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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.
The hydrolysis of esters can occur through either acid and base catalyzed mechanisms, both of which proceed through a tetrahedral intermediate. In the base catalyzed mechanism the reactant goes from a neutral species to negatively charged intermediate in the rate determining (slow) step , while in the acid catalyzed mechanism a positively ...
In acid catalysis and base catalysis, a chemical reaction is catalyzed by an acid or a base. By Brønsted–Lowry acid–base theory, the acid is the proton (hydrogen ion, H +) donor and the base is the proton acceptor. Typical reactions catalyzed by proton transfer are esterifications and aldol reactions.
The archetypal reaction is the alkaline hydrolysis of ethyl benzoate (R=R'=H) in a water/ethanol mixture at 30 °C. Measurement of the reaction rate k 0 combined with that of many substituted ethyl benzoates ultimately result in a reaction constant of +2.498. [3] [needs update] [non-primary source needed] Scheme 2. Hydrolysis of benzoic acid esters
Hydrazine is used to convert the ester to an acylhydrazine, which is reacted with nitrous acid to give the acyl azide. Heating the azide in ethanol yields the ethyl carbamate via the Curtius rearrangement. Acid hydrolysis yields the amine from the carbamate and the carboxylic acid from the nitrile simultaneously, giving the product amino acid. [20]
In organic chemistry, an ortho ester is a functional group containing three alkoxy groups attached to one carbon atom, i.e. with the general formula RC(OR') 3. Orthoesters may be considered as products of exhaustive alkylation of unstable orthocarboxylic acids and it is from these that the name 'ortho ester' is derived.
An ester of a carboxylic acid.R stands for any group (typically hydrogen or organyl) and R ′ stands for any 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 ′). [1]
Acid catalyzed acetal formation from the corresponding hemiacetal. Acetals, as already pointed out, are stable tetrahedral intermediates so they can be used as protective groups in organic synthesis. Acetals are stable under basic conditions, so they can be used to protect ketones from a base. The acetal group is hydrolyzed under acidic conditions.