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Carboxylate ions are good nucleophiles. They react with alkyl halides to form esters. The following reaction shows the reaction mechanism. [1]: 398–9 The S N 2 reaction between sodium acetate and bromoethane. The products are ethyl acetate and sodium bromide.
The intermediate collapses and expels the leaving group (X) to give the substitution product 3. While nucleophilic acyl substitution reactions can be base-catalyzed, the reaction will not occur if the leaving group is a stronger base than the nucleophile (i.e. the leaving group must have a higher pK a than the nucleophile). Unlike acid ...
In another example of asymmetric synthesis the α,β-unsaturated carbonyl compound first reacts with a chiral imidazolidinone catalyst and chiral auxiliary to an iminium compound in an alkylimino-de-oxo-bisubstitution which then reacts enantioselective with the furan nucleophile. The immediate reaction product is a nucleophilic enamine and the ...
A common side-product is produced when the azodicarboxylate displaces the leaving group instead of the desired nucleophile. This happens if the nucleophile is not acidic enough (pK a larger than 13) or is not nucleophilic enough due to steric or electronic constraints. A variation of this reaction utilizing a nitrogen nucleophile is known as a ...
Converting a carboxylic acid to an amide is possible, but not straightforward. Instead of acting as a nucleophile, an amine will react as a base in the presence of a carboxylic acid to give the ammonium carboxylate salt. Heating the salt to above 100 °C will drive off water and lead to the formation of the amide.
The physical manifestation of leaving group ability is the rate at which a reaction takes place. Good leaving groups give fast reactions. By transition state theory, this implies that reactions involving good leaving groups have low activation barriers leading to relatively stable transition states.
Fischer esterification is an acyl substitution reaction based on the electrophilicity of the carbonyl carbon and the nucleophilicity of an alcohol. Carboxylic acids tend to be deprotonated by nucleophiles, which gives an unreactive carboxylate.
A variety of nucleophiles attack, breaking the carbon-oxygen double bond, and leading to addition-elimination reactions. Nucleophilic reactivity is often proportional to the basicity of the nucleophile and as nucleophilicity increases, the stability within a carbonyl compound decreases. [5]