Maleic Anhydride: Density & Uses

Instructor: Danielle Reid

Danielle has taught middle school science and has a doctorate degree in Environmental Health

Classified as a type of organic chemical intermediate, maleic anhydride is used to manufacture a variety of products. Continue reading to learn about this compound, its properties, and uses.

Introduction to Maleic Anhydride

The chemical compound maleic anhydride is used in products ranging from pesticide sprays to resin materials. When converted to a different chemical, would you guess that maleic anhydride is used to enhance the flavors of food and beverages? This is certainly true!

A versatile compound, maleic anhydride is an organic chemical classified as the acid anhydride of maleic acid. When we see its molecular structure, we can tell that the molecular formula of maleic anhydride is C4H2O3, and you can see its molecular structure below. If we think back to our early organic chemistry days, we will remember that acid anhydrides are a type of functional group. The structure of this functional group is also shown below.

Molecular Structure of Maleic Anhydride
maleic anhydride

Structure of the Acid Anhydride Functional Group

Do you know where an acid anhydride, like maleic anhydride, is derived from? It is created from a different functional group called a carboxylic acid. The structure of a carboxylic acid is shown below. Let's say you have two carboxylic acid molecules. If you join them together, squishing out the molecule of water between them, the end result is a product called an acid anhydride.

Structure of the Carboxylic Acid Functional Group
carboxylic acid

The exact same process is used to create maleic anhydride from maleic acid. Maleic acid is a dicarboxylic acid. This is a fancy term to say it has two, not one, carboxylic acid functional groups in its structure. When you take maleic acid and squish out the molecule of water via a chemical reaction called dehydration, the product formed is maleic anhydride. This basic equation is shown below.

Synthesis of Maleic Anhydride: Dehydration of Maleic Acid

Properties of Maleic Anhydride

One physical property of maleic anhydride is its color. If you're working with the solid form of this compound, you will notice its white color. You may also be able to smell its highly offensive odor. Most often this odor is described as not only irritating but also choking. With a molecular weight of 98.06g/mol, the melting point of maleic anhydride is 53.58C. Its boiling point is 200.1C. Besides its solubility in water, one last property to make special note of is its density. The density of maleic anhydride is 1.48g/cm3.

Why Is Maleic Anhydride Useful?

There are many uses for maleic anhydride, ranging from a chemical reagent in laboratories to a component in resin products. One particular use that is quite interesting is maleic anhydride's role in the modification of food and beverages. Yes, it sounds very odd to have an acid anhydride in our food and beverages, but it is commonly used as an additive. Specifically, when maleic anhydride is converted to maleic and/or fumaric acid, it is a great preservative or flavor enhancer.

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