Yield, of chemical reactions

Margulis MA, Mal tsev (1968) Estimation of energetic yield of chemical reactions initiated by ultrasonic waves. II. Initial chemical acoustic yields of products of water decomposition by ultrasound. Zh Fiz Khim 42 2660-2663, Russ J Phys Chem (42) 1447-1451... 

Yields of Chemical Reactions 3.13 Determining Molecular Masses ... 

In optimization of the process of obtaining novocaine, FRFE 24"1 with generating ratio X XjXzXj was chosen for the basic design of experiments. The system factors are x,-time of reaction, min x2-temperature, °C x3-surplus of sodium salt of paraa-minobenzoic acid, % and X4-concentration of sodium salt of paraaminobenzoic acid, %. The system response is the yield of chemical reaction %. Outcomes of basic experiment with application of method of steepest ascent are shown in Table 2.191. 

Identification of segregation by chemical methods. Partial segregation can be studied through its influence on the conversion and yield of chemical reactions. For instance, let us denote by Xmacro and micro t ie limiting extents of reaction one would observe in a well macromixed reactor. If the reactor is partially segregated X = gXmacro + (1 - g) X. ... 

The effect of coalescence and break-up of droplets on the yield of chemical reactions was studied by Villermaux (33). Micromixing effects may occur even in batch reactors if there is a drop size distribution and mass-transfer control. Although practical rules for the design and scale-up of liquid-liquid reactors are available as Oldshue showed in the case of alkylation (152), many problems remain unsolved (.5) mass transfer effects, high hold-up fractions (> 20 %), large density differences, high viscosities, influence of surfactants. 

Micromixing phenomena are the processes whereby different chemical species which are supposed to mix and react are coming into contact at the molecular scale. The result of imperfect micromixing is local unhomogeneity of the reacting mixture and this causes differences in the conversion and yield of chemical reactions, especially when portions of the fluid having reacted at different instants are mixed together. Fast reactions, combustions, precipitations, polymerizations may particularly be affected by these phenomena. 

The actual yield of chemical reactions is usually less than the theoretical yield. This is caused by a variety of factors. For example, sometimes less than perfect collection techniques contribute to a lower than expected yield. 

The percentage yield of chemical reactions is extremely important in industrial chemistry and the pharmaceutical industry. For example, the synthesis of certain drugs involves many sequential chemical reactions. Often each reaction has a low percentage yield. This results in a tiny overall yield. Research chemists, who generally work with small quantities of reactants, may be satisfied with a poor yield. Chemical engineers, on the other hand, work with very large quantities. They may use hundreds or even thousands of kilograms of reactants A difference of 1% in the yield of a reaction can translate into thousands of dollars. 

This chapter develops the thermodynamic methods for predicting whether a reaction is spontaneous, and Chapter 14 uses these results to determine the equilibrium ratio of products and reactants. Chapter 18 discusses the rates of chemical reactions. Manipulating conditions to optimize the yield of chemical reactions in practical applications requires the concepts from all three chapters. 

Since on the surface of a porous carbonaceous material reactions occur in a confined nanospace, its dimensions and enhanced dispersive interactions can significantly change the chemical equilibrium [44,45], the yield of chemical reaction and its selectivity, and thus the efficiency of the reactor or catalytic process. 

Selectivity, Conversion, and Product Yield OF Chemical Reactions... 

The selectivity, conversion, and product yield of chemical reactions along with the power inputs, basically determine the practical availability of a chemical process. Definitions of these parameters may be found in [1-6],... 

This section describes numerical and experimental means for the detailed characterization of multiphase flows. Flow behavior is closely linked to the transport processes of fluid mixing and axial dispersion and therefore affects the yield of chemical reactions performed in microchannel networks. Integrated multiphase flow sensors are potentially important for observing and controlling microreactor performance during continuous operation. 

Surface-ionization mass spectrometry (SI-MS) studies of organic compounds show that in most cases the compounds decompose into radicals, which have a lower ionization energy IE) than the corresponding molecules, and are ionized more efficiently. For a given type of secondary species, s, formed on the surface, the resulting positive thermionic emission currents (/) and their dependence on surface temperature (7) are described by the ionization efficiency, Ps(7), and by YXT), the yield of chemical reactions on the surface, such that... 

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