Scheme of reactions

Reactions of solids. Scheme of reaction pathways indicating relationships with kinetic characteristics... 

Figure 1.7 Reaction scheme of reaction of Cajs with Hads to produce CH4 on Ru(OOOl) surface. Coverages of 25% and 11% are compared. Energies with respect to gas phase [4].

Figure 5.3-7. Scheme of reaction between diazotized sulphanilic acid (B) and 1-naphthol (A). 

Radiolysis of CO, both in the liquid and gaseous states, also leads to C02 and C302 formation, the latter product appearing mainly as a polymeric solid23-27. A scheme of reactions consisting of the initial production of a carbon and an oxygen atom, followed by (10)-(12) and... 

In Fig. 5.5a a simple scheme of reaction steps is proposed. Some of the assumptions of our model are summarized in Table 5.1. The short-hand representation of a surface site is a simplification that does not take into account either detailed structural aspects of the oxide surface or the oxidation state of the metal ion and its coordination number. It implies (model assumption 2 in Table 5.1) that all functional surface groups, such as those in a cross-linked polyhydroxo-oxo acid, are treated as if they were identical. 

The kinetic scheme of reaction (40), followed by reaction (42), was used to investigate the influence of added chloride ion on the epr spectral intensity of Cl-PBN. This variable decreased by a factor of about 50 in going from... 

If one would be able to derive from the experimental data an accurate rate equation like (12) the number of terms in the denominator gives us the number of reactions involved in forward and backward direction that should be included in the scheme of reactions, including the reagents involved. The use of analytical expressions is limited to schemes of only two reaction steps. In a catalytic sequence usually more than two reactions occur. We can represent the kinetics by an analytical expression only, if a series of fast pre-equilibria occurs (as in the hydroformylation reaction, Chapter 9, or as in the Wacker reaction, Chapter 15) or else if the rate determining step occurs after the resting state of the catalyst, either immediately, or as the second one as shown in Figure 3.1. In the examples above we have seen that often the rate equation takes a simpler form and does not even show all substrates participating in the reaction. 

FIGURE 8.1 General scheme of reactions involved in the sol-gel processing. 

The data clearly indicate that the only primary product was phenylbenzoate, while all the other compounds formed by consecutive reactions upon the ester. Therefore, the scheme of reaction is that one summarized in Figure 3. The formation of the ester as the only primary product represents one important difference with respect to the Friedel-Crafts benzoylation of phenol with benzoylchloride or benzyltrichloride, catalyzed by AICI3. In the latter case, in fact, the product of para-C-acylation (p-hydroxybenzophenone) is the main product of reaction this is due to the fact that AICI3 coordinates with the 0 atom of the hydroxy group in phenol, and makes it less available for the ester formation, due to both electronic and steric reasons. 

The scheme of reactions proposed to explain the products obtained is shown, after small modifications, in Scheme 8. Primary radicals 12 formed at the anodes produce with added 30 or 36 (equation lOe) the substituted benzyl or allyl radicals 38, which can dimerize to 39 or can couple with the added olefin to form radicals 40 or 41. For allyl radical (38) a 1,1 - or l,3 -coupling is possible yielding 41 and 40, respectively. Further couplings of 40 and 41 with the primary radical 12 produce 39 and head-to-tail dimer 42, respectively. It was evident from the products obtained that the coupling of 38 in the 1-position occurs 5 to 11 times faster than in the 3-position. However, for readily polymerizable olefins, rather polymerization occurs, in particular at graphite electrodes. At Pt electrodes both dimers 39 and 42 are formed, but for Cu electrodes exclusively dimers 39 were obtained with moderate yields. Thus, an indirect electrolysis including the oxidation of copper to Cu+ ions and their further reaction with 5 yielding intermediate RCu was considered, but not proved . ... 

Intercalation of both cationic and neutral (solvated) molecular species in MXj is particularly important when the reaction occurs in the presence of polar solvents, especially at low temperatures (Fig. 8.8). A simplified scheme of reactions which explains this type of intercalation has been proposed by Schollhorn (1980) ... 

It is further observed that an increase in reaction efficiency corresponds to decrease in fluorescence efficiency. The last column gives the sum of the two processes which may be taken as the contribution by the singlet excited state. The values vary within small limits. The remainder of the excited molecules must either degrade to the triplet state by inter-system crossing or to the ground state by internal conversion. The scheme of reaction is suggested as follows ... 

In earlier work, acetylene was not considered as an intermediate in the combustion proper, but, rather, as a product of thermal decomposition occurring as a side reaction due to the heat released by oxidation of part of the hydrocarbon. Egloff, Schoad, and Lowry (21) suggested, for example, the following scheme of reactions for ethane ... 

The scheme of reactions (5)-(8) is similar in certain aspects to that of electron transfer processes occurring in the membranes of photosynthesiz-ing organisms, where the light absorption also induces a trans-membrane potential difference. The above scheme of processes in multilayer systems explaining the appearance of the photoelectromotive force requires further refinement. But even the data available at present allow these systems to be regarded firstly as convenient models for analyzing the processes occurring... 

The regularities observed are accounted for by the following scheme of reaction mechanism ... 

Fig. 9. The suggested scheme of reaction, states of P-450. W is a weak donor...

They suggested the following tentative scheme of reactions ... 

No Process Scheme of reaction mechanism Rate equations... 

Geometrical representations of sequences are very helpful in the study of the kinetics of certain scheme of reactions and will be used in the following presentation. 

To explain their results on the conversion of sucrose to glucose and fructose by the enzyme invertase, Michaelis and Menten proposed in 1913 the following scheme of reactions ... 

The solution kinetics involves three fundamental types of experiment, namely (i) rate law, (ii) stereochemistry and (iii) variation of rate constant with structure or environment. Each one permits the analysis of slightly different aspects of a reaction, and then develops a scheme of reaction classification which throws light on the behaviour of a reaction in each experimental situation. It is useful to briefly discuss the role of each of the three types of experimental investigation in the study of complex substitution reactions. 

The spur processes described for the liquid state should apply to solids. As compared to the scheme of reactions (I)—(IX), solvation is to be excluded. Localization in the sense that the particle would preserve some non negligible mobility as such, is also to be discarded in most cases. 

Fig. 14.2 Scheme of reactions occurring in the human body under oxidative stress [4]... 

The asphaltenes appear to be the final (excluding carbenes and carboids, those organic fractions of petroleum that are insoluble in toluene or benzene) condensation product as indicated from oxidation where the scheme of reaction (66, 67) is ... 

From the scheme of reactions given in Fig. 99 it follows that in calculating the thermodynamic constants (Tables XII and XIII) of any intermediate or final compound, the recommended constants of the initial compounds and the standard (tabulated) constants of reference substances were used. For instance, in the case of fayalite—Fe2Si04 — the accepted constants of the... 

In the polymerization scheme of reaction (9-59), insertion of a monomer results in an interchange of the polymer substituent and the lattice vacancy. These are not equivalent positions in the crystal lattice of the catalyst. Under normal polymerization conditions the macromolecular alkyl appears to shift back to its original position before the next monomer is added. Isotactic polymers are produced from olefins and catalysts of this type because the monomer always inserts by cis addition with the unsubstituted carbon of the olefin attached to the transition metal which always has the same chirality. If the polymer chain and vacant orbital were to exchange initial positions, however, then the placements of successive monomers would alternate stereochemically, providing syndiotacticity. 

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