Chapter 4, Problem 35P

Interpretation Introduction

Interpretation:

The configuration of the chirality center as R or S is to be determined for the given compounds.

Concept introduction:

If a tetrahedral carbon is attached to four different atoms or groups, then such carbon is called a chiral carbon or chiral center.

The three-dimensional spatial arrangement of substituents at a chirality center is called the absolute configuration.

The Cahn-Ingold-Prelog rule system ranks the substituents in the chirality center in the order of decreasing atomic number. The higher atomic number takes precedence over the lower atomic number.

When two or more of the atoms directly bonded to the chirality center are same, compare the atoms bonded to the chirality center on the basis of their atomic numbers. The priority order is determined at the first point of difference.

Work outward direction from the point of attachment by comparing all the atoms attached to a particular atom before continuing further along the chain.

When working outward direction from the point of attachment, always estimate substituent atoms one by one, never as a group.

After the substituents at the chiral center are ranked with decreasing priority order, the next step is to orient the molecule so that the bond to the lowest ranked substituent points away from the observer. This is used to determine if the sequence of decreasing priority of the other three substituents is clockwise or counterclockwise. If this path is clockwise, then the configuration is R, and if it is counterclockwise, the configuration is S.