Propanoic acid
- Propanoic acid
- Ethan carboxylic acid
- Metacetonic
- E 280 ( E numbers for food additives )
Colorless liquid with an unpleasant odor
Liquid
0.99 g · cm -3 ( 20 ° C)
-21 ° C.
141 ° C.
4 hPa ( 20 ° C)
4.87
- Miscible with water
- Soluble in ethanol, diethyl ether and chloroform
1386
Risk
-510.7 KJ / mol
Template: Infobox chemical / molecular formula search available
Propionic acid is the trivial name of propionic acid, a carboxylic acid with a pungent odor. Its salts and esters Propionate hot or systematically propanoates.
History and etymology
Johann Gottlieb discovered in 1844 by the reaction of carbohydrates with molten alkali metal hydroxides propionic acid and its salts. The name of propionic acid was given to her in 1847 by the French chemist Jean -Baptiste Dumas. Dumas led him from Greek protos, the first ', and pion, fat ' from, because it is showing a behavior similar to fatty acids by the salting-out an oil film on water and a soap -like the smallest (first) carboxylic acid potassium salt forms.
Occurrence and extraction
Propionic acid is found in nature in some essential oils. It is produced industrially from ethene, carbon monoxide and water. There are also bacteria, which form propionic acid, such as clostridia which colonize the large intestine of man. They form the acid from undigested carbohydrates. In the production of certain cheese is the formation of propionic acid by certain bacteria of significance: propionic in curd form of Emmentaler or other types of hard cheese, the characteristic holes and the flavor by releasing carbon dioxide and propionic acid. It also forms from fermentation and fermentation processes or during the biodegradation of vegetable or animal materials.
A cause of unpleasant mouth odor in humans is - in addition to butyric acid, hydrogen sulfide and other volatile sulfur-containing organic compounds ( methanethiol, dimethyl ) - propionic acid.
In the generation of biogas from organic waste propionic acid is formed. Propionic acid produced in the second phase of the material decomposition of the acid- forming phase, in an air-tight fermentation tanks.
Use
Propionic acid is an important synthetic building block for the production of plastics, herbicides, pharmaceuticals. Propionic acid ( E 280 ) and its salts sodium propionate ( E 281 ), calcium propionate (E 282) and potassium propionate (E 283 ) are used as preservatives. The acid itself has an unpleasant taste for humans, and therefore in the food industry, in particular for packaged sliced bread or pastry, the salts of the acid. The acid itself is often added silage, where the share can be up to 2% of the dry matter. The additive has the positive side effect is that it prevents ketoacidosis in dairy cattle. In the Federal Republic of Germany Propionic acid and its salts was banned from 1988 in sliced bread, because it was reported that she evokes as rats cancer-like changes of the forestomach. According to the latest EU law it is allowed again. Humans need to reduce propionic acid vitamin B12. In addition, propionic acid and its salts are permitted as a preservative in cosmetics under the Cosmetics Ordinance.
Many fungi are able to grow in a position to pure propionic acid. Particularly in combination with other carbon sources such as glucose, but the polyketide synthase and thus the growth of the fungi is inhibited.
The esters of propionic acid are used as fragrances and flavorings, and as a solvent.
Safety
Propionic acid is corrosive, irritant in dilution to skin, eyes, mucous membranes and respiratory tract. Prolonged administration of propionic acid and propionates in the feed of rats in doses from 0.6 to 5 %, these changes of the forestomach ( thickening and inflammation ) cause. This is classified as species-specific for rat reaction, since in other species such as mice and rabbits, no effects were observed.