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Alkaline hydrolysis of esters is also known as saponification. A base such as sodium hydroxide is required in stochiometric amounts. Unlike acid-catalyzed ester hydrolysis, it is not an equilibrium reaction and proceeds to completion. Hydroxide ion attacks the carbonyl carbon to give a tetrahedral intermediate, which then expels an alkoxide ion.
On heating, the di-ester undergoes thermal decarboxylation, yielding an acetic acid substituted by the appropriate R group. [1] Thus, the malonic ester can be thought of being equivalent to the − CH 2 COOH synthon. The esters chosen are usually the same as the base used, i.e. ethyl esters with sodium ethoxide.
In this case, enolate formation is irreversible, and the aldol product is not formed until the metal alkoxide of the aldol product is protonated in a separate workup step. When an acid catalyst is used, the initial step in the reaction mechanism involves acid-catalyzed tautomerization of the carbonyl compound to the enol.
Pig liver esterase (PLE) is a widely used enzyme for asymmetric ester hydrolysis. Although it was originally used for the desymmetrizing hydrolysis of glutarate esters, [3] PLE also hydrolyzes malonates, cyclic diesters, monoesters, and other substrates. Active site models have been advanced to explain the selectivity of PLE. [4]
Acid–base-catalysed hydrolyses are very common; one example is the hydrolysis of amides or esters. Their hydrolysis occurs when the nucleophile (a nucleus-seeking agent, e.g., water or hydroxyl ion) attacks the carbon of the carbonyl group of the ester or amide. In an aqueous base, hydroxyl ions are better nucleophiles than polar molecules ...
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.
An ester of carboxylic acid. R stands for any group (organic or inorganic) and R′ stands for organyl group. In chemistry, an ester is a compound derived from an acid (organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group (−OH) of that acid is replaced by an organyl group (−R).
The name "Schotten–Baumann reaction conditions" often indicate the use of a two-phase solvent system, consisting of water and an organic solvent. The base within the water phase neutralizes the acid, generated in the reaction, while the starting materials and product remain in the organic phase, often dichloromethane or diethyl ether.