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Transesterification is the process of exchanging the organic functional group R″ of an ester with the organic group R' of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst. [1] Strong acids catalyze the reaction by donating a proton to the carbonyl group, thus making it a more potent electrophile.
Fats react with alcohols (R'OH) instead of with water in hydrolysis in a process called transesterification. Glycerol is produced together with the fatty acid esters. Most typically, the reaction entails the use of methanol (MeOH) to give fatty acid methyl esters: RCO 2 CH 2 –CHO 2 CR–CH 2 O 2 CR + 3 MeOH → 3 RCO 2 Me + HOCH 2 –CHOH ...
The conversion of methyl acetate back into its components, by an acid, is a first-order reaction with respect to the ester. The reaction of methyl acetate and a base, for example sodium hydroxide, is a second-order reaction with respect to both reactants. Methyl acetate is a Lewis base that forms 1:1 adducts with a variety of Lewis acids.
The other method involves transesterification of sucrose and fatty acid methyl ester using sodium methoxide as a basic catalyst. The by-product methanol can be removed via distillation to drive the equilibrium to favor sucrose esters. The process does not work for food industry because DMF is poisonous and may not be used in food production.
One reason for using FAME (fatty acid methyl esters) in biodiesel production, rather than free fatty acids, is to mitigate the potential corrosion they can cause to metals of engines, production facilities, and related infrastructure. While free fatty acids are only mildly acidic, over time they can lead to cumulative corrosion.
The reaction yields a 1:1 mixture of the homologated acid and the corresponding methyl ester. [12] This method can also be used with primary diazoalkanes, to produce secondary α-diazo ketones. However, there are many limitations.
The enzyme protein-glutamate methylesterase (EC 3.1.1.61) catalyzes the reaction . protein L-glutamate O 5-methyl ester + H 2 O protein L-glutamate + methanol. This enzyme is a demethylase, and more specifically it belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds.
Methyl formate, also called methyl methanoate, is the methyl ester of formic acid. The simplest example of a carboxylate ester, it is a colorless liquid with an ethereal odour, high vapor pressure, and low surface tension. It is a precursor to many other compounds of commercial interest. [4]