Displacement, redox reaction

Give an example of a combination redox reaction, a decomposition redox reaction, and a displacement redox reaction. 

This is an example of direct electron transfer. Zinc gives up two electrons (becomes oxidized) to the Cu ion that accepts the electrons (reducing it to copper metal). In Chapter 8,1 show you that nothing happens if you place a piece of copper metal into a solution containing Zn because zinc gives up electrons more easily than copper. I also show you the activity series of metals that allows you to predict whether or not a displacement (redox) reaction will take place. 

In displacement redox reactions, one element displaces the ion of another from solution. 

Why do decomposition redox reactions typically have compounds as reactants, whereas combination redox and displacement redox reactions have one or more elements ... 

Combination Redox Reactions 136 Decomposition Redox Reactions 137 Displacement Redox Reactions and Activity Series 137... 

When a strip of zinc metal is added to a solution of copper(II) sulfate, the blue color slowly fades, and the zinc metal is replaced by copper metal (Figure 4-13). As copper ions in the solution are reduced to copper metal, zinc atoms are oxidized to Zn cations. This is an example of a metal displacement reaction, in which a metal ion in solution (Cu ) is displaced by another metal (Zn) by means of a redox reaction. Figure 4-13 also shows molecular views of this displacement reaction. 

Displacement reactions are always oxidation-reduction reactions, while metathesis reactions are never redox reactions. 

Depending on the context, oxidation can either refer to (a) a reaction in which oxygen combines chemically with another substance or (b) any reaction in which electrons are transferred. For the latter definition, oxidation and reduction always occur simultaneously (redox reactions), and the substance that gains electrons is termed the oxidizing agent. Electrons might also be displaced within a molecule without being completely transferred away from it. 

Such highly ionized species have been detected for Cl-37 produced by the EC decay of Ar-37 in gaseous phase ((>). In solids, however, such anomalous states are not realized or their life time is much shorter than the half-life of the Mossbauer level (Fe-57 98 ns and Sn-119 17-8 ns) because of fast electron transfer, and usually species in ordinary valence states (2+, 3+ for Fe-57 and 2+, 4+ for Sn-119) are observed in emission Mossbauer spectra (7,8). The distribution of Fe-57 and Sn-119 between the two valence states depends on the physical and chemical environments of the decaying atom in a very complicated way, and detection of the counterparts of the redox reaction is generally very difficult. The recoil energy associated with the EC decays of Co-57 and Sb-119 is estimated to be insufficient to induce displacement of the atom in solids. 

Single displacement (replacement) reactions are reactions in which atoms of an element replace the atoms of another element in a compound. All of these single replacement reactions are redox reactions, since the element (in a zero oxidation state) becomes an ion. Most single displacement reactions can be categorized into one of three types of reaction ... 

Single displacement reactions are redox reactions in which atoms of an element replace the atoms of another element in a compound. 

You have seen that the single displacement reaction of zinc with copper(II) sulfate is a redox reaction, represented by the following chemical equation and net ionic equation. 

In your previous chemistry course, you classified reactions into four main types synthesis, decomposition, single displacement, and double displacement. You also learned to recognize combustion reactions and neutralization reactions. You have now learned to classify redox reactions. In addition, you have also learned about a special type of redox reaction known as a disproportionation reaction. 

Zinc metal reacts spontaneously with an aqueous solution of copper sulfate when they re placed in direct contact. Zinc, being a more reactive metal than copper (it s higher on the activity series of metals presented in Chapter 8), displaces the copper ions in solution. The displaced copper deposits itself as pure copper metal on the surface of the dissolving zinc strip. At first, the reaction may appecir to be a simple single replacement reaction, but it s also a redox reaction. 

Redox potential data frequently correlate with parameters obtained by other spectroscopic measurements. The correlation of E° potentials with gas-phase ionization potentials has already been briefly discussed. Electronic transitions observed by UV-visible spectroscopy involve the promotion of an electron from one orbital to another and this can be viewed as an intramolecular redox reaction. If the promotion involves the displacement of an electron from the HOMO to the LUMO, then the redox potentials for the reduction of the compound, °REd, and for its oxidation, °ox, are of importance. For a closely related series of compounds, trends in oxidation and reduction potentials can be related to shifts in the absorption frequency, v. If the structural perturbation causes the HOMO and the LUMO to rise or fall in energy in tandem, then (E°RED — E°ox) will remain constant in such cases the HOMO—LUMO frequency (energy) will be essentially independent of the structural perturbation. Where there is a differential influence of the perturbation on the HOMO and the LUMO, then ( °red E°ox) will vary as will the energy of the electronic transition. In such cases a linear correlation of °red or E°0x may result. In the limit the energy of the HOMO, or more usually the LUMO, will be unaffected by structural perturbation where the acceptor orbital is pinned, direct linear correlation of E°Gx with v should be apparent. With E°ox and v in a common energy unit, the plot E°0x versus v should have a slope close to one.33-36... 

Not all reactions are redox reactions. Only the ones in which electrons are transferred from one reactant to another are classified as redox reactions. Many single-displacement reactions, combination reactions, decomposition reactions, and combustion reactions are redox reactions. Double displacement reactions never involve the transfer of electrons and are not, therefore, redox reactions. Since acid-base reactions are just a special type of double displacement reaction, they cannot be redox reactions, either. 

Trichloromethylarenes are found to activate the pyridine ring via N-alkylation such that 4-chloropyridines are formed (Scheme 20) <1995TL5075>. In the case of nicotinamide, the dihydropyridine intermediate 121 undergoes an intermolecular redox reaction with hydride transferred to the benzylic position to give 122. Subsequent displacement of the C-4 chloride with nicotinamide affords the bispyridinium salts 123. 

These reactions are part of a larger category of reactions known as redox reactions (redox is short for oxidation-reduction). Sometimes these are called displacement reactions. These are chemical reactions in which atoms of one element replace the atoms of a second element in a compound. A general equation for a single-replacement reaction involving a metal (A), replacing a metallic cation in solution (B) is ... 

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