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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 order of reactivity, as shown by the vigour of the reaction with water or the speed at which the metal surface tarnishes in air, appears to be Cs > K > Na > Li > alkaline earth metals, i.e., alkali metals > alkaline earth metals, the same as the reverse order of the (gas-phase) ionization energies.
Another example of a double displacement reaction is the reaction of lead(II) nitrate with potassium iodide to form lead(II) iodide and potassium nitrate: + + Forward and backward reactions According to Le Chatelier's Principle , reactions may proceed in the forward or reverse direction until they end or reach equilibrium .
Immersion coating processes exploit displacement reactions in which the substrate metal is oxidized to soluble ions while ions of the coating metal get reduced and deposited in its place. This process is limited to very thin coatings, since the reaction stops after the substrate has been completely covered.
In the above reaction, zinc metal displaces the copper(II) ion from the copper sulfate solution, thus liberating free copper metal. The reaction is spontaneous and releases 213 kJ per 65 g of zinc. The ionic equation for this reaction is: Zn + Cu 2+ → Zn 2+ + Cu. As two half-reactions, it is seen that the zinc is oxidized: Zn → Zn 2+ + 2 e −
These types of reactions are the major use for aluminium chloride, for example, in the preparation of anthraquinone (used in the dyestuffs industry) from benzene and phosgene. [12] In the general Friedel-Crafts reaction, an acyl chloride or alkyl halide reacts with an aromatic system as shown: [ 14 ]
The following equation is an example, where M represents the given metal: MCO 3 → MO + CO 2. A specific example is that involving calcium carbonate: CaCO 3 → CaO + CO 2. Metal chlorates also decompose when heated. In this type of decomposition reaction, a metal chloride and oxygen gas are the products. Here, again, M represents the metal: