Propanoic acid. Physical and chemical properties. Application, safety at work.
Propanoic acid (other names - methylacetic acid, preservative E280, propionic acid) - a liquid without color with a pungent unpleasant odor. Has the following chemical formula: C2H5-COOH.
Physical properties of propionic acid:
1. The melting point is -21 °.
2. The boiling point is 141 °.
3. The flash point is 54 °.
4. The molar mass is equal to 74.08 g / mol.
5. Under standard conditions, it is a colorless liquid.
6. The autoignition temperature is 440 °.
Chemical properties of propionic acid:
1. Miscible with water (H2O) and organic solvents.
2. Propanoic acid is a typical representative of carboxylic saturated acids. It can form esters, halogenides, amides and other substances.
The history of propanoic acid discovery
This substance was first described in 1844Gottlieb Johan, who found him among the products of decomposition of sugar. Then, for some time, other chemists got this acid in many ways, without realizing that they were getting the same compound. And in 1847 Jean-Baptiste Dumas found that the substances obtained earlier were the same acid, which he later named as propanoic acid, the formula of which is C2H5-COOH.
What are the ways of producing propanoic acid?
In nature propanoic acid is found in oil.
In industry, this substance is producedby carbonylation of ethylene according to the Repepe reaction as a by-product in the oxidation of carbons, catalytic oxidation of propane aldehyde in the presence of manganese or cobalt ions.
Also, a large amount of methylacetic acid can be obtained by the production of acetic acid, however, modern production methods have made this method a secondary source of propanoic acid.
This substance can be obtained by metabolic decomposition of amino acids and fatty acids, which contain an odd number of carbon atoms.
Propanoic acid is also produced by bacteria of the genusPropionibacterium (as the final product of its metabolism). These bacteria are found in the digestive system of ruminants, and it is because of their activity that the Swiss cheese has its own unique flavor.
Propionic acid derivatives
These are ethers and salts.
Alkali-earth and alkali salts are readily soluble in water (H2O), do not dissolve in organic solvents.
The esters of this substance are poorly soluble in (H2O) water, but mixed with organic solvents.
This acid is used in the following cases:
- production of herbicides (for example, dichloroprol,propanol), pharmaceuticals (phenoboline, ibuprofen), certain fragrances (linaloyl-, phenyl-, geranyl-, benzyl-propionates), solvents (butyl-, pentyl-, propylpropionate), plastics (polyvinyl propionate), surfactants (glycol ethers) and vinyl plasticizers;
- because propanoic acid prevents growthsome bacteria and mold, most of it is used as a preservative in food for both humans and animals. In products for animals, propionic acid or its salt (ammonium propionate) is used directly, and in products that are produced for humans, calcium (calcium propionate) or sodium (sodium propionate) or salts is used.
Safety at work
The main hazard when working with propionic acid is chemical burns of varying severity.
In studies that were conducted onlaboratory animals, the only negative effect associated with the long-term consumption of small doses of propanoic acid was the appearance of sores in the esophagus and stomach, which is caused by corrosive properties of the substance. In the course of the experiment it was not found that propanoic acid is mutagenic, carcinogenic, toxic and badly affects the reproductive organs. Getting into the body, the substance we are considering is rapidly oxidized, metabolized and then discharged in the form of carbon dioxide.