How Does Succinic Acid Play a Role in Biochemistry and Industry?
Succinic acid is a dicarboxylic acid. The chemical formula of this acid contains four carbon atoms, six hydrogen atoms, and four oxygen atoms, it is (CH2)2(CO2H)2. Its name is derived from the Latin word “succinum” which means amber. Succinic acid is also known by the name of amber acid as it was first obtained from amber through the distillation method. This dicarboxylic acid takes the form of an anion (succinate ion) in living organisms that possess multiple biological roles. It is also used in the food industry and marketed as food additive E363. It is generated via the tricarboxylic acid cycle (TCA) in mitochondria.
Properties of Succinic Acid
Some of the physical and chemical properties of succinic acid are given below.
Succinic acid is very acidic in taste, appearance in white, and an odorless solid.
Succinic Acid is a four-carbon dicarboxylic acid. The succinic acid formula (molecular formula) is C4H6O4.
Succinic acid molecular weight is 118.09 g/mol.
The succinic acid melting point is 184oC.
Succinic acid readily ionizes In an aqueous solution to form its conjugate base, called succinate.
As a diprotic acid (acid contains at least two hydrogen atoms in its molecule that are able to be released or ionized in water) it undergoes two successive deprotonation reactions that are given below.
(CH2)2(CO2H)2 → (CH2)2(CO2H)(CO2)- + H+
(CH2)2(CO2H)(CO2)- → (CH2)2(CO2)22- + H+
The acid dissociation constant of the above two processes is 4.3 and 5.6, respectively. Both anions formed after deprotonation reactions are colorless and can be isolated as salts, for example, their sodium salt would be, Na(CH2)2(CO2H)(CO2) and Na2(CH2)2(CO2)2.
It is called a succinyl group as a radical group.
Similar to the most simple mono- and dicarboxylic acids, it is not harmful but can be an irritating substance for skin and eyes.
It is a polar substance hence it is easily soluble in water, with the solubility at 25 oC 1g/13ml at.
In some organic solvents, it is soluble such as in ethanol (5.4g/100ml) and glycerol (5.0g/100ml) but it is not soluble in ether and petroleum ether.
How is Succinic Acid made?
There are two common manufacturing processes currently in practice for its production. The first one is the traditional chemical synthesis from petroleum-derived raw materials and another is biological-based fermentation from carbohydrates. These processes are mentioned below.
Chemical Synthesis
In the commercially chemical synthesis process, succinic acid is obtained from maleic anhydride, obtained by oxidation of n-butane or butadiene. There are two major steps in the chemical synthesis process: First maleic anhydride is catalytic hydrogenated to succinic anhydride and later it reacts with water to form succinic acid. Succinic acid can also prepare fumaric acid hydrogenation.
The following reaction is involved in the production of succinic acid by chemical synthesis.
(Image Will be Updated Soon)
Bio-based Fermentation
In the year 2014, there was a brief manufacturing process that was based on fermentation used by the manufacturer BioAmber. A gene-modified Pichia sp. strain of Saccharomycetaceae yeast and biomass as the substrate was used for the production of succinic acid.
Succinic acid is produced by many microorganisms as an intermediate of several biochemical reactions. In ethanol fermentation succinic acid is one of the metabolic co-products. This fermentation is done by the yeast Saccharomyces cerevisiae in addition to lactic acid, glycerol and acetic acid.
Succinic Acid Structure
Succinic acid is dicarboxylic acid which is formed from the formal oxidation of each of the terminal methyl groups of butane to the corresponding carboxy group. Butanedioic acid is its IUPAC name. In the citric acid cycle, it is formed as an intermediate metabolite. This process is both expensive as well as harmful to the environment.
The two active methylene groups of succinic acid can be used for the preparation of a lot of complex organic compounds for their reaction characteristics of esterification, halogenation, sulphonation, dehydration, acylation, oxidation, reduction, etc.
(Image Will be Updated Soon)
Succinic Acid Uses
Some of the important uses of succinic acid are given below.
This acid is used in a variety of industries such as in the cloth industry in polymers for making clothing fibers, the food industry, surfactants and detergents, flavors, and fragrances.
It is used for the preparation of a number of important chemicals such as 2-pyrrolidinone, adipic acid, succinate salts, N-methyl pyrrolidinone, 1,4-butanediol, gamma-butyrolactone, maleic anhydride, tetrahydrofuran, etc.
Succinic acid has many uses in the pharmaceutical industry. It is an active pharmaceutical ingredient (APIs). It is used as an additive in formulation, succinic acid monoethyl ester (an insulinotropic agent), and a crosslinker in drug control release polymers.
This chemical plays an important role in the Krebs cycle (intermediary metabolism) in the body. The Krebs cycle is also known as the citric acid cycle which is a sequence process of enzymatic reaction.
Do you know?
In 1546, through dry distillation (heating in vacuum) of amber, Succinic acid was discovered by Agricola.
Conclusion
Succinic acid is a colorless crystalline solid having a melting point of 184°C. The succinic acid formula is (CH2)2(CO2H)2. It slightly dissolves in some organic substances such as glycerine, ether, acetone, ethanol and is also soluble in water. It does not dissolve in some organic substances such as carbon sulphide, benzene, carbon tetrachloride, or oil. We also see the wide range of applications of succinic acid in different industries.FAQs on Succinic Acid: Structure, Properties, and Applications
1. What is succinic acid and what is its IUPAC name?
Succinic acid is an aliphatic dicarboxylic acid, which means it has two carboxyl functional groups (-COOH). It appears as a white, odourless, crystalline solid. Its chemical formula is C₄H₆O₄. According to the International Union of Pure and Applied Chemistry (IUPAC) nomenclature, succinic acid is officially named butanedioic acid.
2. What are the key physical and chemical properties of succinic acid?
Succinic acid exhibits several distinct properties rooted in its structure. Key properties include:
- Appearance: It is a white, crystalline solid at room temperature.
- Solubility: It is soluble in water, ethanol, and acetone but has low solubility in non-polar solvents like benzene and hexane.
- Melting Point: It has a relatively high melting point of around 185-187 °C, which is due to strong intermolecular hydrogen bonding between its molecules.
- Acidity: As a diprotic acid, it donates two protons in successive steps. The pKa values for these dissociations are approximately 4.2 and 5.6, respectively.
- Reactivity: It undergoes typical reactions of carboxylic acids, such as esterification, amide formation, and reduction. Upon heating, it can lose a water molecule to form succinic anhydride.
3. What are the main industrial and commercial applications of succinic acid?
Succinic acid is a versatile chemical with a wide range of applications across various industries. Some of the most important uses include:
- Polymers and Resins: It serves as a precursor for producing certain polyesters like Polybutylene Succinate (PBS), a biodegradable polymer, and alkyd resins used in paints and coatings.
- Food and Beverage Industry: Under the additive number E363, it is used as an acidity regulator and flavouring agent, contributing a slightly sour and astringent taste.
- Pharmaceuticals: It is used as an excipient (inactive ingredient) to control acidity. It also forms salts (succinates) with active pharmaceutical ingredients, such as in metoprolol succinate and sumatriptan succinate, to improve their stability or absorption.
- Chemical Intermediate: It is a key starting material for the synthesis of other important chemicals like 1,4-butanediol (BDO), tetrahydrofuran (THF), and gamma-butyrolactone (GBL).
4. Where is succinic acid found naturally?
Succinic acid is a naturally occurring substance found in almost all plant and animal tissues. Its natural presence is significant because it is an essential component of the citric acid cycle (or Krebs cycle), a central metabolic pathway for energy production in cells. Notable natural sources include amber (where it's found in concentrations of 3-8%), broccoli, beets, rhubarb, asparagus, and fermented products like cheese and sauerkraut.
5. Why is succinic acid classified as a dicarboxylic acid, and how does this structure influence its properties?
Succinic acid is classified as a dicarboxylic acid because its structure, HOOC-(CH₂)₂-COOH, contains two carboxyl (-COOH) functional groups. This dual-group structure is the primary reason for its unique properties:
- Higher Acidity: Having two acidic groups makes it a diprotic acid, capable of donating two protons (H⁺ ions) in aqueous solutions, unlike monocarboxylic acids like acetic acid.
- Increased Polarity and Melting Point: The two carboxyl groups allow for extensive intermolecular hydrogen bonding. This strong attraction between molecules requires more energy to break, resulting in its solid state at room temperature and a higher melting point compared to a monocarboxylic acid of similar molecular weight.
- Reactivity at Both Ends: The presence of two reactive sites allows it to act as a monomer in condensation polymerisation to form long-chain polyesters like PBS.
6. What is the significance of succinate in the Krebs cycle?
In biological systems, succinic acid exists in its deprotonated form, succinate. Succinate is a crucial intermediate in the Krebs cycle (citric acid cycle), which occurs in the mitochondria of cells. In a key step of the cycle, succinate is oxidized to fumarate by the enzyme succinate dehydrogenase. This reaction is unique because the enzyme is bound to the inner mitochondrial membrane and is part of the electron transport chain (as Complex II). The electrons removed from succinate are passed directly into the electron transport chain to generate ATP, making this step a vital link between the Krebs cycle and cellular respiration's main energy-producing process.
7. How does succinic acid compare to other dicarboxylic acids like adipic acid?
Succinic acid and adipic acid are both dicarboxylic acids, but they differ in the length of the carbon chain separating their two carboxyl groups.
- Structure: Succinic acid (butanedioic acid) has a 4-carbon chain (HOOC-CH₂-CH₂-COOH), while adipic acid (hexanedioic acid) has a 6-carbon chain (HOOC-(CH₂)₄-COOH).
- Solubility: Due to its shorter carbon chain, succinic acid is more polar and thus significantly more soluble in water than adipic acid. As the non-polar hydrocarbon part of the molecule increases in length, water solubility decreases.
- Application in Polymers: This difference in chain length leads to different properties in the polymers they form. For example, adipic acid is a key monomer for the production of Nylon 6,6, a major commercial polyamide, whereas succinic acid is used for polymers like PBS.
