Question

Write a chemical equation describing the reaction between glycerol and stearic acid (Table 10.9 ) to give glyceryl tristearate.

Short answer

C3H8O3 + 3C18H36O2 -> C57H110O6 + 3H2O

Step-by-step solution

Identify the Reactants

The two reactants in this reaction are glycerol (C3H8O3) and stearic acid (C18H36O2). Glycerol is a triol, meaning it has three hydroxyl (-OH) groups, and stearic acid is a fatty acid with a long carbon chain and a carboxylic acid group (-COOH).

Understand the General Reaction Type

The reaction between glycerol and stearic acid is an esterification reaction, where each hydroxyl group of glycerol reacts with the carboxyl group of stearic acid to form ester bonds, releasing water (H2O) in the process.

Write the Balanced Chemical Equation

In this reaction, one molecule of glycerol ( ext{C}_3 ext{H}_8 ext{O}_3) reacts with three molecules of stearic acid ( ext{C}_{18} ext{H}_{36} ext{O}_2) to form one molecule of glyceryl tristearate ( ext{C}_{57} ext{H}_{110} ext{O}_6) and three molecules of water. The balanced chemical equation is: \[ ext{C}_3 ext{H}_8 ext{O}_3 + 3 ext{C}_{18} ext{H}_{36} ext{O}_2 ightarrow ext{C}_{57} ext{H}_{110} ext{O}_6 + 3 ext{H}_2 ext{O} \]

Key concepts

Understanding Glycerol

Glycerol, also known scientifically as propane-1,2,3-triol, is a simple polyol compound. In simpler terms, it's an alcohol that contains three hydroxyl (-OH) groups. This makes glycerol a triol, and these hydroxyl groups are key to its reactivity in chemical reactions, like esterification.

Glycerol is a colorless, odorless liquid that has a slightly sweet taste and is non-toxic. It’s well-known for its moisturizing properties, which is why it’s often found in skincare products. But in chemistry, its ability to form bonds with other molecules is more significant.

• The molecular formula for glycerol is \( ext{C}_3 ext{H}_8 ext{O}_3 \).
• It acts as a backbone in reactions with fatty acids, such as the esterification with stearic acid.
• Glycerol’s multiple -OH groups allow it to form multiple ester bonds, facilitating the formation of complex lipids.

Exploring Stearic Acid

Stearic acid is a saturated fatty acid with a long carbon chain. It can be found in various animal and plant fats, and its structure contributes to its utility in various industrial applications.

The structure of stearic acid is quite straightforward - it's composed of a carboxylic acid group (-COOH) attached to a long hydrophobic carbon chain consisting of 18 carbon atoms. This long tail is why stearic acid is considered hydrophobic and tends to repel water.

• The molecular formula of stearic acid is \( ext{C}_{18} ext{H}_{36} ext{O}_2 \).
• Its carboxylic group is reactive and can easily form esters when reacted with molecules like glycerol.
• Due to its long chain, stearic acid provides robustness and stability to the esters it forms, such as glyceryl tristearate.

Creating Glyceryl Tristearate

Glyceryl tristearate, a type of triglyceride, is the product of the esterification reaction between glycerol and stearic acid. This molecule is also commonly known as tristearin and is used in various products for its structural properties.

In the reaction, each hydroxyl group on glycerol bonds with the carboxyl group from three stearic acid molecules, forming three ester linkages and releasing three molecules of water. This process results in the formation of glyceryl tristearate, which is a stable and non-polar compound, making it ideal for use in foods, cosmetics, and pharmaceuticals.

• The chemical structure of glyceryl tristearate is \( ext{C}_{57} ext{H}_{110} ext{O}_6 \).
• It’s solid at room temperature due to the presence of long carbon chains from the stearic acid.
• In industry, it’s prized for its ability to act as a thickening agent and emulsifier.