What is the E-Z designation of the following compound?

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1 Answer
Truong-Son N.
Dec 5, 2017

That is based on the Cahn-Ingold-Prelog (CIP) nomenclature priorities.

And we would get the #E# isomer.

You would consider:

  1. Atomic number of the first atoms around the stereocenter
  2. Going one atom out if there is a tie
  3. Treating multiple bonds as "ghost atoms" in further single-bond branching

In this case, all of these first atoms around the stereocenter are different atomic number. So we only need to consider rule 1 to get:

  • Priority 4 = #"C"_6"H"_5#
  • Priority 3 = #"CH"_3"NH"#
  • Priority 2 = #"Br"#
  • Priority 1 = #"I"#

Then, you divide the molecule in two, bisecting the double bond. This gives a higher priority on #"I"# on the right half and #"CH"_3"NH"# on the left half.

Since #"CH"_3"NH"# and #"I"# are the highest priority on their respective sides of the molecule, this is the #color(blue)(E)# isomer, as they are trans to each other.

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