Nucleophilic substitution happens when the reagent is a nucleophile, which means, an atom or molecule with free electrons.
A nucleophile reacts with an aliphatic substrate in a nucleophilic aliphatic substitution reaction. These substitutions can be produced by two different mechanisms: unimolecular nucleophilic substitution (SN1) and bimolecular nucleophilic substitution (SN2). The SN1 mechanism has two steps. In the first step, the leaving group departs, forming a carbocation. In the second step, the nucleophilic reagent attacks the carbocation and forms a sigma bond. This mechanism can result in either inversion or retention of configuration. An SN2 reaction has just one step. The attack of the reagent and the expulsion of the leaving group happen simultaneously. This mechanism always results in inversion of configuration.
When the substrate is an aromatic compound the reaction type is nucleophilic aromatic substitution. Carboxylic acid derivatives react with nucleophiles in nucleophilic acyl substitution. This kind of reaction can be useful in preparing compouds.
Read more about this topic: Substitution Reaction
Other articles related to "nucleophilic substitution, nucleophilic substitutions, nucleophilic, substitution":
... Nucleophilic substitution via the SN1 or SN2 mechanism does not generally occur with vinyl or aryl halides or related compounds ... Under certain conditions nucleophilic substitutions may occur, via other mechanisms such as those described in the nucleophilic aromatic substitution article ... When the substitution occurs at the carbonyl group, the acyl group may undergo nucleophilic acyl substitution ...
... The OH group is not a good leaving group in nucleophilic substitution reactions, so neutral alcohols do not react in such reactions ... R−OH2+, the leaving group (water) is much more stable, and the nucleophilic substitution can take place ... tertiary alkyl halides, where the hydroxyl group is replaced by a chlorine atom by unimolecular nucleophilic substitution ...
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