Search results
Results From The WOW.Com Content Network
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.
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]
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).
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 ...
For example, in reacting ethanol with acetic anhydride, ethyl acetate forms and acetic acid is eliminated as a leaving group, which is considerably less reactive than an acid anhydride and will be left as a byproduct (in a wasteful 1:1 ratio with the ester product) if product is collected immediately. If conditions are acidic enough, the acetic ...
The two ester positions can be more smoothly differentiated by incorporating benzyl or tert-butyl groups via the corresponding acetoacetate esters. Benzyl groups can be removed by catalytic hydrogenolysis over palladium on carbon , and tertiary-butyl groups can be removed by treatment with trifluoroacetic acid , or boiling aqueous acetic acid.