1911 Encyclopædia Britannica/Valeric Acid
VALERIC ACID, or Valerianic Acid, C4H9CO2H, an organic acid belonging to the fatty acid series, which exists in four isomeric forms, one of which contains an asymmetric carbon atom and consequently occurs in two optically active modifica- tions and one optically inactive modification. Ordinary valeric acid (baldrianic acid) is a mixture of isovaleric acid or isopro-pylaceticacid, (CH3)2 CH-CH2 -CO2H, and optically active methy- lethylacetic acid, (CH3) (C2H5)CH-CO2 H, which occur free or as esters in the vegetable and animal kingdoms, chiefly in the roots of Angelica archangelica and Valeriana officinalis. It may be extracted by boiling with water or soda. A similar product is obtained by oxidizing fermentation amyl alcohol with chromic acid. Isovaleric acid is an oily liquid having the odour of stale cheese and boiling at 174; the salts are usually greasy to the touch. Potassium permanganate oxidizes it to /3-oxyisovaleric acid (CH3)2-C(OH)-CH2-CO2H, whilst nitric acid gives, among other products, dinitropropane, (CH3)2 C(NO2)2. The acid has been synthesized, as has also the inactive form of methylethyl-acetic acid; this modification is split into its optical antipodes by crystallization of its brucine salt. Normal valeric acid or propylacetic acid, CH3-CH2-CH2 -CH2-CO2 H, is a liquid boiling at 186°. The remaining isomer, pivalic or trimethylacetic acid, (CH3)3 C-CO2H, melts at 35° and boils at 163°. Both these acids are synthetic products.