Reaction schemes, consecutive

The two basic complex reaction schemes, consecutive and parallel, were considered in an interesting and useful simple way by Millman and Katz [12], and illustrates... 

Optimisation results show that a batch addition of the reactant constitutes the best feed profile. According to the reaction scheme (consecutive-competitive) these profiles could be a priori determined (Burghardt and Skrzypek, 1974). The configuration of the... 

Figure 3-17. Consecutive application of two reaction schemes to model the oxidation of thioethers to sulfoxides.

Clearly, for symmetry reasons, the reverse process should also be considered. In fact, early versions of our reaction prediction and synthesis design system EROS [21] contained the reaction schemes of Figures 3-13, 3-15, and 3-16 and the reverse of the scheme shown in Figure 3-16. These four reaction schemes and their combined application include the majority of reactions observed in organic chemistry. Figure 3-17 shows a consecutive application of the reaction schemes of Figures 3-16 and 3-13 to model the oxidation of thioethers to sulfoxides. 

Reaction scheme, defined, 9 Reactions back, 26 branching, 189 chain, 181-182, 187-189 competition, 105. 106 concurrent, 58-64 consecutive, 70, 130 diffusion-controlled, 199-202 elementary, 2, 4, 5, 12, 55 exchange, kinetics of, 55-58, 176 induced, 102 opposing, 49-55 oscillating, 190-192 parallel, 58-64, 129 product-catalyzed, 36-37 reversible, 46-55 termination, 182 trapping, 2, 102, 126 Reactivity, 112 Reactivity pattern, 106 Reactivity-selectivity principle, 238 Relaxation kinetics, 52, 257 -260 Relaxation time, 257 Reorganization energy, 241 Reversible reactions, 46-55 concentration-jump technique for, 52-55... 

Fig. 21. Reaction scheme of crystal growth by chemical transport A, transport furnace having two consecutive heating coils.

The reactor system works nicely and two model systems were studied in detail catalytic hydrogenation of citral to citronellal and citronellol on Ni (application in perfumery industty) and ring opening of decalin on supported Ir and Pt catalysts (application in oil refining to get better diesel oil). Both systems represent very complex parallel-consecutive reaction schemes. Various temperatures, catalyst particle sizes and flow rates were thoroughly screened. 

More complicated reactions schemes, including first-order reversible consecutive processes and competitive consecutive reactions, are considered in a textbook by Irwin [89]. Professor Irwin s textbook also includes computer programs written in the BASIC language. These programs can be used to fit data to the models described. 

Density functional theory (B3LYP) has been used to investigate the mechanism of the cis-trans isomerization in Ir(H)2(CO)(C6H3 CH2P(H2) 2).300 The preferred mechanism involves two consecutive trigonal twists in which the complex passes through a distorted octahedral intermediate, as shown in reaction Scheme 19. 

Crosslinking of many polymers occurs through a complex combination of consecutive and parallel reactions. For those cases in which the chemistry is well understood it is possible to define the general reaction scheme and thus derive the appropriate differential equations describing the cure kinetics. Analytical solutions have been found for some of these systems of differential equations permitting accurate experimental determination of the individual rate constants. 

The distribution of products from the hydrogenation of vitrinite and inertinite separated from Australian Bayswater coal is shown in Fig. 3 and Fig. 4 respectively. Fig. 5 shows the distribution of products from the reduction of Soya-Koishi coal by CD + H20. The product distribution shows a similar tendency to that of Yubari coal shown in Fig. 2. Thus, it indicates that the Py-2, Py-1, A, 02 can be considered as intermediate products in a consecutive coal hydrogenation reaction scheme. 

We used 3 solvents to separate the hydrogenation and reduction products into fractions. If we can use a wider range of solvents with different solubility properties, the hydrogenation reaction scheme can be expressed as a consecutive reaction which has more steps. 

This landmark discovery paved the way for the development of transition metal-catalyzed hydroboration. The conversion of an alkene into an organoborane intermediate has made this a valuable synthetic technique, particularly since the development of enantioselective variants.9,10 They serve as synthons for numerous functional groups11 and are often subjected to a consecutive carbon-oxygen, carbon-carbon, boron-carbon, boron-chlorine, or carbon-nitrogen24 bond-forming reaction (Scheme 3). 

Looking back over the steps required to derive (5.290), it is immediately apparent that the same method can be applied to treat any reaction scheme for which only one reaction rate function is finite. The method has thus been extended by Baldyga (1994) to treat competitive-consecutive (see (5.181)) and parallel (see (5.211)) reactions in the limiting case where k -> oo.118 For both reaction systems, the conditional moments are formulated in terms of 72(X> and can be written as... 

The aldol reaction is probably one of the most important reactions in organic synthesis. In many industrially important hydroformylation processes selfcondensation of aldehydes is observed. Sometimes this consecutive reaction is favored as in the production of 2-ethyl hexanol. But synthetic applications of tandem hydroformylation/aldol reactions seem to be limited due regiose-lectivity problems of a mixed aldol reaction (Scheme 28). However, various tandem hydroformylation/intramolecular mixed aldol reactions have been described. 

In order to keep the spreadsheet reasonably small, the dimensions are much smaller than those in the Matlab examples. It is still a consecutive reaction scheme the spectra were recorded at 11 times and at 6 wavelengths. 

Wessjohann and coworkers described the design and synthesis of cyclic RGD pentapeptoids and related derivates by consecutive Ugi reactions (Scheme 23) [93]. 

In some reaction processes, both consecutive and parallel reactions may occur. In a reaction scheme such as... 

When reversible steps occur in a reaction scheme, distinctions between consecutive and parallel reactions cannot always be made. For example, the consecutive first-order reactions... 

The mechanisms considered above are all composed of steps in which chemical transformation occurs. In many important industrial reactions, chemical rate processes and physical rate processes occur simultaneously. The most important physical rate processes are concerned with heat and mass transfer. The effects of these processes are discussed in detail elsewhere within this book. However, the occurrence of a diffusion process in a reaction mechanism will be mentioned briefly because it can lead to kinetic complexities, particularly when a two-phase system is involved. Consider a reaction scheme in which a reactant A migrates through a non-reacting fluid to reach the interface between two phases. At the interface, where the concentration of A is Caj, species A is consumed in a first-order chemical rate process. In effect, consecutive rate processes are occurring. If a steady state is achieved, then... 

Consecutive condensations of 2-naphthol, allylamine, and dibromomethane comprised another route to naphthalene-condensed 1,3-oxazines. A preheated mixture of allylamine and dibromomethane was reacted with 2-naphthol 152 to yield the aminophenol intermediate 520, which was cyclized with the salt formed in the reaction of dibromomethane and diethylamine to give 3-allyl-3,4-dihydro-2//-naphth[l,2-< ][l,3]oxazine 521 on further reaction (Scheme 98) <2004SC2253>. 

The overall reaction scheme for the photolysis of TpT can thus be represented as in Chart 3. The general solutions for sets of consecutive... 

The reaction of phenol benzoylation catalyzed by a H-P zeolite (Si/Al ratio 75) has been studied, with the aim of determining the reaction scheme. The only primary product was phenylbenzoate, which then reacted consecutively to yield o- and p-hydroxybenzophenone and benzoylphenylbenzoate isomers, via both intermolecular and intramolecular mechanisms. 

Industrially relevant consecutive-competitive reaction schemes on metal catalysts were considered hydrogenation of citral, xylose and lactose. The first case study is relevant for perfumery industry, while the latter ones are used for the production of sweeteners. The catalysts deactivate during the process. The yields of the desired products are steered by mass transfer conditions and the concentration fronts move inside the particles due to catalyst deactivation. The reaction-deactivation-diffusion model was solved and the model was used to predict the behaviours of semi-batch reactors. Depending on the hydrogen concentration level on the catalyst surface, the product distribution can be steered towards isomerization or hydrogenation products. The tool developed in this work can be used for simulation and optimization of stirred tanks in laboratory and industrial scale. 

Many organic hydrogenation and isomerization reactions have a parallel-consecutive reaction scheme of the type... 

Froment and Bischoff (1990) have developed another approach to include the effect of coking, considering the composition of the feed, catalyst temperature, and activity. They assumed that coke formation follows a reaction parallel or consecutive to the main reaction scheme ... 

The dehydration of alcohols on solid catalysts is one of the first catalytic reactions discovered and has been studied intensively for many decades. During years of experimental work, a general parallel—consecutive reaction scheme (Scheme 2 below) has been developed by gradual addition of... 

The kinetics of the ammoxidation of xylenes over a vanadium catalyst and mixed vanadium catalysts were studied. The reaction rate data obtained were correlated with the parallel consecutive reaction scheme by the rate equations based upon the Langmuir-Hinshelwood mechanism where the adsorption of xylenes was strong. The reaction rates of each path are remarkably affected by the kind of xylene and catalyst. The results of the physical measurement of catalysts indicated that the activity and the selectivity of reaction were affected by the nature and the distribution of metal ions and oxygen ion on catalyst surface. 

As an example for reactions in series or consecutive reactions, the simple reaction scheme... 

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