IUPAC Nomenclature – Rules for Selection of Parent Chain In easy way Part 03.

IUPAC Nomenclature – Rules for Selection of Parent Chain In easy way Part 03.

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IUPAC Nomenclature – Rules for Selection of Parent Chain (Easy Way) | Part 03

When naming organic compounds using IUPAC (International Union of Pure and Applied Chemistry) rules, selecting the longest parent chain is the most crucial step. Here’s how you can do it easily:

 Rule 1: Select the Longest Continuous Chain

 The parent chain is the longest continuous carbon chain present in the compound.

Example:
CH₃–CH₂–CH₂–CH₃ (Butane)
CH₃–CH–CH₂–CH₃
   |
  CH₃
Here, the longest chain has 4 carbon atoms, so the parent name is butane.

 Rule 2: Consider the Chain with Maximum Substituents

 If two chains of equal length exist, choose the one with more branches (substituents).

Example:
CH₃–CH₂–CH–CH₃
   |
  CH₃
(Choose the chain with the methyl (-CH₃) group)

 Rule 3: Consider Functional Groups

 If a functional group (like –OH, –COOH, =O, –NH₂) is present, choose the longest chain that includes the functional group.

Example:
CH₃–CH–CH₂–COOH
   |
  CH₃
(The chain must include -COOH (carboxyl group), so the parent chain is butanoic acid).

 Rule 4: Priority Order for Functional Groups

 If multiple functional groups are present, follow this priority order for selecting the chain:
-COOH (Carboxylic acid) > -SO₃H (Sulfonic acid) > -COO- (Ester) > -CHO (Aldehyde) > -C=O (Ketone) > -OH (Alcohol) > -NH₂ (Amine) > Alkene > Alkyne > Alkane

Example:
CH₃–CH₂–CH–OH
   |
  CH₃
(Here, the chain must include -OH, so it is butanol).

 Rule 5: Choose the Chain with Maximum Double or Triple Bonds

 If alkenes (-C=C-) or alkynes (-C≡C-) are present, the parent chain must include the longest sequence of multiple bonds.

Example:
CH₃–CH=CH–CH₃ (But-2-ene)
(Chain must include the double bond)

 Summary: Easy Way to Select the Parent Chain

Longest chain is the parent chain.
More branches (substituents)? Choose that chain.
Functional groups? Always include them.
Double/triple bonds? Always include them.
If tie? Follow functional group priority.

 Do you want practice questions or more examples?

IUPAC Nomenclature – Rules for Selection of Parent Chain In easy way Part 03.

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