A hydrogenation reaction is a chemical process where hydrogen gas (H2) is added to an unsaturated compound, typically an alkene or alkyne, to convert it into a saturated compound. This reaction is commonly used in the food industry to convert liquid vegetable oils into solid fats, such as margarine, by increasing the number of hydrogen atoms in the molecular structure. The process usually requires a catalyst, often made from metals like nickel, palladium, or platinum, to facilitate the reaction. Hydrogenation is important in organic chemistry and industrial applications, as it helps modify the properties of various compounds for different uses.