Question

When linoleic acid, an unsaturated fatty acid, reacts with hydrogen, it forms a saturated fatty acid. Is linoleic acid oxidized or reduced in the hydrogenation reaction? $$ \mathrm{C}_{18} \mathrm{H}_{32} \mathrm{O}_{2}+2 \mathrm{H}_{2} \longrightarrow \mathrm{C}_{18} \mathrm{H}_{36} \mathrm{O}_{2} $$

Short answer

Linoleic acid is reduced.

Step-by-step solution

Identify reactants and products

Examine the chemical equation: lins= Linoleic acid: C_{18}H_{32}O_{2}, + 2 H_{2} = C_{18}H_{36}O_{2},

Recognize the type of reaction

Notice that hydrogen (H_{2}) is being added to linoleic acid. This reaction is a hydrogenation process.

Determine if oxidation or reduction occurs

In a hydrogenation reaction, hydrogen is added to a molecule. This addition of hydrogen involves the gain of hydrogen atoms, which corresponds to a reduction process (gain of electrons).

Conclusion

Since hydrogen is added to linoleic acid during the reaction, linoleic acid is reduced.

Key concepts

headline of the respective core concept

An unsaturated fatty acid is a type of fat molecule that has one or more double bonds between carbon atoms in its chain. The presence of double bonds means these molecules have fewer hydrogen atoms than saturated fats. For example, linoleic acid, which is mentioned in the exercise, is an unsaturated fatty acid.
These double bonds make unsaturated fats more flexible and give them a liquid form at room temperature. This is why oils made from plants (like olive oil) are usually liquid, whereas animal fats (which are more saturated) are solid.
When we talk about hydrogenation, we're focusing on how these double bonds can be 'broken' by adding hydrogen. This process converts an unsaturated fatty acid into a saturated one, making the previously flexible molecule more rigid. This change can have significant effects on the fat's physical properties and nutritional value.

headline of the respective core concept

Oxidation is a chemical reaction process where a substance loses electrons. Often, oxidation involves the addition of oxygen or the removal of hydrogen from a molecule.
In the context of fatty acids, oxidation can lead to spoilage, causing fats to become rancid. This happens when oxygen in the air reacts with the double bonds of unsaturated fatty acids, breaking them down.
In general, oxidation reactions increase the oxidation state of a molecule, and the molecule becomes more reactive. That's why unsaturated fatty acids, which can be easily oxidized due to their double bonds, are less stable compared to saturated fats.

headline of the respective core concept

Reduction is the opposite of oxidation. It's a chemical reaction where a molecule gains electrons. In organic chemistry, this often means the addition of hydrogen or the loss of oxygen.
In the exercise, linoleic acid undergoes a reduction reaction during hydrogenation. Here, hydrogen is added to the molecule, breaking the double bonds and saturating the fatty acid. As a result, linoleic acid transitions from an unsaturated to a saturated state. This gain of hydrogen (and its associated electrons) is a hallmark of reduction.
Understanding reduction is crucial for comprehending how chemical reactions can change the structure and properties of organic molecules.

headline of the respective core concept

A chemical reaction process describes the transformation of substances through the breaking and forming of chemical bonds. This leads to a change in the composition and properties of the starting materials.
In the case of hydrogenation mentioned in the exercise, the process involves linoleic acid reacting with hydrogen gas. The double bonds in the unsaturated fatty acid break, and hydrogen atoms attach to these points, converting it into a saturated fatty acid.
This type of chemical reaction process is widely used in the food industry to convert liquid vegetable oils into more solid fats, improving shelf life and stability of food products.
Overall, understanding chemical reactions helps us manipulate and create various compounds for practical applications.