Question

Which is the correct name of the following molecule?

• 4-ethyl-1,3-dimethylheptane
• 3-ethyl-2,2-dimethyloctane
• 2,3,3-trimethyloctane
• 3-ethyl-2,4-dimethylheptane

Answer 1

Concepts and reason

This problem is based on the concept of IUPAC nomenclature. IUPAC stands for international union of pure and applied chemistry. IUPAC has given a nomenclature to name the organic compounds. The IUPAC name consists of three parts: root name, prefix and suffix.

Fundamentals

The three parts of an IUPAC name are root name, prefix and suffix. The longest chain tells the root name. Prefix tells the position and name of the substitutions present on longest chain. Suffix tells the functional group present in the structure.

 

The given structure of the compound is shown below.

The root name is hept.

The longest chain has seven carbon atoms. So, the root name for the given structure is heptane. Select the longest chain such that, the substituents have the lowest numbers.

 

Three substituents are present on the longest chain. They are two methyl groups and one ethyl group.

The prefix is 3-ethyl-2,4-dimethyl.

One methyl group is substituted at C-2 carbon and another methyl group is at the C-4 carbon atom. One ethyl group is substituted at \(C-3\) carbon. So, the prefix is 3 -ethyl-2,4-dimethyl.

The suffix is ane.

The IUPAC name of the given structure is 3-ethyl-2,4-dimethylheptane.

Seven carbon atoms are present in the longest chain and one methyl group is present at C-2 carbon and other is at C-4 and one ethyl group is present at C-3 carbon. Thus, the IUPAC name of the given structure is 3-ethyl-2,4dimethylheptane.