Question

Is this the correct name for this structure, why or why not?

(3S,42,6E,9R, 10E)-7-chloro-3,6,9-trimethyltrideca-4,6-diene

Answer 1

The provided name in the question is incorrect. The right name for this structure is (3E,5S,7E,9Z,11S)-7-chloro-5,11-dimethyltrideca-3,7,9-triene

Point 1: According to the IUPAC rule, in the parent chain where unsaturated carbon atoms are present, the unsaturated carbon atom with lowest atom count should be considered at first. The counting from left end of the parent chain gives the number 4 for the unsaturated bond whereas for the counting from right end of the chain gives 3 for the unsaturated carbon. Thus, in the parent chain the atom numbering of carbon atoms starts from right end of the chain.

Point 2: The double bond at 3 position has E configuration because the first two prioritized groups are in anti position to each other.

Point 3: At 5 position the carbon center is chiral, and the lowest priority group H is already in the back. The first priority group is the group where the double bond is in the alpha carbon to the chiral center. The second priority group is the group where the double bond is in the beta carbon to the chiral center. The methyl group is the third priority group. Thus its going anti clockwise. Hence, the chiral carbon has S configuration.

Point 4: For the E or Z configuration of the carbon at 7 position, the Cl group is considered the first priority group. Here also, the two first priority group is in anti position to each other. Thus the carbon at 7 position has E configuration.

Point 5: For the carbon atom at 9 position, the first two prioritized groups are syn to each other. Therefore, the carbon atom at 9 position has Z configuration.

Point 6: The chiral carbon at 11 position has the first priority group as the chain where the alpha carbon is unsaturated. Then the ethyl group is next priority group, and then the methyl group. The lowest priority group is the H which is above the plane. Thus, the hand rule goes clockwise but the H is in above the plane. Therefore, the chiral carbon has S configuration.

Point 7: The parent chain has 13 carbon atoms, therefore, it has trideca name for the parent chain. The substituents are named according to their positions.