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The Stobbe condensation entails the reaction of an aldehyde or ketone with an ester of succinic acid to generate alkylidene succinic acid or related derivatives. [1] The reaction consumes one equivalent of metal alkoxide. Commonly, diethylsuccinate is a component of the reaction. The usual product is salt of the half-ester.
Dibasic ester or DBE is an ester of a dicarboxylic acid.Depending on the application, the alcohol may be methanol or higher molecular weight monoalcohols. Mixtures of different methyl dibasic esters are commercially produced from short-chain acids such as adipic acid, glutaric acid, and succinic acid. [1]
Being a diester, diethyl succinate is a particularly versatile building block. It participates in acyloin condensation to give 2-hydroxycyclobutanone. [1] Via condensation with oxalate esters, it serves as a precursor to ketoglutaric acid. [2] It is a reagent in the Stobbe condensation.
The reaction typically employs a strong Lewis acid, such as aluminium chloride as catalyst, to increase the electrophilicity of the alkylating agent. [ 6 ] This reaction suffers from the disadvantage that the product is more nucleophilic than the reactant because alkyl groups are activators for the Friedel–Crafts reaction .
The ensuing reaction results in the cleavage of the ether or the ester into an alkyl iodide and respectively an alcohol or a carboxylic acid. Zeisel determination. By heating this mixture, the gases are allowed to come into contact with a piece of paper higher up the test tube saturated with silver nitrate.
For this reason, the conjugate sodium alkoxide base of the alcohol formed (e.g. sodium ethoxide if ethanol is formed) is often used, since the alkoxide is regenerated. In mixed Claisen condensations, a non-nucleophilic base such as lithium diisopropylamide , or LDA, may be used, since only one compound is enolizable.
A common way to synthesize an NHS-activated acid is to mix NHS with the desired carboxylic acid and a small amount of an organic base in an anhydrous solvent. A coupling reagent such as dicyclohexylcarbodiimide (DCC) or 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) is then added to form a highly reactive activated acid intermediate.
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.