What is the structure of the molecule with the name (E)-3-benzyl-2,5-dichloro-4-methyl-3-hexene?

1 Answer
Ernest Z.
Jun 9, 2015

The structure of (E)-3-benzyl-2,5-dichloro-4-methylhex -3-ene is

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Explanation:

The real problem here is determining the (E,Z) configuration of the molecule.

You draw a hexane chain with the double bond between #"C-3"# and #"C-4"#, #"Cl"# atoms at #"C-2"# and #"C-5"#, a benzyl group at #"C-3"#, and a methyl group at #"C-4"#.

Determine the priorities of the groups on #"C-3"#.

  • Benzyl. The atoms directly attached to the methylene carbon atom are (#"C,H,H"#).
  • 1-Chloroethyl. The atoms directly attached to #"C-1"# are (#"Cl,C,H"#).

1-Chloroethyl has higher priority than benzyl because #color(lime)"Cl"# has a higher atomic number than #"C"#.

Determine the priorities of the groups on #"C-4"#

  • 1-Chloroethyl. The atoms directly attached to #"C-1"# are (#"Cl,C,H"#).
  • Methyl. The atoms directly attached to the methyl carbon atom are (#"H,H,H"#).
    1-Chloroethyl has higher priority than methyl because #color(lime)"Cl"# has a higher atomic number than #"H"#.

In each case, the 1-chloroethyl group has the higher priority.

These groups must therefore be on opposite sides of the double bond (entgegen).

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