Butyric Acid

General Information (more information on wikipidia)

Species Molecular Weight (g/mol) Density (g/L) Radius (m) Reference
Butyric Acid 88.1051 D R [1]

Butyric acid is a carboxylic acid with structural formula CH3CH2CH2-COOH. It is notably found in rancid butter, parmesan cheese, and vomit, and has an unpleasant odor and acrid taste, with a sweetish aftertaste (similar to ether). Butyric acid can be detected by mammals with good scent detection abilities (e.g., dogs) at 10 ppb, while humans can detect it in concentrations above 10 ppm.
Butyric acid is a fatty acid occurring in the form of esters in animal fats and plant oils. The glyceride of butyric acid makes up 3% to 4% of butter. When butter goes rancid, butyric acid is liberated from the glyceride by hydrolysis leading to the unpleasant odor. It is an important member of the fatty acid sub-group called short chain fatty acids.
Normal butyric acid or fermentation butyric acid is also found as a hexyl ester in the oil of Heracleum giganteum (cow parsnip) and as an octyl ester in parsnip (Pastinaca sativa); it has also been noticed in the fluids of the flesh and in perspiration.
It is ordinarily prepared by the fermentation of sugar or starch, brought about by the addition of putrefying cheese, with calcium carbonate added to neutralize the acids formed in the process. The butyric fermentation of starch is aided by the direct addition of Bacillus subtilis.
Butyric acid is used in the preparation of various butyrate esters. Low-molecular-weight esters of butyric acid, such as methyl butyrate, have mostly pleasant aromas or tastes. As a consequence, they find use as food and perfume additives. They are also used in organic laboratory courses, to teach the Fisher esterification reaction.
The acid is an oily colorless liquid that solidifies at -8 °C; it boils at 164 °C. It is easily soluble in water, ethanol and ether, and is thrown out of its aqueous solution by the addition of calcium chloride. Potassium dichromate and sulfuric acid (also known as sulphuric acid) oxidize it to carbon dioxide and acetic acid, while alkaline potassium permanganate oxidizes it to carbon dioxide. The calcium salt, Ca(C4H7O2)2·H2O, is less soluble in hot water than in cold.

Diffusion of in water:

  • Alone at 25 degrees: $D = 870 \ \mu m^{2} s^{-1}$ [1]

Diffusion of in PBS:

Diffusion of in cellular matrix:

1. Santegoeds, C. M., T. G. Ferdelman, G. Muyzer, and D. de Beer. 1998. Structural and functional dynamics of sulfate-reducing populations in bacterial biofilms. Appl. Environ. Microbiol. 64:3731-3739.
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