20. The Variety of Organic         Compounds   Previous PageNext Page
        Carboxylic Acids

Long-chain carboxylic acids, with 10 to 20 carbons, are called fatty acids because they are obtained from fats. They are all insoluble in water and form monolayers at air-water interfaces, as do high-molecular-weight alcohols, with their carboxyl groups in the water and their hydrocarbon tails exposed to air. Five of the most important fatty acids in living organisms are shown above. Saturated fatty acids, such as palmitic and stearic, have no double bonds in their hydrcarbon chains; unsaturated fatty


acids such as oleic and palmitoleic, have one double bond; polyunsaturated acids have two or more double bonds.

Carboxylic acids are neutralized by bases, and form salts with them just as inorganic acids do:

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