Oxidation stoichiometric reactions

This process had been studied by Monsanto [19] and Gulf [20, 21]. Its advantage should be to use toluene instead of benzene. In a first step, toluene is converted into stilbene by oxidative coupling (dehydrodimerization) at 600°C over lead oxide supported on alumina. The oxygen used in the reaction comes from the lead oxide (stoichiometric reaction). 

A rational classification of reactions based on mechanistic considerations is essential for the better understanding of such a broad research field as that of the organic chemistry of Pd. Therefore, as was done in my previous book, the organic reactions of Pd are classified into stoichiometric and catalytic reactions. It is essential to form a Pd—C cr-bond for a synthetic reaction. The Pd— C (T-bond is formed in two ways depending on the substrates. ir-Bond formation from "unoxidized forms [1] of alkenes and arenes (simple alkenes and arenes) leads to stoichiometric reactions, and that from oxidized forms of alkenes and arenes (typically halides) leads to catalytic reactions. We first consider how these two reactions differ. 

Typical nucleophiles known to react with coordinated alkenes are water, alcohols, carboxylic acids, ammonia, amines, enamines, and active methylene compounds 11.12]. The intramolecular version is particularly useful for syntheses of various heterocyclic compounds[l 3,14]. CO and aromatics also react with alkenes. The oxidation reactions of alkenes can be classified further based on these attacking species. Under certain conditions, especially in the presence of bases, the rr-alkene complex 4 is converted into the 7r-allylic complex 5. Various stoichiometric reactions of alkenes via 7r-allylic complex 5 are treated in Section 4. 

TT-Aliylpalladium chloride reacts with a soft carbon nucleophile such as mal-onate and acetoacetate in DMSO as a coordinating solvent, and facile carbon-carbon bond formation takes place[l2,265], This reaction constitutes the basis of both stoichiometric and catalytic 7r-allylpalladium chemistry. Depending on the way in which 7r-allylpalladium complexes are prepared, the reaction becomes stoichiometric or catalytic. Preparation of the 7r-allylpalladium complexes 298 by the oxidative addition of Pd(0) to various allylic compounds (esters, carbonates etc.), and their reactions with nucleophiles, are catalytic, because Pd(0) is regenerated after the reaction with the nucleophile, and reacts again with allylic compounds. These catalytic reactions are treated in Chapter 4, Section 2. On the other hand, the preparation of the 7r-allyl complexes 299 from alkenes requires Pd(II) salts. The subsequent reaction with the nucleophile forms Pd(0). The whole process consumes Pd(ll), and ends as a stoichiometric process, because the in situ reoxidation of Pd(0) is hardly attainable. These stoichiometric reactions are treated in this section. 

Magnesium hydroxide can also be produced by slaking or pressure hydrating various reactive grades of magnesium oxide. The reaction is highly exothermic (AH gg = —40.86 kJ/mol (—9.77 kcal/mol)) to produce crystalline form at stoichiometric water addition ... 

According to Figure 3, hydroperoxides are reduced to alcohols, and the sulfide group is oxidized to protonic and Lewis acids by a series of stoichiometric reactions. The sulfinic acid (21), sulfonic acid (23), sulfur trioxide, and sulfuric acid are capable of catalyzing the decomposition of hydroperoxides to nonradical species. 

The destruction and removal of trichloroethylene (TCE) by reaction with OXITOX , (sodium carbonate activated by Mg and Mn oxides and carbonates), proceeds through the following stoichiometric reaction ... 

Therefore at constant temperature of 300°C and 7.5 psig of pressure, the system uses air that has 500 PPM TCE in it. Complete oxidation of 500 PPM TCE would consume only 750 PPM of oxygen as can be seen from the stoichiometric reaction. This is not a significant change from the oxygen content of air. 

The chemical reactions that occnr in flames transform an initial reactant mixtnre into final reaction prodncts. In the case of fnel-oxygen combns-tion, the final prodncts are principally water vapor and carbon dioxide, althongh nnmerons other prodncts snch as carbon monoxide may be formed, depending on the reactant composition and other factors. If the ratio of fnel-to-oxygen is stoichiometric, the final reaction prodncts, by definition, contain no excess fnel or oxygen. Theoretically, this means that partial oxidation prodncts snch as CO (itself a fnel) are not formed. In reality, partial oxidation prodncts snch as CO or OH are formed by high tem-peratnre reactions. For example, the molar stoichiometric reaction of methane is written ... 

Hegedus et al. have thoroughly studied the homogeneous hydroamination of olefins in the presence of transition metal complexes. However, most of these reactions are either promoted or assisted, i.e. are stoichiometric reactions of an amine with a coordinated alkene [98-101] or, if catalytic, give rise to the oxidative hydroamination products, as for example in the cyclization of o-allylanilines to 2-alkylindoles [102, 103], i.e. are relevant to Wacker-type chemistry [104]. 

Due to participation in oxidation-reduction reactions the reducing or inflammable gases affect the stoichiometricity of oxide and, consequently the concentration of stoichiometric defects which usually control the dope electric conductivity of adsorbent [26, 67, 85, 86, 90]... 

Oxidations Using Oxoammonium Ions. Another oxidation procedure uses an oxoammonium ion, usually derived from the stable nitroxide tetramethylpiperidine nitroxide, TEMPO, as the active reagent.31 It is regenerated in a catalytic cycle using hypochlorite ion32 or NCS33 as the stoichiometric oxidant. These reactions involve an intermediate adduct of the alcohol and the oxoammonium ion. 

These reactions to form aryl tin bonds could occur by initial oxidative addition of the aryl halide or the distannane. The stoichiometric reaction between [(PPh3)2Pd(Ph)(I)] and Me3SnSnMe3 in the presence of chloride generated good yields of the aryltin product. This result suggests that the reactions occur by initial oxidative addition of aryl halide. 

One of the conclusions deduced from the thermochemical cycle 2 in Table V, for instance, is that in the course of the catalytic combustion of carbon monoxide at 30°C, the most reactive surface sites of gallium-doped nickel oxide are inhibited by the reaction product, carbon dioxide. This conclusion ought to be verified directly by the calorimetric study of the reaction. Small doses of the stoichiometric reaction mixture (CO + IO2) were therefore introduced successively in the calorimetric cell of a Calvet microcalorimeter containing a freshly prepared sample of gallium-doped... 

Aryl phosphites are widely used as inhibitors of oxidation. Phosphites react with hydroperoxides and are oxidized into phosphates by the following stoichiometric reaction [1-10] ... 

In a stoichiometric reaction the 6jr-allyl)palladium complex 66 was isolated and characterized5815. In a subsequent reaction the jr-allyl complex was reacted with benzoquinone in acetic acid to give an allylic acetate, which was hydrolyzed and oxidized to theaspirone. Interestingly, a quite high diastereoselectivity for the turns methyl isomer was obtained in the palladium-mediated spirocyclization (equation 28). 

Consider the complete stoichiometric reaction for the oxidation of butane ... 

Figure 1.1 Schematic representation of a well known catalytic reaction, the oxidation of carbon monoxide on noble metal catalysts CO + Vi 02 —> C02. The catalytic cycle begins with the associative adsorption of CO and the dissociative adsorption of 02 on the surface. As adsorption is always exothermic, the potential energy decreases. Next CO and O combine to form an adsorbed C02 molecule, which represents the rate-determining step in the catalytic sequence. The adsorbed C02 molecule desorbs almost instantaneously, thereby liberating adsorption sites that are available for the following reaction cycle. This regeneration of sites distinguishes catalytic from stoichiometric reactions.

The search for low-molecular weight (phenoxyl)copper(II) complexes as functional models for GO, which would mimick this reactivity, had a promising start in 1996 when Tolman and co-workers (202) reported that electrochemical one-electron oxidation of Cull(,L,lil 2)(bcnzylalcoholatc) (Fig. 27) resulted in the formation of benzaldehyde (46%) and some other decomposition products of the ligand H L,Bu2 in <5% yield and probably a Cu(I) species of unknown composition. These authors suggest that a (phenoxyl)copper(II) intermediate Cull(,L,l l 2 )(bcn-zylalcoholate)]+ is formed and that the reaction sequence, as in Fig. 8, leads to the observed products. Although this represents a stoichiometric reaction, it demonstrated for the first time that GO chemistry can be successfully modeled. 

The importance of these radicals in catalytic processes may be evaluated by studying their behavior in stoichiometric reactions and by extrapolating this information to catalytic conditions. In following the stoichiometric reactions, magnesium oxide has been an excellent model surface since the three types of oxygen ions may be selectively formed and are stable at temperatures where most hydrocarbons of interest will react. Magnesium oxide, on the other hand, is basic and reactive itself therefore intermediates may react differently on this surface than on silica, for example. 

Oxidative Dehydrogenation of Ethane. The dehydrogenation of alkanes also occurs, but in a catalytic manner, over molybdenum supported on silica (22,23). In addition to the stoichiometric reactions, the role of the 0 ion in this catalytic reaction is further suggested by the observation that N2O is an effective oxidant at temperatures as low as 280°C, but no reaction is observed at these temperatures with O2 as the oxidant (22). It should be noted that at moderate temperatues N2O gives rise to 0 , whereas O2 yields O2 over Mo/Si02. Under steady-state conditions the rates of formation of C2Hi were in the ratio of 7 1 at 375°C and 3.7 1 at 450°C when N2O and O2 were used as the oxidants, respectively (23). ... 

As an alternative to the oxidation of sulphides and sulphoxides (see Chapter 10), sulphones can be prepared by the nucleophilic substitution reaction of the sulphinite anion on haloalkanes. In the absence of a phase-transfer catalyst, the reaction times are generally long and the yields are low, and undesirable O-alkylation of the sulphinite anion competes with S-alkylation. The stoichiometric reaction of the preformed tetra-n-butylammonium salt of 4-toluenesulphinic acid with haloalkanes produces 4-tolyl sulphones in high yield [1], but it has been demonstrated that equally good... 

The stoichiometric reaction of sulphides with ammonium tribromides under basic conditions leads to sulphoxides [10]. In a modified procedure, oxidation in I80-enriched water produces the 180-labelled sulphoxide [11]. 

The stoichiometric process can be made catalytic when the latter is reoxidised to the high-valent species. The schematic process is portrayed in Figure 14.13. In older literature, the commonest oxidant used in stoichiometric reactions is potassium permanganate (KMn04), but in the last decades the focus... 

Although cyclizations from the direct anodic oxidation of acyclic 1,3-dicarbonyl compounds have not been reported, the analogous mediated reactions have been studied [24]. Snider and McCarthy compared oxidative cyclization reactions using a stoichiometric amount of Mn(OAc)3 with oxidations using a catalytic amount of Mn(OAc)3 that was recycled at an anode surface (Scheme 11). In the best case, the anodic oxidation procedure led to a 59% yield of the desired bridged bicyclic product with the use of only 0.2 equivalents (10% of the theoretical amount needed) of Mn(OAc)3- Evidence that the reaction was initiated by the presence of the mediator was obtained by examining the electrolysis reaction without the added Mn(OAc)3. In this case, none of the cyclized product was obtained. For comparison, the oxidation using... 

These iodometric calibration methods are based on the assumption that there is a stoichiometric reaction between ozone and the iodine in the various potassium iodide procedures. Three essentially independent methods have been used to test the accuracy of this assumption measuring the absorption of ultraviolet radiation at 254 nm by ozone in air, measuring the absorption of infrared radiation at 9,480 nm by ozone in air, and determining the ozone concentration in air by titration with nitric oxide. 

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