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The reaction involves a carbocation intermediate and is commonly seen in reactions of secondary or tertiary alkyl halides under strongly basic conditions or, under strongly acidic conditions, with secondary or tertiary alcohols. With primary and secondary alkyl halides, the alternative S N 2 reaction occurs.
Secondary halides are far less reactive. Vinyl, aryl and tertiary alkyl halides are unreactive; as a result, the reaction of NaI in acetone can be used as a qualitative test to determine which of the aforementioned classes an unknown alkyl halide belongs to, with the exception of alkyl iodides, as they yield the same product upon substitution.
The examples in textbooks of secondary substrates going by the S N 1 mechanism invariably involve the use of bromide (or other good nucleophile) as the leaving group have confused the understanding of alkyl nucleophilic substitution reactions at secondary carbons for 80 years [3].
Nucleophilic aromatic substitution. A nucleophilic aromatic substitution (SNAr) 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.
Allylic shifts occur because the transition state is an allyl intermediate. In other respects they are similar to classical nucleophilic substitution, and admit both bimolecular and monomolecular mechanisms (respectively the SN2' and SN1'/SNi' substitutions).
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−). Nucleophilic substitution reactions are common in organic chemistry. Nucleophiles often attack a saturated aliphatic carbon.
Williamson ether synthesis. The Williamson ether synthesis is an organic reaction, forming an ether from an organohalide and a deprotonated alcohol (alkoxide). This reaction was developed by Alexander Williamson in 1850. [2] Typically it involves the reaction of an alkoxide ion with a primary alkyl halide via an S N 2 reaction.
Alkylation occurs when the nucleophilic enolate ion reacts with the electrophilic alkyl halide in an SN 2 reaction and displaces the leaving group by backside attack. Alkylation reactions are subject to the same constraints that affect all SN 2 reactions.