transesterified

Transesterified is an adjective used in chemistry to describe a molecule that has undergone transesterification, the exchange of ester groups between esters and alcohols. In a typical transesterification, an ester reacts with an alcohol to form a different ester and a new alcohol. For example, an ester R1-COOR2 can exchange its alkoxy group with an alcohol R''OH to give R1-COOR'' and R2OH. The reaction is reversible and driven toward completion by removing one of the products or by using excess alcohol.

Catalysis and conditions vary widely. Transesterification can be catalyzed by acids, bases, or enzymes. Base catalysts (such as alkali metal hydroxides or alkoxides) are common for rapid transesterification of triglycerides in biodiesel production, while acid catalysts enable reactions with less reactive alcohols. Enzymatic transesterification, often using lipases, operates under milder conditions and can offer higher selectivity, particularly for sensitive substrates.

Applications and relevance. In biodiesel production, triglycerides from fats or oils are transesterified with methanol or ethanol to yield fatty acid alkyl esters (biodiesel) and glycerol. Transesterified products are also important in polymer chemistry, where transesterification enables exchange reactions between esters within polyesters, aiding polymer modification, recycling, or remodeling of material properties. In organic synthesis, transesterification is a useful method for swapping ester groups to access a range of esters from a common starting material.

In summary, transesterified describes substances that have undergone ester group exchange, a versatile reaction in fuels, polymers, and organic synthesis.