Short and Simple tricks for assign R and S configuration
Students consider stereochemistry as one of the difficult topics in organic chemistry. Assigning R/S configuration is one of them. Many methods are available for assigning R/S configuration like Cahn, Ingold, and Prelog but this method involves rotation of covalent bonds, which many students are not comfortable with and it is a time-consuming method.
Here we are presenting a short and simple method for assigning R/S configuration without rotating bonds. If you study properly you can assign R/S configuration within 5 seconds irrespective of groups.
Rule 1 – Assign Priority
Rule 2 – Select above the plane or below group and not consider while drawing ascending order clockwise or anti-clockwise curve. Select one group above the plane or below the plane. Do not consider this group while drawing the ascending order clockwise or anticlockwise curve.
Rule -3 Check the sign of the hidden group if it is +ve means no change in configuration and -Ve indicates a change in configuration.