stands for the aldehyde group. A circle stands for the CH2OH. A projecting line = an OH.

    We can simplify the system by defining all sugars with the the next to last -OH on the right as D- sugars.

  • How to remember pentose structures.
  • More about sugars

    • Last update 28-Dec-95