Reaction mechanisms reduction reactions

To date, synthetically useful enantioselective hydroalumination is limited to the asymmetric reductive ring-opening reaction of bicycHc ethers. In spite of the fact that further studies are necessary to get a detailed understanding of the reaction mechanism, this reaction provides a new route to various cycloalkenol derivatives, which are useful intermediates in the preparation of biologically active compounds. 

Computers and Chemical Engineering, 30, 889 (2006). Reaction Mechanism Reduction and Optimization for Modeling Aviation Fuel Oxidation using Standard and Hybrid Genetic Algorithms. 

As will become evident in this section, in the net transformation from reactant —s-product transformations many of the synthetically useful reactions involving >C=C<"+ are analogous to those involving neutral, un-ionized carbon-carbon double bonds (e.g. the Diels-Alder reaction, oxidation/reduction reactions, nucleophilic addition etc.). However, many of the reactions involving a neutral >C=C< often require the presence of an activating substituent in order to make the alkene more electron-deficient. In a sense, one-electron oxidation of an alkene to its radical cation provides a simple and unique mechanism for increasing the electrophilic (and, of course, radical) properties of... 

Dr. Fred Guengerich at Vanderbilt University has published mechanistic schemata for cytochrome P450 involvement in an extensive array of both common and uncommon oxidative reactions and reductive reactions. Some of those are exhibited later in this chapter in a brief consideration of reductive reactions. Mechanisms for carbon hydroxylation, heteroatom oxygenation, N-dealkylation, O-dealkylation, alcohol oxidation, arene epoxidation, phenol formation, oxidation of olefins and acetylenes, reduction of nitro compounds, reductive dehalogenation, and azo reduction, to name a few, are provided. 

Kertesz, V., Van Berkel, G.J. (2005) Monitoring Ionic Adducts to Elucidate Reaction Mechanisms Reduction of Tetracyanoquinodimethane and Oxidation of Tripheny-lamine Investigated Using On-line Electrochemistry/Electrospray Mass Spectrometry. J. Solid State Electrochem. 9 390-397. 

Elliott, L., Ingham, D.B., Kyne, A.G., Mera, N.S., Pourkashanian, M., Wilson, C.W. Reaction mechanism reduction and optimization using genetic algorithms. Ind. Eng. Chem. Res. 44,... 

The key step of the reaction mechanism is reaction of the titanium complex 118 with the a,co-enone to give the titanaoxacyclopentane 140, which reacted with diphenylsilane by the cleavage of the Ti-0 bond to afford the alkyltitanium compound 141. Reductive elimination furnished the siloxane 138 and the catalyst entered the cycle again (Scheme 62). 

For tliis model tire parameter set p consists of tire rate constants and tire constant pool chemical concentrations l A, 1 (Most chemical rate laws are constmcted phenomenologically and often have cubic or otlier nonlinearities and irreversible steps. Such rate laws are reductions of tire full underlying reaction mechanism.)... 

For heavy drain discharges of alkaline cells, there is no useful capacity after this point because the rate of discharge of the ZnMn204 is quite slow. But for lighter drain discharges, further reduction of the cathode is possible. The reaction mechanisms are not entirely clear, but there is some evidence for the formation of a final reaction product resembling hausmannite [1309-55-3] Mn O. ... 

Sodium hydrosulfite or sodium dithionate, Na2S204, under alkaline conditions are powerful reducing agents the oxidation potential is +1.12 V. The reduction of -phenylazobenzenesulfonic acid with sodium hydrosulfite in alkaline solutions is first order with respect to -phenylazobenzenesulfonate ion concentration and one-half order with respect to dithionate ion concentration (135). The SO 2 radical ion is a reaction intermediate for the reduction mechanisms. The reaction equation for this reduction is... 

An alternative reaction mechanism has been suggested for nitroarylation of enolates. An impetus for considering other mechanisms is the fact that the by-products which might be expected from aryl radicals, such as reduction products from hydrogen abstraction from the solvent or biaryls from coupling, are not observed. One alternative is that, rather than being a chain process, the reaction may involve recombination whereby the radicals combine more rapidly than they separate. 

FIGURE 25.32 A reaction mechanism for HMGCoA reductase. Two successive NADPH-dependent reductions convert the thioester, HMGCoA, to a primary alcohol. 

The first systematic theoretical study on dihydro-1,2,4-triazines was recently carried out (98JOC5824) the stabilities of all the possible unsubstituted dihydro-1,2,4-triazines were calculated using various theoretical methods, all reliable calculation methods consistently show that the 2,5-dihydro isomer 98 is the most stable. This is in perfect agreement with the experimental observations all the synthetic methods used for the preparation of dihydro-1,2,4-triazines result in 2,5-dihydro isomer 98, provided the structures of the reactants and the reaction mechanism allow its formation. Thus, although Metze and Scherowsky (59CB2481) claimed the formation of 1,2-dihydro-1,2,4-triazine 92 (R = = Ph) in the reduction... 

Mn(acac)3 in the above mechanism undergoes an intramolecular photooxidation-reduction reaction arising from the ligand to metal charge transfer process (LMCT). 

The mechanism of the oxygen reduction reaction is by no means as fully understood as the h.e.r., and a major experimental difficulty is that in acid solutions (pH = 0) E02/H20 = 1 23, which means that oxygen will start to be reduced at potentials at which most metals anodically dissolve. For this reason accurate data on kinetics is available only for the platinum metals. In the case of an iridium electrode at which oxygen reduction is relatively rapid, a number of reaction sequences have been proposed, of which the most acceptable appear to be the following ... 

In addition to the basic corrosion mechanism of attack by acetic acid, it is well established that differential oxygen concentration cells are set up along metals embedded in wood. The gap between a nail and the wood into which it is embedded resembles the ideal crevice or deep, narrow pit. It is expected, therefore, that the cathodic reaction (oxygen reduction) should take place on the exposed head and that metal dissolution should occur on the shank in the wood. 

The Mecrwein-Ponndoi f-Verlev reaction involves reduction of a ketone by treatment with an excess of aluminum triisopropoxide. The mechanism of the process is closely related to the Cannizzaro reaction in that a hydride ion acts as a leaving group. Propose a mechanism. 

We said in Section 17.4 that carboxylic acids are reduced by L1AIH4 to give primary alcohols, but we deferred a discussion of the reaction mechanism at that time. In fact, the reduction is a nucleophilic acyl substitution reaction in which —H replaces -OH to give an aldehyde, which is further reduced to a primary alcohol by nucleophilic addition. The aldehyde intermediate is much more reactive than the starting acid, so it reacts immediately and is not isolated. 

Another possibility is that one of the reactants is particularly mobile, this is apparent in certain solid—gas reactions, such as the reduction of NiO with hydrogen, which is a well-characterized nucleation and growth process [30,1166]. Attempts have been made to use the kinetic equations developed for interface reactions to elucidate the mechanisms of reactions between the crystalline components of rocks under conditions of natural metamorphism [1167,1168]. 

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