INFLUENCE OF THE REACTION CONDITIONS

The reaction conditions involve variables like temperature, pressure, solvent, the nature of associated metals or of counterions in the case of polar reactions, and the presence of additives such as salts, Lewis acids or bases. All these variables can modify the substrate-reagent interactions. 

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In DMS0/tert.Bu0K/02 quantum yields found were 3 x I0 4 for 50 and 5 X 104 for 49. These values are not regarded as maximum values, as a strong influence of the reaction conditions was noted 104). Whereas, in luminol-type compounds, any substitution in the cyclic hydrazide ring system renders the compound non-chemiluminescent 105>, this is not the case with these open-chain hydrazides the methylated compounds 49, 50 (R=N(CH3)NH2) and 50 (R=N(CH3)NH(CH3)) were also found to be chemiluminescent, though less so than the unsubstituted hydrazide. E. H. White and coworkers 104> therefore suggest a mechanism via acyl anions for the non-cyclic hydrazides (see Section VI. C.). 

It is important to emphasize here that the model in such a form allows one to simulate the influence of the reaction conditions. The temperature dependence of all the relative probabilities appears in the exponential expressions for the rate constants and the equilibrium constants. The olefin pressure influences the isomerization-insertion relative probabilities. As a result, both, temperature and olefin pressure influence the values of the absolute probabilities for all the reactive events considered. In the following use has been made of calculated reaction rates [13f] to evaluate all stochastic probabilities, unless otherwise stated. 

With regard to the influences of the reaction conditions, the following experimental results were obtained. 

Table V. Influence of the Reaction Conditions on the Optical Yield in the Hydroformylation of Different Olefins with HRh(CO) (P< 3)3 and ( —)-DIOP pn2 = pco...

The greater versatility of rhodium catalysts 21) and the promising results obtained in the first experiments in asymmetric hydroformylation 5,22 24) encouraged research in this field. A great number of substrates have been hydroformylated and a relatively large number of chiral ligands have been used. Furthermore, the influence of the reaction conditions on the optical yield has been investigated for some substrates. 

Bigot S, Lai J, Suisse I, Sauthier M, Mortreux A, Castanet Y (2010) Telomerisation of 1,3-butadiene with glycerol under aqueous biphasic conditions influence of the reaction conditions on the products distribution. Appl Catal A Gen 382 181-189... 

Sitohy, M., Chobert, J.-M., and Haertle, T. 1994. Influence of the reaction conditions on the chemical phosphorylation of milk proteins. Milchwissenschaft 49, 610-615. 

S expresses, in a synthetic manner, the influence of the reaction conditions on the overall selectivity. This information is essential for studying the flexibility of design. Note that the number one in the last reaction is just convention we assume that the whole amount of free chlorine must be consumed in the last reaction, for which the real selectivity is of 1—(0.5 + 0.2) = 0.3. 

Aramendia, M. A., Borau, V., Garcia, I. M., Jimenez, C., Marinas, J. M. and Urbano, F. J. (1999) Influence of the reaction conditions and catalytic properties on the liquid-phase hydrobromi-nation of bromobenzene over palladium supported catalysts activity and deactivation. Appl. Catal. B Environ. 20, 101-110. 

A rare earth metal-exchanged Y-type (REY) zeolite catalyst was found to be an effective catalyst for the catalytic cracking of heavy oil. The influence of the reaction conditions and the catalytic properties of REY zeolite on the product yield and on gasoline quality have been described above. In this section, a reaction pathway is proposed for the catalytic cracking reaction of heavy oil, and a kinetic model for the cracking reaction is developed [14,33]. 

The CHDs formed by intramolecular addition often eliminate water to give another of,)6-unsaturated ketone. For mesityl oxide (4-methyl-3-pentene-2-one), 22b, the influence of the reaction conditions on the product distribution was examined in detail [96]. Mixtures of four dimeric species were observed, resulting from initial 4,4 -coupling (24b-d), or from mixed 2,4 -coupling, 24a. Pinacol formation (2,2 -coupling) was not observed [Eq. (6)]. 

The influences of the reaction conditions are demonstrated by means of results of measurements with the technical-grade sample D. Comparison of the hydrochlorination results at 340 °C, (Fig. 6), and 420 °C, (Fig. 7), shows considerable differences in the by-product formation and, consequently, in the trichlorosilane selectivity. At 420 °C the trichlorosilane selectivity is markedly lower and decreases continuously with time on stream, reaching values less than 40%. Silicon tetrachloride has been obtained in nearly complementary amounts to trichlorosilane, it being the major byproduct. 

Bonache MA, Gerona-Navarro G, Martfn-Martfnez M, Garcra-Lopez MT, Lopez P, Cativiela C, Gonzilez-Muniz R (2003) Memory of chirality in the enantioselective synthesis of P-lactams derived from amino acids. Influence of the reaction conditions. Synlett 7 1007-1011... 

In addition to the effects of different catalysts on the hydroxylation reaction, which are still discussed controversially in the literature [16], the knowledge of the influence of the reaction conditions, especially temperature and reactant partial pressure, is also important. In this paper detailed reaction engineering investigations with a H-Ga-ZSM5 are hence presented [5-7]. 

The influence of the reaction conditions on the conversion and selectivity is studied by ethylbenzene oxidation. Methanol leads to higher conversion than ethanol under the same... 

A linear model was adapted for determining the influence of the reaction conditions on the selectivity. The Cul-concentration does not affect the selectivity of the reaction, while an increase in the Pd(PPh3)2Q2-concentration reduces significantly the selectivity. The selectivity decreases slowly with time, since the product 5 reacts slowly to minor amounts of side products. The selectivity decreases also slighdy with increasing temperature and increasing excess of acetylene 2. 

One focus of the book is the hydroformylation process, the process involved in the first commercial implementation of aqueous-phase catalysis with its detailed descriptions of fundamental laws, special process features, and the present state of the art. Further focal points of the book are basic research on the complex catalysts (central atoms, ligands) and on the influence of the reaction conditions, solvents, and co-solvents, and a survey of other aqueous two-phase concepts and of proposed applications, with experimental examples and details. Environmental aspects are also considered. 

Influence of the reaction conditions (pH, temperature, concentration of substrates, organic solvent/cosolvents) on the reaction system and on the equilibrium constant,... 

This example is very instructive in that it demonstrates methods to suppress a non-desired reaction. The investigation of the reaction system leads to the question of the influence of the reaction conditions on selectivity. 

During the last 25 years a variety of processes have been developed for the thermal degradation of tyres in order to recover valuable components from rubber wastes.120-125 Stirred tanks, rotary kilns, fixed beds, fluidized beds and tray systems are examples of reactor types used for the thermal degradation of tyres. Several of these processes are now being used on a pilot plant and industrial scale. Basically, three fractions are derived from the thermal decomposition of tyres gases, liquid oils and solid residues. In the past, the influence of the reaction conditions and the reactor type were studied in order to maximize... 

The influence of the reaction conditions (pressure, temperature and inlet space velocity) are illustrated in Figures 8, 9 and 10, respectively. The pressure favours the synthesis of alcohols (methanol and H.M.A.) much more than that of hydrocarbons, irrespectively of reaction temperature. 

The geometric and promoter effects on the selectivity to furfuryl alcohol were studied in the hydrogenation of furfural over various series of platinum catalysts. The results obtained with the PtCu catalysts indicate that the size of the active site does not affect the selectivity. Promotion of the platinum catalyst can lead to a considerable rise in the selectivity to furfuryl alcohol. The hydrogenation over the series of PtSn catalysts showed the influence of the reaction conditions. The experiments under isothermic conditions resulted in up to 80% selectivity for furfuryl alcohol, while the selectivity dropped to approximately 40% if non-isothermic conditions were applied. This change in selectivity is attributed to the self-poisoning of the catalyst at high temperatures. 

Quantum chemistry has estabhshed itself as a valuable tool in the studies of polymerization processes [25,26]. However, direct quantum chemical studies on the relationship between the catalyst structure and the topology of the resulting polymer, as well as on the influence of the reaction conditions, are not practical without the aid of statistical methods. We have to this end proposed a combined approach in which quantum chemical methods are used to provide information on the microscopic energetics of elementary reactions in the catalytic cycle, that is required for a mesoscopic stochastic simulations of polymer growth [25]. A stochastic approach makes it possible to discuss the effects of temperature and olefin pressure. 

We have presented a comprehensive review of our recent theoretical studies on the polymerization and copolymerization processes catalyzed by the late transition metal complexes. The results of these studies show that a combined DFT/stochastic approach can be successfully used to model the elementary reactions in the polymerization processes and the influence of the reaction conditions on the polyolefin branching. Such an approach makes it possible to understand the microscopic factors controlling the branching of polyolefins and explain the differences between the Pd- and Ni-catalysts. The results also demonstrate that a wide range of microstructures can be potentially obtained from the ethylene polymerization. Thus, a rational design of the catalyst producing the desired polymer topology should be possible. 

The complex mechanism and the various processes (Fig. 10.17) are responsible for the strong influence of the reaction conditions and parameters. Additives play an important role. Thus the performance of different catalysts can be improved by (defined) small amounts of oxidizing as well as reducing agents [64, 143, 172], by a variety of additives (in particular by alkylammonium halides) and is strongly influenced by the nature of solvent and base. Note, that these parameters also influence the Pd leaching in an analogous manner. In particular for the activation... 

The influence of the reaction conditions at which the fuel cell is operated the dynamics of the solution phase present at the metal surface the influence of the carbon support on the metal and the solution phase and the size, shape and morphology of the supported nanoparticles that are used can all significantly alter the performance of these material. The influence from these extrinsic factors are critical and will likely be a significant focus of the future efforts from the theory community. 

Cyclobutanes.—Condensation of 1,3-dibromobutane with alkaline salts of phenyl-acetonitrile is syn-stereoselective in media of low dielectric constant. The influence of the reaction conditions on the ratio of product (172a) and (172b) has been examined in some detail and it has been reported that a similar reaction with 1,2-dibromopro-pane affords 2-methyl-1-phenylcyclopropyl cyanides. ... 

The influence of the reaction conditions were investigated using crotyl esters 106 of protected amino acids (R = CH3) (Scheme 5.2.29) [57]. The results are summarized in Table 5.2.9. In general, the syn products 107 were obtained preferentially in aU cases, but the relative ratio varied dramatically. 

The structure of the sol-gel silicate depends on the relative rates of the hydrolysis and condensation reactions, as well as on the reverse reactions [Eqs. (5.25)-(5.27)]. The influence of the reaction conditions on the mechanism and kinetics of the reactions forms a key issue in understanding the structural evolution. 

Yen, G.C. Lii, J.D. Influence of the reaction conditions on the antimutagenic effect of Maillard reaction products derived from xylose and lysine. J. Agric. Food Chem. 1992a, 40, 1034-1037. 

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