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A hydroxide ion acting as a nucleophile in an S N 2 reaction, converting a haloalkane into an alcohol. In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they ...
When the solvent is also a nucleophile such as dioxane two successive S N 2 reactions take place and the stereochemistry is again retention. With standard S N 1 reaction conditions the reaction outcome is retention via a competing S N i mechanism and not racemization and with pyridine added the result is again inversion .
The nucleophile may be electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged. An example of nucleophilic substitution is the hydrolysis of an alkyl bromide , R-Br under basic conditions, where the attacking nucleophile is hydroxyl ( OH − ) and the leaving group is bromide ( Br − ).
In such reactions, the nucleophile is usually electrically neutral or negatively charged, whereas the substrate is typically neutral or positively charged. An example of nucleophilic substitution is the hydrolysis of an alkyl bromide, R−Br, under basic conditions, where the attacking nucleophile is the base OH − and the leaving group is Br −:
A nucleophilic aromatic substitution (S N Ar) is a substitution reaction in organic chemistry in which the nucleophile displaces a good leaving group, such as a halide, on an aromatic ring. Aromatic rings are usually nucleophilic, but some aromatic compounds do undergo nucleophilic substitution.
If the nucleophile is a neutral molecule (i.e. a solvent) a third step is required to complete the reaction. When the solvent is water, the intermediate is an oxonium ion. This reaction step is fast. Deprotonation: Removal of a proton on the protonated nucleophile by water acting as a base forming the alcohol and a hydronium ion. This reaction ...
Nucleophilic addition reactions of nucleophiles with electrophilic double or triple bond (π bonds) create a new carbon center with two additional single, or σ, bonds. [1] Addition of a nucleophile to carbon–heteroatom double or triple bonds such as >C=O or -C≡N show great variety.
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-catalyzed processes, both the nucleophile and the leaving group exist as anions under basic conditions.