C4H802 BUTYRIC

ACID  . Two acids are known corresponding to this formula, normal butyric acid, CH3.CH2•CH2•COOH, and isobutyric acid, (CH3)2.CH•COOH . Normal butyric acid or fermentation butyric acid is found in butter, as an hexyl ester in the oil of Heracleum giganteum and as an octyl ester in parsnip (Pastinaca saliva); it has also been noticed in the fluids of the flesh and in perspiration . It may be prepared by the hydrolysis of ethyl acetoacetate, or by passing carbon monoxide over a mixture of sodium acetate and sodium ethylate at 2o5° C . (A . Geuther, Ann., 188o, 2oz,p.306), C2H5ONa+CH3000Na+CO = H•CO2Na+CH3•CH2.CH2•COONa . It is ordinarily prepared by the fermentation of sugar or starch, brought about by the addition of putrefying cheese, calcium carbonate being added to neutralize the acids formed in the process . A . Fitz (Ber., 1878, r1, p . 52) found that the butyric fermentation of starch is aided by the direct addition of Bacillus subtilis . The acid is an oily liquid of unpleasant smell, and solidifies at -19° C.; it boils at 162.3° C., and has a specific gravity of 0.9746 (0° C.) . It is easily soluble in water and alcohol, and is thrown out of its aqueous solution by the addition of calcium chloride .

Potassium bichromate and sulphuric acid oxidize it to carbon dioxide and acetic acid, while alkaline potassium permanganate oxidizes it to carbon dioxide . The calcium salt, Ca(CQH702),.H2O, is less soluble in hot water than in cold . Isobutyric acid is found in the free state in carobs (Ceratonia siliqua) and in the root of Arnica dulcis, and as an ethyl ester in croton oil . It may be artificially prepared by the hydrolysis of isopropylcyanide with alkalies, by the oxidation of isopropyl alcohol with potassium bichromate and sulphuric acid (I . Pierre and E . Puchot, Ann. de chim. et de plays., 1873, [4] 28, p . 366), or by the action of sodium amalgam on methacrylic acid, CH2: C(CH3)•000H . It is a liquid of somewhat unpleasant smell, boiling at 155'5° C . Its specific gravity is 0.9697 (0°°) . Heated with chromic acid solution to 140° C., it gives carbon dioxide and acetone . Alkaline potassium permanganate oxidizes it to a-oxyisobutyric acid, (CH3)2•C(OH).COOH, whilst concentrated nitric acid converts it into dinitroisopropane . Its salts are more soluble in water than those of the normal acid .