# How do you determine r and s for Fischer projections?

## How do you determine r and s for Fischer projections?

If the curve goes clockwise, the configuration is R; if the curve goes counterclockwise, the configuration is S. To get the number-four priority substituent at the top of the Fischer projection, you have to use one of the two allowed moves diagramed in the second figure.

## What is the difference between R and S enantiomers?

R isomer has its relative direction of the priority order in the clockwise direction. S isomer has its relative direction of the priority order in an anticlockwise direction. The letter “R” comes from the Latin word “Rectus” meaning, “Right-handed”. The letter “S” comes from the Latin word “Sinister”.

What is the R and S configuration of glucose?

For L-glucose, it has the configuration (2S,3R,4S,5S). As a general rule, for an enantiomer, all S will change to R and vice versa at each respective carbon centres. For example, (R,R) and (S,S) are enantiomers, (R,S) and (S,R) are enantiomers, but (R,R) and (R,S) are diastereomers.

### What is the difference between R and S?

The key difference between R and S configuration is that the R configuration is the spatial arrangement of R isomer, which has its relative direction of priority order in a clockwise direction whereas S configuration is the spatial arrangement of S isomer that has its relative direction of priority order in an …

### How to determine your and S configurations on a Fischer projection?

Now Trace A Path From Priorities 1-2-3 To Determine R or S. Recall that the Cahn-Ingold-Prelog (CIP) rules for determining R and S configurations outline a set of rules for assigning priorities (1, 2, 3, and 4) to each of the groups assigned to a chiral center.

What is rule 2 in a Fischer projection?

Rule 2: Rotation of three ligands on the chiral center in either direction, keeping the remaining ligand in place, does not change the absolute configuration at the chiral center. The operations that do change the absolute configuration at a chiral center in a Fischer projection can be summarized as two rules.

## How do you assign priority to ligands in Fischer projection?

Assign priority numbers to the four ligands on the chiral center (see R,S convention). If the lowest-priority ligand is on a horizontal bond, meaning that it is pointing toward the viewer, trace the three highest-priority ligands starting at the highest-priority ligand ( ① → ② → ③ );

## How is a Fischer projection used in chemistry?

A Fischer projection or Fischer projection formula is a convention used to depict a stereoformula in two dimension without destroying the stereochemical information, i.e., absolute configuration, at chiral centers. eg: (R)-Lactic acid To convert this stereoformula into a Fischer projection use the following procedure: