Aldehydes

Introduction:

• Aldehydes are a class of organic compounds.
• They are based on alkane hydrocarbons and are called alkanals.
• Aldehydes are identified by the functional group -CHO.

Functional Group:

• The functional group of aldehydes is -CHO, which is also called the formyl group.

Position of the Functional Group:

• In aldehydes, the -CHO functional group is always found at the end of the carbon chain.
• It occupies the number 1 carbon atom of the chain.

Common Aldehydes:

• Here are some common aldehydes along with their molecular formulas and shortened structural formulas:
• Methanal (Formaldehyde): HCHO (H-CHO)
• Ethanal (Acetaldehyde): CH₃CHO (CH₃-CHO)
• Propanal: C₂H₅CHO (CH₃CH₂CHO)
• Butanal: C₃H₇CHO (CH₃CH₂CH₂CHO or CH₃(CH₂)₂CHO)
• Pentanal: C₄H₉CHO (CH₃(CH₂)₃CHO)
• Hexanal: C₅H₁₁CHO (CH₃(CH₂)₄CHO)
• Heptanal: C₆H₁₃CHO (CH₃(CH₂)₅CHO)
• Octanal: C₇H₁₅CHO (CH₃(CH₂)₆CHO)

Isomerism:

• Isomers of aldehydes can exist by branching the hydrocarbon chain.
• However, the -CHO group is always located at the end of the chain.

Naming Aldehydes:

• When naming aldehydes, the longest carbon chain containing the -CHO functional group is named first.
• The carbon atom in the -CHO group is assigned the number 1.

---

Aldehydes

Example:

• The shortened formula for 5-methylhexanal is CH₃CH(CH₃)(CH₂)₃CHO.
• In this case, the longest chain containing the -CHO group is a hexane chain with a methyl group (CH₃) attached to the fifth carbon atom.