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The Bouveault aldehyde synthesis (also known as the Bouveault reaction) is a one-pot substitution reaction that replaces an alkyl or aryl halide with a formyl group using a N,N-disubstituted formamide. [1] [2] For primary alkyl halides this produces the homologous aldehyde one carbon longer. For aryl halides this produces the corresponding ...
This method produces a precipitate of phthalhydrazide (C 6 H 4 (CO) 2 N 2 H 2) along with the primary amine: C 6 H 4 (CO) 2 NR + N 2 H 4 → C 6 H 4 (CO) 2 N 2 H 2 + RNH 2. Gabriel synthesis generally fails with secondary alkyl halides. The first technique often produces low yields or side products. Separation of phthalhydrazide can be challenging.
Industrial preparation of organolithium reagents is achieved using this method by treating the alkyl chloride with metal lithium containing 0.5–2% sodium. The conversion is highly exothermic. The sodium initiates the radical pathway and increases the rate. [60] The reduction proceeds via a radical pathway.
Furthermore, the reaction is only useful for primary alkyl halides in an intramolecular sense when a 5- or 6-membered ring is formed. For the intermolecular case, the reaction is limited to tertiary alkylating agents, some secondary alkylating agents (ones for which carbocation rearrangement is degenerate), or alkylating agents that yield ...
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.
A positive test is indicated by a change from clear and colourless to turbid, signalling formation of a chloroalkane. [1] Also, the best results for this test are observed in tertiary alcohols, as they form the respective alkyl halides fastest due to higher stability of the intermediate tertiary carbocation.
The Kolbe nitrile synthesis is a method for the preparation of alkyl nitriles by reaction of the corresponding alkyl halide with a metal cyanide. [1] A side product for this reaction is the formation of an isonitrile because the cyanide ion is an ambident nucleophile. The reaction is named after Hermann Kolbe.
Darzens halogenation is the chemical synthesis of alkyl halides from alcohols via the treatment upon reflux of a large excess of thionyl chloride or thionyl bromide (SOX 2) in the presence of a small amount of a nitrogen base, such as a tertiary amine or pyridine or its corresponding hydrochloride or hydrobromide salt.