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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 an atom or group. [1] [2] [3] It can be represented generically as: + +
In outer sphere redox reactions no bonds are formed or broken; only an electron transfer (ET) takes place. A quite simple example is the Fe 2+ /Fe 3+ redox reaction, the self exchange reaction which is known to be always occurring in an aqueous solution containing the aquo complexes [Fe(H 2 O) 6] 2+ and [Fe(H 2 O)6] 3+.
The Tafel equation is an equation in electrochemical kinetics relating the rate of an electrochemical reaction to the overpotential. [1] The Tafel equation was first deduced experimentally and was later shown to have a theoretical justification. The equation is named after Swiss chemist Julius Tafel.
The Tafel equation describes the dependence of current for an electrolytic process to overpotential. The exchange current density is the current in the absence of net electrolysis and at zero overpotential. The exchange current can be thought of as a background current to which the net current observed at various overpotentials is normalized.
For most reactions, the rates increase with increased driving force. A second aspect is that the rate of outer sphere electron-transfer depends inversely on the "reorganizational energy." Reorganization energy describes the changes in bond lengths and angles that are required for the oxidant and reductant to switch their oxidation states .
As an example, self-exchange describes the degenerate reaction between permanganate and its one-electron reduced relative manganate: [MnO 4 ] − + [Mn*O 4 ] 2− → [MnO 4 ] 2− + [Mn*O 4 ] − In general, if electron transfer is faster than ligand substitution, the reaction will follow the outer-sphere electron transfer route.
A thermite reaction using iron(III) oxide. The sparks flying outwards are globules of molten iron trailing smoke in their wake. A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. [1]
The two reactions are named according tho their rate law, with S N 1 having a first-order rate law, and S N 2 having a second-order. [2] S N 1 reaction mechanism occurring through two steps. The S N 1 mechanism has two steps. In the first step, the leaving group departs, forming a carbocation (C +). In the second step, the nucleophilic reagent ...