For the three fatty acids given below, (a) classify each as...

For the three fatty acids given below, (a) classify each as saturated or mono-, di-, or polyunsaturated. (b) write a balanced equation for formation of a triglyceride that incorporates all three. (i) arachidonic acid $$ \mathrm{CH}_{3}-\left(\mathrm{CH}_{2}\right)_{4}-\left(\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{2}\right)_{4}-\left(\mathrm{CH}_{2}\right)_{2}-\mathrm{COOH} $$ (ii) nervonic acid <smiles>CCCCC(CC(C)C)CC(OC)C(=O)O</smiles> (iii) myristic acid <smiles>CCC(C)C(=O)O</smiles>

For the three fatty acids given below,
(a) classify each as saturated or mono-, di-, or polyunsaturated.
(b) write a balanced equation for formation of a triglyceride that incorporates all three.
(i) arachidonic acid
$$
\mathrm{CH}_{3}-\left(\mathrm{CH}_{2}\right)_{4}-\left(\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{2}\right)_{4}-\left(\mathrm{CH}_{2}\right)_{2}-\mathrm{COOH}
$$
(ii) nervonic acid
<smiles>CCCCC(CC(C)C)CC(OC)C(=O)O</smiles>
(iii) myristic acid
<smiles>CCC(C)C(=O)O</smiles>

Key Concepts

Balanced Chemical Equations for Esterification

Writing balanced chemical equations for esterification reactions involves accounting for all atoms and ensuring that each reactant and product is correctly represented. This includes the three fatty acids, glycerol, and the water molecules produced. Understanding the stoichiometry of such reactions is critical as it relates to yields, reaction conditions, and the fundamental conservation of mass in chemical processes.

Fatty Acid Saturation

Fatty acid saturation refers to the presence or absence of double bonds in the hydrocarbon chain. A saturated fatty acid contains no double bonds, meaning all carbon atoms are linked by single bonds, whereas unsaturated fatty acids have one or more double bonds. When there is one double bond the acid is classified as monounsaturated; two double bonds indicate a diunsaturated acid, and three or more double bonds indicate a polyunsaturated acid. This classification not only informs the physical properties of the fatty acids, such as melting points, but also their biological roles and nutritional effects.

Triglyceride Formation (Esterification Reaction)

Triglycerides are formed by the esterification reaction between glycerol and three fatty acid molecules. In this reaction, each hydroxyl (–OH) group on the glycerol molecule reacts with the carboxyl (–COOH) group on a fatty acid, releasing a molecule of water for each ester bond formed. This reaction is a condensation reaction and leads to the formation of a triglyceride, a type of lipid that serves as a major form of energy storage in animals.

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