Overall reaction equation

Now although the chemical desorption step is independent of rj, the surface coverage will increase as rj becomes more negative and this will affect tic.D - Since two electrons will be required for the overall reaction, equation 20.98 can be expressed in terms of i... 

A typical featnre of reactions involving the minority carriers are the limiting currents developing when the snrface concentration of these carriers has dropped to zero and they mnst be snpplied by slow dilfnsion from the bulk of the semiconductor. A reaction of this type, which has been stndied in detail, is the anodic dissolution of germanium. Holes are involved in the first step of this reaction Ge — Ge(II), and electrons in the second Ge(ll) —> Ge(IV). The overall reaction equation can be written as... 

This overall reaction equation points to the fact that copper phthalocyanine formation formally requires two reduction equivalents. 

A detailed mechanism was proposed for 69a as an example. The overall reaction (equation 40) finally produced the disilyl compound 74a with a yield not much higher than 50%. However, unexpected resnlts were obtained nsing nltrasonic irradiation during the electrolysis. The apparent cnrrent efficiency increased np to 200% giving, for example, 71% of disilane 74b (and by-prodncts) bnt no monosilane 71b or 72b after passage of 2.5 Faradays per mole of 69b. 

There are quite a few situations in which rates of transformation reactions of organic compounds are accelerated by reactive species that do not appear in the overall reaction equation. Such species, generally referred to as catalysts, are continuously regenerated that is, they are not consumed during the reaction. Examples of catalysts that we will discuss in the following chapters include reactive surface sites (Chapter 13), electron transfer mediators (Chapter 14), and, particularly enzymes, in the case of microbial transformations (Chapter 17). Consequently, in these cases the reaction cannot be characterized by a simple reaction order, that is, by a simple power law as used for the reactions discussed so far. Often in such situations, reaction kinetics are found to exhibit a gradual transition from first-order behavior at low compound concentration (the compound sees a constant steady-state concentration of the catalyst) to zero-order (i.e., constant term) behavior at high compound concentration (all reactive species are saturated ) ... 

Before the general acceptance of the chemiosmotic model for oxidative phosphorylation, the assumption was that the overall reaction equation would take the following form ... 

All of these hydrolysis reactions are energetically favorable (AC0 < 0), but they do not occur directly because ATP reacts slowly with water. However, hydrolysis of ATP is the indirect result of other reactions in which it participates. For example, as we showed in Section 15-4D, equilibrium for the direct formation of an ester from a carboxylic acid and an alcohol in the liquid phase is not very favorable (Equation 15-2). However, if esterification can be coupled with ATP hydrolysis (Equation 15-3), the overall reaction (Equation 15-4) becomes much more favorable thermodynamically than is direct esterification. 

Overall reaction equations are linear combinations of chemical equations of stages, i.e., they are obtained by the addition of chemical equations of stages multiplied by certain numbers (positive, negative, or zero). The numbers must be chosen in such a way that the overall equations contain no intermediates. According to Horiuti, such numbers are called stoichiometric. To illustrate this notion by a simple example, let us assume that the mechanism of oxidation of S02 on the surface of a solid catalyst, e.g., platinum, is described by the following scheme ... 

A set of stoichiometric numbers of the stages producing an overall reaction equation is called, after Horiuti, a reaction route. Thus, in scheme (35) there are two reaction routes, N(l) and iV(2) route Na> cannot be obtained from N(i) through multiplication by a number. Therefore, routes N(1) and N(2) are essentially different, although their respective overall equations are identical. 

If stoichiometric numbers of all the slow stages are the same, then v equals these numbers and, consequently, is constant. In these cases it is always possible to write the overall reaction equation in such a way that v = 1. If this is done,... 

Despite the expenditure of a tremendous amount of effort throughout the world, the two original methods employed in the manufacture of copper phthalocyanine are still used. In the first, a mixture of phthalic anhydride, urea and copper(I) chloride is heated in a high-boiling solvent such as nitrobenzene or trichlorobenzene in the presence of a catalytic amount of ammonium molybdate. The crude copper phthalocyanine is filtered off and the solvent recovered by distillation. The urea acts as a source of nitrogen and the first step in the overall reaction (equation 18) is conversion of phthalic anhydride to phthalimide (219) by ammonia liberated by the urea. More ammonia then converts the phthalimide to l-keto-3-iminoisoindoline (220) and finally to l-amino-3-iminoisoin-dolenine (221). All three intermediates have been isolated and identified. In the presence of copper chloride the l-amino-3-iminoisoindolenine undergoes conversion to the copper complex of phthalocyanine. 

So the overall reaction (Equation 8.17) occurs at a redox potential close to that of the Nin/Ni° system, i.e. at -1.1 V/SCE, whereas Zn11 ions are reduced at ca. -1.4 V/SCE in DMF, and aryl halides are reduced at between -2 and -2.7 V/SCE. In addition, apart from N02, sensitive functional groups can be present on the ring, o-arylnickel compounds are reducibly converted into Ar-Ar (para- or meta-substituted compounds) or into Ar-H (ortho-substituted compounds). 

What is the site of an anodic attack, and is this a function of the distribution of the electron density in the molecule In Et-0-CH2-CH2-CN (note the overall reaction equation),... 

For CO2 we consider only the reversible reaction with primary and secondary alkanolamines as shown in the overall reaction equation [7] ... 

The formal overall reaction equations are straightforward, but they hide a tremendous amount of mechanistic detail as we discuss later on in this chapter ... 

These are (a) 0 elimination, (b) a elimination and (c) hydrolysis. In 0 elimination, the proposed reactions are shown in Equation 7. Therefore, the stoichiometry of the reaction is two moles of dehydroalanine, one mole of elemental sulfur and one mole of disulfide as shown by the overall reaction (Equation 8). 

The P450 shunt pathway and peroxygenase activity of peroxidases share identical overall reaction equations. P450s generally have high Km values for H 202 values of 15 mM... 

The oxides of the transition metals can be reduced by carbon according to the following overall reaction (equation 5). 

Synthesis ofNOz(g) from the elements [reaction (c) in Fig. 9.12]. The overall reaction equation has 4 mol of N02. Thus the required reaction is 4 times the formation reaction for N02 ... 

The overall reaction [Equation (7-4)], for which the rate expression is nonele-mentary, consists of the sequence of elementary reactions, Equations (7-5), (7-7), and 7-9. ... 

On the basis of the experimental data summarized above, and taking into account the chemistry of the elements involved in strongly acidic and alkaline media [15], the following overall reaction equations can be proposed for the anodic dissolution of the III-V semiconductors under consideration ... 

The form of the flow calorimetric equations described earlier can also be manipulated to incorporate Michaelis-Menten parameters such as the Michaelis constant, as well as yielding the first order rate constant and enthalpy for the overall reaction, Equation (6). 

The reversible reaction of carbon dioxide with water and OH ions has the overall reaction equation (Table 9.2a)... 

Write down the overall reaction equation for the, addition of a bromine molecule to ethene. 

Miyamoto et al. [90] proposed a dual-site Eley-Rideal mechanism which is a better description of the mechanism. In this mechanism ammonia is strongly adsorbed as NH4. NO from the gas phase reacts with the adsorbed ammonia species to form N2, H2O, and V-OH. The latter is oxidized by oxygen from the gas phase or lattice oxygen to V =0. The overall reaction equations are... 

A is correct. If we look at Reactions 1 and 2 as two steps of a single reaction, we know that the rate of the slow step is equal to the rate of the overall reaction. Equation 1 measures the time necessary for a specific number of moles of I3 to be used by Reaction 2. (Notice that the rate of change of V2[S2032-] will be equal to the rate of change of [I3-]) If Reaction 2 were not the fast step, then Equation 1 would not measure the rate of Reaction 1 accurately. Since Reaction 2 is the fast step, the time t required to use up 72[S2032-] is equal to the time needed to produce [I3 ]. The [I3 ] concentration produced divided by the time necessary to produce it is the rate of Reaction 1. Equation 1 is not derivable from the rate laws of Reactions 1 and 2. 

During flame combustion, temperatures in excess of 1700K occur. At those temperatures, the reaction between the air constituents nitrogen and oxygen is thermodynamically favored, resulting in the formation of nitrogen oxides, according to the overall reaction equation... 

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