The key difference between malic acid and maleic acid is that malic acid is a saturated dicarboxylic acid, whereas maleic acid is an unsaturated dicarboxylic acid.
Malic acid and maleic acid are dicarboxylic acids. This means these compounds contain two carboxyl groups (-COOH) in the same molecule, attached to two different carbon atoms. The difference between malic acid and maleic acid lies on the saturation (presence of double or triple bonds means unsaturation). Since maleic acid has a double bond between two carbon atoms, it is an unsaturated compound. But there are no double or triple bonds between carbon atoms of malic acid.
CONTENTS
1. Overview and Key Difference
2. What is Malic Acid
3. What is Maleic Acid
4. Side by Side Comparison – Malic Acid vs Maleic Acid in Tabular Form
5. Summary
What is Malic Acid?
Malic acid is an organic compound having the chemical formula C4H6O5. It falls under the category of dicarboxylic acids because it has two –COOH groups at two terminals. There are two stereoisomers of malic acid: L and D isomers. But only L isomers exist naturally. The preferred IUPAC name of this compound is 2-Hydroxybutanedioic acid. The chemical structure of this compound is as follows:
Figure 01: Malic Acid Chemical Structure
Almost all living organisms can produce this compound in their bodies. The sour taste of some fruits is caused by malic acid. Therefore, it is useful as a food additive. The anion of malic acid is malate anion. Malic acid was isolated for the first time from apple juice. The sourness of unripe apple is due to the presence of malic acid in high concentrations.
Production of malic acid industrially requires a racemic mixture of two stereoisomers of malic acid. We can perform this preparation via hydration of maleic anhydride. Thereafter, we can separate the enantiomers from each other via chiral resolution.
What is Maleic Acid?
Maleic acid is an organic compound having the chemical formula HO2CCH=CHCO2H. It is a dicarboxylic acid which has two carboxyl groups (-COOH groups) attached to two different carbon atoms. Maleic acid is the cis isomer of butenedioic acid whereas fumaric acid is the trans isomer. The molar mass of this compound is 116 g/mol. It appears as a white solid. Furthermore, this compound is less stable compared to fumaric acid, but it is comparatively more water-soluble.
Figure 02: Chemical Structure of Maleic Acid
The properties of maleic acid are determined mainly by intramolecular hydrogen bonding. In the industrial scale, we can produce maleic acid via hydrolysis of maleic anhydride. There are many uses of maleic acid: as raw material for the production of different chemicals such as glyoxylic acid, as an adhesion promoter for different substrates, used in the production of different pharmaceutical drugs, etc.
What is the Difference Between Malic Acid and Maleic Acid?
Malic acid and maleic acid are two different dicarboxylic acids. Malic acid is an organic compound having the chemical formula C4H6O5 while maleic acid is an organic compound having the chemical formula HO2CCH=CHCO2H. The key difference between malic acid and maleic acid is that malic acid is a saturated dicarboxylic acid, whereas maleic acid is an unsaturated dicarboxylic acid.
Malic acid is produced via the hydration of maleic anhydride while the maleic acid is produced from the same compound via hydrolysis. So, this is another difference between malic acid and maleic acid. Besides, the major application of malic acid is as a food additive. There are several important applications of maleic acid, including the production of pharmaceutical drugs, other chemicals etc. whereas maleic acid is used as a raw material.
Summary – Malic Acid vs Maleic Acid
In summary, malic acid and maleic acid are two different dicarboxylic acids. The key difference between malic acid and maleic acid is that malic acid is a saturated dicarboxylic acid whereas maleic acid is an unsaturated dicarboxylic acid.
Reference:
1. “Malic Acid”. Wikipedia.Org, 2019, Available here.
Image Courtesy:
1. “Äpfelsäure3” By NEUROtiker (talk) – Own work (Public Domain) via Commons Wikimedia
2. “Maleinsäure” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia