Question

Question: Assign R,S designations to each stereogenic center in glucose.

Short answer

Answer

Configuration in glucose

Step-by-step solution

Glucose

Glucose is aldohexose which means that it contains six carbon atoms with an aldehyde group. The chemical formula for glucose is , and it is a simple sugar.

It can exist in open-chain or cyclic forms. The cyclic structure is formed due to an intramolecular condensation between the aldehyde and hydroxyl groups to form a pyranose structure.

Glucose has four chiral centers, which define its optical activity.

R and S configuration

Enantiomers are identical in structure, and the majority of their properties are the same except for the direction of rotation of plane-polarized light.

Since the IUPAC name of the compounds is the same, configurations for chiral carbon were introduced to distinguish the enantiomers.

This configuration is called R and S configuration are used in which the atoms are ranked based on priority.

If priority order is in the clockwise direction, the compound has an R configuration. If it is anti-clockwise, the compound has an S configuration.

Configuration in D-glucose

Glucose has four chiral centers.

The priority is determined as follows:

• First, consider the atom directly connected to the chiral carbon. Substituents are assigned priority based on their atomic mass. The atom with the highest atomic mass gets the highest priority.
• If the atom directly attached to carbon is the same, consider the next atom, and its mass is considered.
• This is continued till all carbon atoms substituents are assigned priority.

Now, if the direction of priority is clockwise, the configuration is R, and otherwise, it is S.

The configurations of four chiral centers in glucose are:

Configuration in glucose