It converts carboxylic acids into their methyl esters. The catalysts also contain organic modifiers, either aromatic acid esters and diesters or ethers. These include fusel oil, methanol, aldehydes, organic acids and esters. Glycerol is produced together with the fatty acid esters. The solubilities of amides and esters are roughly comparable. They are soluble in esters, ketones, and ethylene dichloride. In organic chemistry the group is present in nitrous acid esters and nitro compounds. Butyric acid is used in the preparation of various butyrate esters. Cholinesterases are enzymes that facilitate hydrolysis of the esters of choline. Lanolin primarily consists of sterol esters instead. They are various esters of cyanoacrylic acid. Flavorings may contain menthol, sugars, esters, and pyrazines. They are the toxin helenalin and their fatty esters. This oil is a mixture of triglycerides and wax esters. AChE is a hydrolase that hydrolyzes choline esters.