Which group in the following pair is assigned the higher priority in R,S
nomenclature
−CH2Cl, −CH2CH2CH2Br
R,S nomenclature is important in organic chemistry.
In order to identify the configurational nomenclature of molecules, scientists develop a new system of nomenclature known as the CIP system of nomenclature. According to this system of nomenclature, the configuration is either labelled as R or as S configuration. In order to assign the configuration, the following rules are followed,
The different groups attached to the chiral carbon are arranged in their priority order and the molecule is viewed from the side opposite to the least priority group. On viewing from the least priority group to highest priority group if the eye rotates in a clockwise direction then the configuration is said to be R-configuration, if the eye rotates in an anticlockwise direction then the configuration is said to be S-configuration.
The priority is assigned by the following the rules,
1) The priority of the different atoms depends upon the atomic number of each atom, that is a higher priority is assigned to the atom which has a higher atomic number and a lower priority to the atom having the lowest atomic number.
2) When two or more atom that is directly attached to the chiral carbon has the same priority then the priority is determined by a similar comparison of the next atom in the group.
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