Branched Chain Nomenclature

Naming branched chains is a process that requires a lot of attention, especially with regard to the numerical order of carbons in the main chain.
Follow the rules established by the International Union of Pure and Applied Chemistry (IUPAC) for this task:
RULE 1: Determine the main chain (longest sequence of carbon atoms) and its name.
If you need to consult: Alkane nomenclature
RULE 2: Identify the branches and name them.
Nomenclature of branches in: Hydrocarbon branches
RULE 3: Begin numbering the main chain from the end that contains the closest organic group (branch) substituent.
Examples: Correctly name the following branch chains:

RULE 1: The main chain is highlighted and its nomenclature is butane.
RULE 2: The present branch is CH₃ (methyl).
RULE 3: The numbering of the main chain is done from the end that contains the nearest branch, in this case we start from right to left.
The official nomenclature for the above compound is: 2 – methylbutane.
Now a slightly bigger chain!

Determine the main string and its name: the main string matches the

Hexane (linear chain with six carbons), but the presence of the branch gives the compound a new name. Rule 3 says that we must start numbering from the end that contains the closest branch, so the final nomenclature for the compound will be 3 – methyl hexane.
TIP: The end at which the numbering must start is the one where you get the smallest number indicating the positions of the groups. In the case above, if we number the main chain in the other direction (from left to right), we would have 4 - methyl hexane, this form is incorrect, since between digits 3 and 4 we must choose 3 (smallest), obeying the Rule 3.
By Líria Alves
Graduated in Chemistry
Brazil School Team

See more!
Hydrocarbon Branches
Properties of organic compounds

Organic chemistry - Chemistry - Brazil School

Source: Brazil School - https://brasilescola.uol.com.br/quimica/nomenclatura-cadeias-ramificadas.htm