Question

Select the correct name for the following compound, including the correct (E) or (Z) designation where appropriate. (Z)-2,6-dimethyl-5-octene (E)-3,7-dimethyl-3-octene (Z)-3.7-dimethyl-3-octene (E )-2.6-dirnethyl-5-octene

Answer 1

Concepts and reason

The International Union of Pure and Applied Chemistry (IUPAC) is an organization who gave standard rules for the systematic nomenclature of a compound. These rules are used worldwide for naming a compound to avoid duplicate names.

The given compound contains a double bond; therefore, the nomenclature of double bonded chain is determined by following certain rules which are mentioned in the solution.

Fundamentals

An aliphatic hydrocarbon having -C=C- is termed as alkene. For the nomenclature of an alkene, a longest chain containing carbon-carbon double bond is identified. This longest carbon chain gives the root name for the alkene. The suffix “ene” is added to the root with proper numbering.

The longest carbon chain in the given structure is selected and each carbon is numbered in such a way that first carbon of the double bond gets the lowest possible number as shown below

The root name for this carbon chain is “Oct”.

Add the suffix “ene” to the root name derived in the step one and mention the position of double bond by placing the number before the suffix as mentioned below:

Oct-3-ene

Two substituents are present on the longest chain, as shown below by marking it with a circle:

These are methyl groups, therefore, the prefix added to the name is, methyl. As two methyl groups are present, so, “di” is added before methyl as “3,7-dimethyl”.

The stereochemistry of the given compound is mentioned by adding E or Z to the name at the starting. The groups attached on the double bonded carbon atoms are given priorities based on the sequence rule. The group with higher priority is given number 1 and other with 2. The priority numbers are shown below:

As the higher priority groups are on opposite sides, therefore, the configuration of the compound is “E”.

Ans:

The IUPAC name of the given compound is (E)-3,7-dimethyloct-3-ene.