Displacement reaction oxidation-reduction

Classification of Solvents. Solvent classification helps to identify properties useful in solvent selection for individual applications for example, the study of acid-base reactions, oxidation-reduction reactions, inorganic coordination chemistry, organic nucleophilic displacement reactions, and electrochemistry. 

Oxidation-reduction reactions are reactions involving a transfer of electrons from one species to another or a change in the oxidation number of atoms. The concept of oxidation numbers helps us describe this t)q)e of reaction. The atom that increases in oxidation number is said to undergo oxidation the atom that decreases in oxidation number is said to undergo reduction. Oxidation and reduction must occur together in a reaction. Many oxidation—reduction reactions fall into the following categories combination reactions, decomposition reactions, displacement reactions, and combustion reactions. Oxidation—reduction reactions can be balanced by the halfreaction method. 

Seven chemical reactions were identified from the chemistry syllabus. These chemical reactions were selected because they were frequently encountered during the 2-year chemistiy course and based on their importance in understanding concepts associated with three topics, namely, acids, bases and salts, metal reactivity series and inorganic chemistry qualitative analysis. The seven types of chemical reactions were combustion of reactive metals in air, chemical reactions between dilute acids and reactive metals, neutralisation reactions between strong acids and strong alkalis, neutralisation reactions between dilute acids and metal oxides, chemical reactions between dilute acids and metal carbonates, ionic precipitation reactions and metal ion displacement reactions. Although two of the chemical reactions involved oxidation and reduction, it was decided not to include the concept of redox in this study as students had only recently been introduced to ion-electron... 

Many other metal displacement reactions can be visualized, but not all of them occur. Some metals are oxidized readily, but others are highly resistant to oxidation. Likewise, some metal cations are highly susceptible to reduction, but others resist reduction. Zinc displaces copper ions from aqueous solutions, but copper will not replace zinc ions, because Cu is easier to reduce than Zn . Zinc will not displace ions, because... 

When you place a piece of zinc metal into a solution of CuS04, you expect a chemical reaction because the more active zinc displaces the less active copper from its compound (Sec. 7.3). We learned in Chap. 13 that this is an oxidation-reduction reaction, involving transfer of electrons from the zinc to the copper. 

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

A (a) This is a metathesis or double displacement reaction. Elements do not change oxidation states during this reaction. It is not an oxidation-reduction reaction. 

You already know that some metals are more reactive than others. You may also have carried out an investigation on the metal activity series in a previous course. In Investigation 10-A, located on page 470, you will discover how this series is related to oxidation and reduction. You will write chemical equations, ionic equations, and half-reactions for the single displacement reactions of several metals. 

The preparation of novel phase transfer catalysts and their application in solving synthetic problems are well documented(l). Compounds such as quaternary ammonium and phosphonium salts, phosphoramides, crown ethers, cryptands, and open-chain polyethers promote a variety of anionic reactions. These include alkylations(2), carbene reactions (3), ylide reactions(4), epoxidations(S), polymerizations(6), reductions(7), oxidations(8), eliminations(9), and displacement reactions(10) to name only a few. The unique activity of a particular catalyst rests in its ability to transport the ion across a phase boundary. This boundary is normally one which separates two immiscible liquids in a biphasic liquid-liquid reaction system. 

This is obtained via combination of the two partial electrode reactions, oxidation and reduction, reaction (9.5) and (9.6), respectively. Thus, in the displacement deposition of Cu on a Zn substrate, a layer of metallic Cu is deposited on the zinc while Zn dissolves into solution (Fig. 5.11). We stated that this reaction is possible since the Zn/Zn system has an electrode potential lower than that of the Cu/Cu system (Table 5.1 and Fig. 5.10). The overall displacement deposition reaction according to Eq. (9.7) can be considered as the reaction of the electrochemical cell... 

In the first step of the conversion catalyzed by pyruvate decarboxylase, a carbon atom from thiamine pyrophosphate adds to the carbonyl carbon of pyruvate. Decarboxylation produces the key reactive intermediate, hydroxyethyl thiamine pyrophosphate (HETPP). As shown in figure 13.5, the ionized ylid form of HETPP is resonance-stabilized by the existence of a form without charge separation. The next enzyme, dihydrolipoyltransacetylase, catalyzes the transfer of the two-carbon moiety to lipoic acid. A nucleophilic attack by HETPP on the sulfur atom attached to carbon 8 of oxidized lipoic acid displaces the electrons of the disulfide bond to the sulfur atom attached to carbon 6. The sulfur then picks up a proton from the environment as shown in figure 13.5. This simple displacement reaction is also an oxidation-reduction reaction, in which the attacking carbon atom is oxidized from the aldehyde level in HETPP to the carboxyl level in the lipoic acid derivative. The oxidized (disulfide) form of lipoic acid is converted to the reduced (mer-capto) form. The fact that the two-carbon moiety has become an acyl group is shown more clearly after dissocia-... 

Pyrimidine, l-alkyl-2-methyltetrahydro-C-thioacylation, 4, 807 Pyrimidine, 4-alkylsulfinyl-nucleophilic displacement reactions, 3, 97 Pyrimidine, 6-alkylsulfinyl-nucleophilic displacement reactions, 3, 97 Pyrimidine, 2-alkylsulfonyl-nucleophilic displacement reactions, 3, 97 Pyrimidine, 4-alkylsulfonyl-nucleophilic displacement reactions, 3, 97 Pyrimidine, 6-alkylsulfonyl-nucleophilic displacement reactions, 3, 97 Pyrimidine, alkylthio-dealkylation, 3, 95 desulfurization, 3, 95 oxidation, 3, 96 synthesis, 3, 135, 136 Pyrimidine, 2-alkylthio-aminolysis, 3, 96 hydrolysis, 3, 95 Principal Synthesis, 3, 136 Pyrimidine, 4-alkylthio-aminolysis, 3, 96 hydrolysis, 3, 95 Pyrimidine, 6-alkylthio-aminolysis, 3, 96 hydrolysis, 3, 95 Pyrimidine, 4-allenyloxy-rearrangement, 3, 93 Pyrimidine, 4-allyloxy-2-phenyl-rearrangement, 3, 93 Pyrimidine, 4-allynyIoxy-rearrangement, 3, 93 Pyrimidine, 4-anilino-2,5,6-trifluoro-19F NMR, 3, 63 Pyrimidine, 2-aryl-pyrroleacetic acid from, 4, 152 Pyrimidine, arylazo-synthesis, 3, 131 Pyrimidine, 4-arylazo-reduction, 3, 88... 

Cyclic sulfites (68) also are opened by nucleophiles, although they are less reactive than cyclic sulfates and require higher reaction temperatures for the opening reaction. Cyclic sulfite 77, in which the hydroxamic ester is too labile to withstand ruthenium tetroxide oxidation of the sulfite, is opened to 78 in 76% yield by reaction with lithium azide in hot DMF [82], Cyclic sulfite 79 is opened with nucleophiles such as azide ion [83] or bromide ion [84], by using elevated temperatures in polar aprotic solvents. Structures such as 80 generally are not isolated but as in the case of 80 are carried on (when X = N3) to amino alcohols [83] or (when X = Br) to maleates [84] by reduction. Yields are good and for compounds unaffected by the harsher conditions needed to achieve the displacement reaction, use of the cyclic sulfite eliminates the added step of oxidation to the sulfate. 

Amines are at the same low oxidation level as alcohols and consequently are easily prepared by reduction. Amides and nitriles are reduced efficiently by LAH to amines. Nitriles give only primary amines while amides give 1°, 2°, or 3° amines depending on the number of carbon substituents on the amide nitrogen. The advantage of this method is that amides are easy to prepare from acid chlorides and amines while nitriles are available by displacement reactions. 

A range of methods has been developed for the protection of the carbonyl group in multifunctional aliphatic and alicyclic aldehydes and ketones. This has been necessary because in many multistage syntheses, modification of other functionalities (e.g. oxidation, reduction, hydrolysis, nucleophilic and electrophilic additions and displacements, etc.) requires a differing range of experimental conditions, and that protective group must be selected which is stable in the presence of the reaction medium. A further feature that should be noted is that... 

Example 7a is the idea behind the electrochemical series, a list of elements whose ions will displace the ions of another element from solution, as shown in Table 3. At comparable concentrations, ions of elements with larger negative reduction potentials (more easily oxidized) will displace those of elements with smaller negative reduction potentials from solution. In the short electrochemical series shown in Table 3, an element will displace the ions of any element lower in the list from aqueous solution. In some cases, however, the displacement reactions may be slow due to kinetic factors. 

Processes which involve oxidation (the loss of electrons or the gain of relative positive charge) and reduction (the gain of electrons or the loss of relative positive charge) are typical of these reactions. Use of Table 8.1, the activity series of common metals, enables chemists to predict which oxidation-reduction reactions are possible. A more active metal, one higher in the table, is able to displace a less active metal, one listed lower in the table, from its aqueous salt. Thus aluminum metal displaces copper metal from an aqueous... 

Despite the chemical diversity of the several hundred structures representing herbicidal activity, most reactions of herbicides fall within only a limited number of mechanistic types oxidation, reduction, nucleophilic displacements (such as hydrolysis), eliminations, and additions. "Herbicides", after all, are more-or-less ordinary chemicals, and their principal transformations in the environment are fundamentally no different from those in laboratory glassware. Figure 2 illustrates three typical examples which have received their share of classical laboratory study—the alkaline hydrolysis of a carboxylic ester (in this case, an ester of 2,4-dichlorophenoxyacetic acid, IX), the cycloaddition of an alcohol to an olefin (as in the acetylene, VI), and the 3-elimination of a dithiocarbamate which provides the usual synthetic route to an isothiocyanate (conversion of an N.N-dimethylcarbamic acid salt, XI, to methyl isothiocyanate). Allow the starting materials herbicidal action (which they have), give them names such as "2,4-D ester" or "pronamide" or "Vapam", and let soil form the walls of an outdoor reaction kettle the reactions and products remain the same. 

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