The first task is to assign the principal axis, and to do this, the priority of each of the six ligands around the platinum ion is assigned using the CIP rules as shown below. The chlorine atoms are ranked 1 since chlorine has a higher atomic number than nitrogen, and the nitro groups are ranked 2 since the second atoms in the nitro groups (ie the oxygen atoms) have a higher atomic number than the second atoms (hydrogen) in the amino groups. The principal axis is then defined as the axis containing a ligand of rank 1, the metal, and with the ligand trans to the ligand of rank 1 of as high a priority as possible. In this case, this is the axis shown in red in the diagram below. Next, the molecule is viewed along the principal axis with the ligand of rank 1 towards the viewer, the rotatable 3D structure shown below may assist in this. The three highest ranking ligands in the plane perpendicular to the principal axis are then observed to decrease in priority in an anti-clockwise direction, so this is the (A)-enantiomer of the complex.
The compound contains a stereogenic axis along the allene bonds. The compound is first viewed along this axis, the rotatable 3D structure shown below may assist in this, and the four substituents are ranked into an order of priority using the CIP rules. It does not matter which end of the axis is chosen as the front end. Rule 0 says that substituents at the front of the axis have a higher priority than those at the rear, and CIP rule 1 then allows the relative ranking of the two front and two rear substituents to be determined since carbon has a higher atomic number than hydrogen. The three groups of highest priority decrease in priority in an anti-clockwise direction as shown below, so this is the (S)-enantiomer.
The compound contains a stereogenic axis along the exo-alkylidene ring system as shown below. The compound is first viewed along this axis, the rotatable 3D structure shown below may assist in this, and the four substituents are ranked into an order of priority using the CIP rules. It does not matter which end of the axis is chosen as the front end. Rule 0 says that substituents at the front of the axis have a higher priority than those at the rear, and CIP rule 1 then allows the relative ranking of the two front and two rear substituents to be determined since carbon has a higher atomic number than hydrogen. The three groups of highest priority decrease in priority in an anti-clockwise direction as shown below, so this is the (S)-enantiomer.
The compound contains a stereogenic axis along the spirocyclic ring system as shown below. The compound is first viewed along this axis, the rotatable 3D structure shown below may assist in this, and the four substituents are ranked into an order of priority using the CIP rules. It does not matter which end of the axis is chosen as the front end. Rule 0 says that substituents at the front of the axis have a higher priority than those at the rear, and CIP rule 1 then allows the relative ranking of the two front and two rear substituents to be determined since nitrogen has a higher atomic number than hydrogen. The three groups of highest priority decrease in priority in an anti-clockwise direction as shown below, so this is the (S)-enantiomer.
The compound contains a stereogenic axis along the spirocyclic ring system as shown below. The compound is first viewed along this axis, the rotatable 3D structure shown below may assist in this, and the four substituents are ranked into an order of priority using the CIP rules. It does not matter which end of the axis is chosen as the front end. Rule 0 says that substituents at the front of the axis have a higher priority than those at the rear, and CIP rule 1 then allows the relative ranking of the two front and two rear substituents to be determined since oxygen has a higher atomic number than nitrogen. The three groups of highest priority decrease in priority in an anti-clockwise direction as shown below, so this is the (S)-enantiomer.
The compound contains a stereogenic axis along the bond joining the two aromatic rings as shown below. The compound is first viewed along this axis, the rotatable 3D structure shown below may assist in this, and the four substituents are ranked into an order of priority using the CIP rules. It does not matter which end of the axis is chosen as the front end. Rule 0 says that substituents at the front of the axis have a higher priority than those at the rear, and CIP rules 1 and 2 then allow the relative ranking of the two front and two rear substituents to be determined. The three groups of highest priority decrease in priority in an anti-clockwise direction as shown below, so this is the (S)-enantiomer.
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