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A single-displacement reaction, also known as single replacement reaction or exchange reaction, is an archaic concept in chemistry. It describes the stoichiometry of some chemical reactions in which one element or ligand is replaced by atom or group. [1] [2] [3] It can be represented generically as:
Coupling reactions are a class of metal-catalyzed reactions involving an organometallic compound RM and an organic halide R′X that together react to form a compound of the type R-R′ with formation of a new carbon–carbon bond. Examples include the Heck reaction, Ullmann reaction, and Wurtz–Fittig reaction. Many variations exist. [3]
The halogens can all react with metals to form metal halides according to the following equation: 2M + nX 2 → 2MX n. where M is the metal, X is the halogen, and MX n is the metal halide. Sample of silver chloride. In practice, this type of reaction may be very exothermic, hence impractical as a preparative technique.
Going from the bottom to the top of the table the metals: increase in reactivity; lose electrons more readily to form positive ions; corrode or tarnish more readily; require more energy (and different methods) to be isolated from their compounds; become stronger reducing agents (electron donors).
For fluorine, chlorine, and bromine, this reaction is in the form of: H 2 + X 2 → 2HX. However, hydrogen iodide and hydrogen astatide can split back into their constituent elements. [15] The hydrogen-halogen reactions get gradually less reactive toward the heavier halogens. A fluorine-hydrogen reaction is explosive even when it is dark and cold.
Halogenation of saturated hydrocarbons is a substitution reaction. The reaction typically involves free radical pathways. The regiochemistry of the halogenation of alkanes is largely determined by the relative weakness of the C–H bonds. This trend is reflected by the faster reaction at tertiary and secondary positions.
An intramolecular S N 2 reaction by the anion forms the cyclic backbone of morphine. [14] Synthesis of morphine using lithium–halogen exchange. Lithium–halogen exchange is a crucial part of Parham cyclization. [15] In this reaction, an aryl halide (usually iodide or bromide) exchanges with organolithium to form a lithiated arene species.
In chemistry, the haloform reaction (also referred to as the Lieben haloform reaction) is a chemical reaction in which a haloform (CHX 3, where X is a halogen) is produced by the exhaustive halogenation of an acetyl group (R−C(=O)CH 3, where R can be either a hydrogen atom, an alkyl or an aryl group), in the presence of a base.