Final answer:
Chemical reactions unique to unsaturated fatty acids include hydrogenation, where hydrogen is added to double bonds to make them single bonds, and isomerization, which alters the structure without changing the formula.
Step-by-step explanation:
Unsaturated fatty acids contain one or more double bonds between carbon atoms in their hydrocarbon chain. This results in the chain having "kinks" or bends, preventing the molecules from packing tightly together and making them liquids at room temperature.
A common type of chemical reaction that can be observed with unsaturated fatty acids and not with saturated fatty acids, which lack double bonds, is called hydrogenation. In hydrogenation, these double bonds can be converted to single bonds by adding hydrogen atoms. This is done either completely, to turn an oil into a solid fat, or partially, which can sometimes produce undesirable trans fats.
For example, oleic acid, an unsaturated fatty acid, can undergo hydrogenation:
Oleic acid (unsaturated) + Hydrogen → Stearic acid (saturated)
In addition to hydrogenation, unsaturated fatty acids can also undergo reactions such as isomerization, where the structure of the molecule changes (cis-to-trans formation) without the molecular formula changing, and oxidation reactions, which are not as common in saturated fatty acids due to the lack of double bonds.