What is the General Formula of a Fatty Acid?

The general formula for a fatty acid is CH₃(CH₂)_nCOOH, where 'n' typically ranges from 2 to 28 and is always an even number.

Understanding the Fatty Acid Formula

This formula represents a long hydrocarbon chain (the CH₃(CH₂)_n part) ending with a carboxyl group (-COOH). The hydrocarbon chain's length varies, influencing the fatty acid's properties. The even number of carbons arises from the biosynthetic pathway of fatty acid formation.

• CH₃: This represents the methyl group at the end of the hydrocarbon chain.
• (CH₂)_n: This signifies a repeating sequence of methylene groups forming the alkyl chain. The subscript 'n' denotes the number of these repeating units and dictates the fatty acid's length.
• COOH: This is the carboxyl group, which is characteristic of all carboxylic acids and gives fatty acids their acidic properties.

Several sources confirm this general formula:

• Biology LibreTexts: States that fatty acids have the general formula CH₃(CH₂)_nCOOH. (https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/IntroductoryBiology(CK-12)/01%3A_Introduction_to_Biology/1.11%3A_Lipids)
• Chemistry LibreTexts: Describes fatty acids as having a long carbon chain (12 to 24 carbons) with a carboxyl group. (https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Chemistry_for_AlliedHealth(Soult)/14%3A_Biological_Molecules/14.02%3A_Lipids_and_Triglycerides)
• Multiple other sources across websites and educational materials corroborate this fundamental structural formula.

Note: This formula represents saturated fatty acids. Unsaturated fatty acids contain one or more double bonds within the hydrocarbon chain, altering the formula slightly.