Question

Camino College-CHEM 20-S X nglearning.com/ibiscms/mod/ibis/view php?id 7833629 Print Calcu etor Periodic Table n 4 of 26 Sapling Learning acid (0Z 12Z-octadecadienoic acid) is a precursor for the eicosanoids, which are important lipid g molecules that include prostaglandins and leukotrienes. It is an essential fatty acid because it cannot be made de novoin mammals. Draw the line-bond structure of linoleic acid. Clearly show stereochemistry where needed. Hint Check Answer Next E

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Answer 1

OH linoleic acid

IUPAC naming rules are given below. Using the same one can deduce the structure from the name as well.

IUPAC Naming

1. Find out the parent (longest) hydrocarbon chain.

2. Identify the functional groups and substitutions present.

3. Give numbering to the carbon atoms in the parent chain. The highest priority substitution/functional group should get lowest number possible.

4. If any stereocenter is present assign R or S configuration based on Cahn-Ingold-Prelog rules

5. If there double bond is present assign E or Z configuration

While writing down the name of substitutions should be in alphabetical order.

E/Z Nomenclature

First find out the priority group on the both ends of double bond using Cahn Ingold Prelog rules. If the higher priority group at one end of the double bond and the higher priority group at the other end of the double bond are on the same side assign Z to the double bond and if it is on opposite sides assign E to the double bond.

Cahn-Ingold-Prelog rules

First, examine at the atoms directly attached to the stereocenter of the compound (here only substituents shown not full compound). A substituent with a higher atomic number takes precedence over a substituent with a lower atomic number. Hydrogen is the lowest possible priority substituent, because it has the lowest atomic number.

If there are two substituents with equal rank, proceed along the two substituent chains until there is a point of difference. First, determine which of the chains has the first connection to an atom with the highest priority (the highest atomic number). That chain has the higher priority.

If the chains are similar, proceed down the chain, until a point of difference.

If a chain is connected to the same kind of atom twice or three times, check to see if the atom it is connected to has a greater atomic number than any of the atoms that the competing chain is connected to.

• If none of the atoms connected to the competing chain(s) at the same point has a greater atomic number: the chain bonded to the same atom multiple times has the greater priority
• If however, one of the atoms connected to the competing chain has a higher atomic number: that chain has the higher priority.