Maleic Acid vs. Malic Acid

What's the Difference?

Maleic acid and malic acid are both organic compounds that belong to the carboxylic acid family. However, they differ in their chemical structures and properties. Maleic acid has a cis configuration, meaning that the two carboxylic acid groups are on the same side of the double bond. On the other hand, malic acid has a trans configuration, with the carboxylic acid groups on opposite sides of the double bond. This structural difference leads to variations in their physical and chemical properties. For example, maleic acid is a solid at room temperature, while malic acid is a crystalline powder. Additionally, malic acid is commonly found in fruits and is responsible for their sour taste, while maleic acid is primarily used in the production of resins and polymers.


AttributeMaleic AcidMalic Acid
Chemical FormulaC4H4O4C4H6O5
StructureDouble bond between carbon atomsNo double bond between carbon atoms
IsomerismGeometric isomerismOptical isomerism
AppearanceWhite crystalline solidColorless crystals or white powder
SolubilitySoluble in water and polar solventsSoluble in water and polar solvents
AcidityStronger acidWeaker acid
UsesChemical intermediate, polymer productionFood additive, flavor enhancer

Further Detail


Maleic acid and malic acid are two organic compounds that share similar names and structures, but they have distinct properties and applications. Both acids are dicarboxylic acids, meaning they contain two carboxylic acid functional groups. In this article, we will explore the attributes of maleic acid and malic acid, highlighting their differences and similarities.

Chemical Structure

Maleic acid, also known as cis-butenedioic acid, has the chemical formula C4H4O4. It is a white crystalline solid that is highly soluble in water. The structure of maleic acid consists of a double bond between two carbon atoms and two carboxylic acid groups attached to the adjacent carbon atoms.

On the other hand, malic acid, also known as hydroxybutanedioic acid, has the chemical formula C4H6O5. It is a colorless crystalline solid that is also soluble in water. The structure of malic acid is similar to maleic acid, but it contains an additional hydroxyl group (-OH) attached to one of the carbon atoms.

Physical Properties

Maleic acid has a melting point of 135-139°C and a boiling point of 160-165°C. It is odorless and has a sour taste. Maleic acid is hygroscopic, meaning it readily absorbs moisture from the air. It is also a strong irritant to the skin, eyes, and respiratory system.

Malic acid, on the other hand, has a lower melting point of 100-130°C and a higher boiling point of 260-265°C. It has a slightly fruity odor and a sour taste, similar to maleic acid. Malic acid is non-toxic and is commonly found in many fruits, such as apples, cherries, and grapes, contributing to their tartness.

Chemical Properties

Maleic acid is a relatively strong acid with a pKa value of 1.92. It readily donates a proton from one of its carboxylic acid groups, making it an effective acid catalyst in various chemical reactions. Maleic acid can undergo esterification, oxidation, and addition reactions due to the presence of its double bond.

Malic acid, on the other hand, is a weaker acid with a pKa value of 3.40. It is less acidic compared to maleic acid, but it still exhibits some acidity. Malic acid can undergo decarboxylation, esterification, and reduction reactions. The presence of the hydroxyl group in malic acid also makes it a suitable chelating agent for metal ions.


Maleic acid finds applications in various industries. It is commonly used in the production of resins, polymers, and coatings. Maleic acid is also utilized as a pH regulator in the food industry and as a cleaning agent in household products. Additionally, it is employed in the synthesis of pharmaceuticals and agricultural chemicals.

Malic acid has diverse applications as well. It is widely used as a food additive to enhance the flavor of sour candies, beverages, and fruit-flavored products. Malic acid is also utilized in the cosmetic industry as an ingredient in skincare products due to its exfoliating and moisturizing properties. Furthermore, malic acid is used in the production of biofuels and as a pH adjuster in various industrial processes.

Health Benefits

Maleic acid does not possess any significant health benefits and is primarily used for industrial purposes. However, it is important to handle maleic acid with caution due to its irritant properties.

Malic acid, on the other hand, offers several health benefits. It plays a crucial role in the Krebs cycle, which is involved in the production of energy in the body. Malic acid is also known to improve exercise performance, reduce muscle fatigue, and alleviate symptoms of fibromyalgia. Additionally, it has antioxidant properties that help protect cells from oxidative stress.


In conclusion, maleic acid and malic acid are two distinct organic compounds with different chemical structures, physical properties, and applications. Maleic acid is a stronger acid, commonly used in industrial processes, while malic acid is a weaker acid found naturally in fruits and offers various health benefits. Understanding the attributes of maleic acid and malic acid is essential for their appropriate utilization in different fields.

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