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What is Butyric Acid?

Butyric acid, which is known under the systematic name butanoic acid. It is a carboxylic acid having the structural formula CH3CH2CH2CO2H. It is a colorless and oily liquid that is soluble in ethanol, water, and ether. Isobutyric acid (2-methylpropanoic acid) is an isomer. The salts and esters of butyric acid are referred to as butanoates or butyrates. This acid does not occur widely in nature, whereas its esters are widespread. It is said as a common industrial chemical.


Characteristics of Butyric Acid

The IUPAC name of butanoic acid is the Butyric Acid.

IUPAC Name

Butyric acid

Butyric Acid Formula

C4H8O2

Molecular Weight or Molar Mass

88.11 g/mol

Density

960 kg/m³

Boiling Point

163.5 °C

Melting Point

-7.9 °C

Chemical Formula

CH3CH2CH2-COOH


Butyric Acid Structure

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Properties of Butyric Acid

Let us discuss more on the physical and chemical properties of butyric acid below:


Physical Properties

Odor

Unpleasant odor

Covalently-Bonded Unit

1

Appearance

Colorless clear liquid

Heat capacity

298.15 K, 1 atm

Solubility

Miscible in water and ethanol.

Complexity

49.5


Chemical Properties

  • Butanoic acid reacts with the sodium hydroxide and produces sodium salt of butanoic acid, including water and carbon dioxide.

20NaOH + 21C4H8O2 → 20 NaC4H6O + 4CO2 + 34H2O

  • The acid on treatment with water produces ether and acetic acid. The chemical equation for this is given as follows.

H2O + C4H8O2 → CH3COOH + C2H6O


Occurrence

Triglycerides of the butyric acid compose 3-4% of butter. Whenever the butter becomes rancid, then the butyric acid is liberated from the glyceride by the process of hydrolysis, by taking the help of citation. It is one of the fatty acid subgroups, which are called short-chain fatty acids. Butyric acid is also a medium-strong acid, which reacts with bases and affects various metals.


Butyric acid is found in plant oils and animal fat, breast milk, bovine milk, butter, parmesan cheese, and an anaerobic fermentation product (like body odor and vomit, including in the colon). Butyric acid somewhat tastes like butter, and it has an unpleasant odor. 


Mammals having good scent detection abilities, like dogs, can detect it at 10 parts per billion. On the other side, humans can detect it only in concentrations ranging above 10 parts per million. We can use it as a flavoring agent in food manufacturing.


This acid is one of two primary endogenous agonists of human hydroxycarboxylic acid receptor 2 (HCA2), which is a Gi/o-coupled G protein-coupled receptor.


Butyric acid or the fermentation of butyric acid also exists as the ester octyl butyrate in parsnip (Pastinaca sativa) and the ginkgo tree's seed.


Preparation and Isolation of the Butyric Acid

The oxidation of butyraldehyde can industrially prepare butyric acid.


We can separate it from aqueous solutions by saturation with salts like calcium chloride. The calcium salt, chemically represented as - Ca(C4H7O2)2·H2O, is less soluble in hot water than the cold ones.


Butyric Acid Uses

Butyric acid can be used in the preparation of different butyrate esters. It is also used to form CAB (Cellulose Acetate Butyrate), can be used in a wide range of tools, coatings, and parts, and is more resistant to degradation than that of cellulose acetate. However, Cellulose Acetate Butyrate (CAB) can degrade with exposure to moisture and heat, releasing the butyric acid.


The Low-molecular-weighted esters of the butyric acids, such as methyl butyrate, have mostly pleasant aromas or tastes. Consequently, they are used as perfume and food additives. It can be said as an approved food flavoring in the EU FLAVIS database (as a number - 08.005).


The acid has also been used as a fishing bait additive because of its powerful odor. In many of the commercially available flavors used in the carp baits (Cyprinus carpio) add butyric acid as their ester base. However, it is still unclear whether fish are attracted by the butyric acid itself or to the substances present in it. 


However, butyric acid was one of the few organic acids, which is palatable for both bitterling and tench. This substance has also been used as a stink bomb by the Sea Shepherd Conservation Society to disrupt Japanese whaling crews.


Current Status of the Production of Butyric Acid and Future Needs

Butyric acid is produced industrially via a chemical synthesis primarily. This involves butyraldehyde oxidation, obtained from the propylene, derived from crude oil by oxo synthesis. The butyric acid's chemical synthesis is mainly preferred due to its lower production cost and the starting material’s availability. The second method for the preparation of butyric acid is its extraction from butter.


This is possible because its concentration in butter ranges from 2 to 4% but the process involved is expensive and difficult. Thus, it cannot compete with the chemical alternative. A third method is achieved through fermentation. This method is currently more expensive than chemical synthesis; it has garnered more attention because of both a growing consumer desire for natural and organic products, as chemically opposed to synthesized ingredients and a continuous increase in crude oil prices, which is required for the chemical synthesis.

FAQs (Frequently Asked Questions)

1. Explain the Peripheral Effects of Butanoic Acid?

Ans: 


Cancer

Butyrate produces various effects in cancerous and healthy cells, which is called the "butyrate paradox". In particular, butyrate inhibits colonic tumor cells and stimulates the proliferation of healthy colonic epithelial cells. Besides, the signaling mechanism is not well understood. The volatile fatty acids production like butyrate from fermentable fibers can contribute to colon cancer's dietary fiber role.


Some Short-chain fatty acids such as butyric acid are produced by the beneficial colonic bacteria, referred to as probiotics that feed on/or ferment prebiotics, which are the plant products containing dietary fiber.


These fatty acids of short-chain benefit the colonocytes by increasing energy production and can protect against colon cancer by inhibiting cell proliferation.


Some researchers, conversely, have sought to eliminate butyrate and consider it as a potential cancer driver. Studies in mice indicate it drives the transformation of MSH2, the deficient colon epithelial cells.

2. List Some Facts on the Microbial Biosynthesis of Butanoic Acid?

Ans: Butyrate is generated by various fermentation processes performed by the obligatory anaerobic bacteria. In 1861, a French biologist, chemist, and microbiologist named "Louis Pasteur" discovered this fermentation pathway. A few examples of bacteria that form butyrate include Clostridium kluyveri, Clostridium butyricum, and Clostridium pasteurianum.

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