Methylesters

Methyl esters are a class of esters formed when methanol reacts with carboxylic acids. In general, they have the structure R-COO-CH3, where the acyl group comes from the carboxylic acid and the alkoxy group is a methyl group derived from methanol. They occur widely in chemistry, biology, and industry, and include both simple synthetic esters and natural products.

Most methyl esters are prepared by either Fischer esterification of a carboxylic acid with methanol under acid catalysis or by transesterification of another ester with methanol. A prominent industrial example is the production of fatty acid methyl esters (FAME) from fats and oils via transesterification with methanol, typically using basic catalysts. FAMEs are commercially important as biodiesel, offering a renewable substitute for conventionally produced diesel fuel. Methyl esters also serve as solvents, plasticizers, and intermediates in organic synthesis, and many have fragrance or flavor roles in natural products such as methyl salicylate (oil of wintergreen) and methyl cinnamate.

Reactivity and stability: methyl esters can be hydrolyzed back to the parent carboxylic acids and methanol under acidic or basic conditions, and they can undergo further transesterification to form other esters. In practice, many methyl esters are stable enough for use as solvents or intermediates, but their properties vary with the substituents on the acyl group.

Safety and environment: methyl esters are generally biodegradable and less toxic than methanol, though methanol is often used in their production and is hazardous. Biodiesel derived from FAMEs can contain glycerol as a byproduct and impurities that influence performance and emissions.