Merck, 90964-10X1ML, Hydrogen chloride solution

Methanolic HCl (hydrogen chloride in methanol) is particularly useful for preparing methyl esters of volatile (short chain) fatty acids. Fatty acids are esterified by heating them with an anhydrous alcohol (e.g., methanol) in the presence of an acidic catalyst (e.g., HCl) in a sealed vessel at a high temperature for a short time. In the reaction, a fatty acid molecule and an alcohol molecule are joined, with the release of a water molecule. The derivatives can be quickly and easily recovered, quantitatively, from the reaction medium.