What is Stearic Acid Definition Formula Preparation and Applications
A scientist named Chevreul M.E. initially discovered the Stearic Acid formula (18 carbon atoms) in his fat studies in 1823. Stearic Acid comes after the Grecian term stéar, which means fat (also known as beef fat). It is a long-chain fatty acid (LCFA) with 14 to 18 carbon atoms that is a saturated fatty acid (no C=C double bonds). But, what is Stearic Acid? Stearic Acid is a sticky, whitish substance with a moderate odor that hovers on the surface of liquid naturally. Stearic Acid is found in vegetable and animal fats, with shea butter and cocoa butter being the most common forms. Stearic Acid in cosmetics and plastics, as well as softened plastics and stiffening detergents, are often used. Here you will read about the melting point of Stearic Acid, Stearic Acids in cosmetics, and what is Stearic Acid.
Stearic Acid Formula
As seen in the diagram below, Stearic Acid has an 18-carbon backbone and a straight-chain Stearic Acid structure.
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The above diagram represents the Stearic Acid formula and Stearic Acid structure.
Properties of Stearic Acid Structure
Chemical Formula of Stearic Acid | C18H36O2 |
Molar Mass of Stearic Acid | 284.484 g·mol-1 |
The density of Stearic Acid | 0.9408 g/cm3, at 20°C 0.847 g/cm3, at 70 °C |
The melting point of Stearic Acid | 69.3 °C in 156.7 °F; 342.4 K |
The boiling point of Stearic Acid | Decomposes at 361 °C in 682 °F; 634 K 232 °C In 450 °F; 505 K at 15 mmHg |
Thermal Conductivity | 0.173 W/m·K (70 °C) |
Refractive index (nD) | 1.4299 (80 °C) |
Production of Stearic Acid
It is made of oils and properties of fatty acids by the saponification of triglycerides with heated liquid at a heat of around 100 degrees Celsius. The resulting solution is distilled. The most commonly available octadecanoic acid is a blend of palmitic and Stearic Acids.
Stereophonic acid has more animal fat than vegetable fat in terms of oils and fats. There are a few outliers, such as shea butter and cocoa butter, which contain roughly 28–45 percent Stearic Acid. It possesses the properties of fatty acids. It's also made biosynthetically from carbs, thanks to the fatty acid machinery. In other words, it is a fatty acid example.
Stearic Acid Use
Since Stearic Acid possesses a bifunctional nature, a polar head unit that may be connected to metallic activities, it offers a wide range of applications. Stearic Acid's apolar branch is also soluble and contains organic substances. As a result of this mixture, Stearic Acid is used as a detergent and relaxing ingredient in a variety of applications.
As well as the usage of Stearic Acid in all of such goods is due to the fact that it is reasonably affordable, inactive, and non-toxic. Furthermore, since Stearic Acid undergoes the normal interactions of saturated carboxylic acids, it is also employed in beverages. Because Stearic Acid resists oxidation, metals may be held for a prolonged period.
Here is a list of commodities that require the use of Stearic Acid:
For the pearly effect,
as a food component in detergents in soaps, cosmetics, and cleaners
As a fantastic softening and releasing agent
Like a negative plate additive in lead-acid battery production
Hardening candies in sugar or corn syrup
Gums for chewing
In order to create vitamins and tablets
Candles are made from fatty acid is Stearic Acid.
As an antioxidant coating for aluminum and iron powder.
The above products are all fatty acid examples.
Stearic Acid Safety
Stearic Acid is a saturated fat that is employed in a variety of diets. And, when contrasted to carbohydrates and other saturated fats. Stearic Acid is far better to consume since it decreases LDL (low-density lipoproteins) cholesterol, also known as nasty cholesterol. Stearic Acid has been shown to be safe in several studies. Animal fats are the predominant dietary source of this acid, with botanical fats providing just a minor contribution (Exceptions: coconut, cocoa butter, palm kernel oil ). Similarly, there is no evidence that Stearic Acid consumption causes heart disease and does not affect a person's blood lipid profile during consumption.
Fun Facts
“Although Stearic Acid is utilized in a variety of foods, it is present in nature in diluted levels. However, if Stearic Acid and magnesium combine, magnesium stearate is created, which is toxic and can cause a variety of negative effects if ingested. This chemical molecule is also flammable and heats up freely, causing irritation to the respiratory organs and skin.”
“The melting point of Stearic Acid is so high because it is a saturated fatty acid”.
FAQs on Stearic Acid Structure Properties and Uses in Chemistry
1. What is stearic acid?
**Stearic acid is a saturated long‑chain fatty acid with the molecular formula C18H36O2 and the structure CH3(CH2)16COOH.** It is also known as octadecanoic acid and contains 18 carbon atoms with no carbon–carbon double bonds.
- Belongs to the class of saturated fatty acids
- Contains a carboxylic acid group (–COOH)
- Found naturally in animal fats and some vegetable oils
2. What is the chemical formula and molar mass of stearic acid?
**The chemical formula of stearic acid is C18H36O2 and its molar mass is approximately 284.48 g·mol-1.**
- C: 18 × 12.01 = 216.18 g·mol-1
- H: 36 × 1.008 = 36.29 g·mol-1
- O: 2 × 16.00 = 32.00 g·mol-1
- Total ≈ 284.48 g·mol-1
It is commonly written structurally as CH3(CH2)16COOH.
3. Is stearic acid saturated or unsaturated?
**Stearic acid is a saturated fatty acid because it contains only single carbon–carbon (C–C) bonds.** There are no C=C double bonds in its hydrocarbon chain.
- General formula of saturated fatty acids: CnH2nO2
- Stearic acid fits this pattern with n = 18
- Higher melting point compared to unsaturated fatty acids
4. What is the structural formula of stearic acid?
**The structural formula of stearic acid is CH3(CH2)16COOH.** It consists of a long hydrocarbon chain attached to a terminal carboxyl group.
- CH3– : methyl end
- (CH2)16 : 16 methylene groups
- –COOH : carboxylic acid functional group
Its IUPAC name is octadecanoic acid.
5. How is stearic acid prepared?
**Stearic acid is commonly prepared by the hydrolysis of triglycerides (fats and oils) followed by separation and purification.**
- Triglyceride hydrolysis (example):
C3H5(OOCR)3 + 3H2O → C3H5(OH)3 + 3RCOOH - Produces glycerol and fatty acids (including stearic acid)
- Can also be obtained by hydrogenation of unsaturated fats
This process is widely used in soap and cosmetic industries.
6. What are the physical properties of stearic acid?
**Stearic acid is a white, waxy solid with a melting point of about 69–70°C and is insoluble in water.**
- Physical state: solid at room temperature
- Melting point: ~69–70°C
- Solubility: insoluble in water, soluble in organic solvents
- Nonpolar hydrocarbon chain with a polar –COOH group
Its long saturated chain gives it a relatively high melting point compared to shorter fatty acids.
7. How does stearic acid react with sodium hydroxide?
**Stearic acid reacts with sodium hydroxide in a neutralization reaction to form sodium stearate and water.**
- Balanced equation:
C17H35COOH(aq) + NaOH(aq) → C17H35COONa(aq) + H2O(l) - Product sodium stearate is a soap
- This reaction is an example of acid–base neutralization
8. What is the difference between stearic acid and oleic acid?
**The main difference between stearic acid and oleic acid is that stearic acid is saturated, while oleic acid contains one double bond (unsaturated).**
- Stearic acid: C18H36O2, no C=C bonds
- Oleic acid: C18H34O2, one C=C double bond
- Oleic acid has a lower melting point due to the double bond
This structural difference affects their physical properties and biological behavior.
9. Why is stearic acid used in soap and cosmetics?
**Stearic acid is used in soap and cosmetics because it forms stable soaps and acts as an emulsifier and thickening agent.**
- Forms sodium stearate and potassium stearate in soap making
- Provides hardness and texture to soaps
- Acts as an emulsifying agent in creams and lotions
Its long hydrophobic chain and polar head allow it to stabilize oil–water mixtures.
10. Is stearic acid a strong or weak acid?
**Stearic acid is a weak organic acid because it only partially ionizes in aqueous solution.**
- Contains a carboxylic acid (–COOH) group
- Typical pKa ≈ 4.7–5
- In water: C17H35COOH ⇌ C17H35COO- + H+
Like other fatty acids, it does not completely dissociate, so it is classified as a weak acid.
