Multi reactions

P 40] A similar protocol was made for the 2x2 multi-reaction mode. Using a special script to guide flow over 700 or 1000 s, depending on the individual reaction, a residence time of 120 s was achieved for each reaction. The other features of the protocol are identical with ]P 39]. 

OS 57] [R 6] [P 40] One of the first examples of parallel multi-reaction was performed in a Caliper chip [18], By 2 x 2 combinations of two aldehydes and two 1,3-diketones, four cycloadducts were generated simultaneously in one run on one chip (Figure 4.71). The conversions were comparable to those for the single runs, with one exception. Also, cross-contamination was observed. It ranged from a few percents to about 50%. It should be pointed out that despite these initial drawbacks the demonstration of multi-reaction feasibility is a further valuable step in micro channel processing. 

In the synthesis of acidic peptide such as BMP, aspartic acid and glutamic acid residues were stepwisely elongated. In case of the practical synthesis of peptide containing a many acidic amino acid residues, multi reaction procedure for long duration may be required. 

V. Balakotaiah and D. Luss. Analysis of multiplicity patterns of a CSTR. Chem. Eng. Commun. 13, 111 (1981) 19, 185 (1982). See also these authors papers Structure of the steady state solutions of lumped-parameter chemically reacting systems. Chem. Eng. Sci. 37, 43,1611 (1982) Multiplicity features of reacting systems. Dependence of the steady-states of a CSTR on the residence time. Chem. Eng. Sci. 38, 1709 (1983) Global analysis of multiplicity features of multi-reaction lumped-parameter systems. Chem. Eng. Sci. 39, 865 (1984). 

Balakotaiah, V. and Luss, D., 1984, Global analysis of the multiplicity features of multi-reaction lumped-parameter systems. Chem. Engng ScL 39, 865-881. 

For a pulse-type NMR experiment, the assumption has a straightforward interpretation, since the pulse applied at the moment zero breaks down the dynamic history of the spin system involved. The reasoning presented here, which leads to the equation of motion in the form of equation (72), bears some resemblance to Kaplan and Fraenkel s approach to the quantum-mechanical description of continuous-wave NMR. (39) The crucial point in our treatment is the introduction of the probabilities izUa which are expressed in terms of pseudo-first-order rate constants. This makes possible a definition of the mean density matrix pf of a molecule at the moment of its creation, even for complicated multi-reaction systems. The definition of the pf matrix makes unnecessary the distinction between intra- and inter-molecular spin exchange which has so far been employed in the literature. 

A Novel Method for Determining the Multiplicity Features of Multi-Reaction Systems... 

We have used this technique to determine the qualitative features of several multi-reaction systems and the results will be reported elsewhere [1,2]. It is expected that this method will become the standard tool for predicting the qualitative multiplicity features of these systems. 

Figure 25. A multi-reaction system for decomposition of water ...

The first order division is based on the system with or without reaction coupling, so the modern thermodynamics in a broad sense has been divided into the classical thermodynamics and the modem thermodynamics in a narrow sense. It is very clear that classical thermodynamics should only be used for simpler systems without reaction coupling, because the second law of thermodyneimics, such as dG)r,p 0, is only concerned with the whole system and not concerned with individual processes. That is a severe limitation of classical thermodynamics, because systems in modem inorganic synthesis and in life science are usually complex with multi-reaction processes including reaction coupling. 

The superposition model was also applied for the pyrolysis of washed wheat straw, where a multi-reaction model is required to fit the data. Experiments show that the DTG-curves have two distinct peaks, which makes the kinetics determination easier than for raw straw. Fig. 9 shows the fit of three reactions to the mass loss rate data from the pyrolysis of... 

Multienzyme modular assemblies such as PKSs and NRPSs have flexible swinging tethers which channel covalently bound intermediates between successive active sites. Swinging arms plus specific protein-protein interactions offer mechanisms for the transfer of substrates between modules and offer concepts for the development of one-pot multi-reaction biocatalytic processes. 

Finally, Nyffeler and co-workers (18) have modelled radiocesium uptake by marine sediments, using a multi-reaction model with an irreversible process similar to that in the 2- and 3-box models of Fig. 5. These authors have also obtained a similar rate of... 

A multi-reaction experiment has been successfully carried out in a single chip reactor to obtain four different cydoadducts from the combinations of two different 1,3-dicarbonyl compounds and two different aldehydes. 

In multi-reaction systems, economical optimality implies high selectivity. This can be achieved at low per-pass conversion operating points that might be unfeasible due to the low-conversion instability. 

Reactions that succeed the hydroformylation can be conducted in a separate step by using entirely different reaction conditions. Alternatively, a multi-reaction sequence can be performed in one pot by using the same reaction regime or different ones. Such transformations belong to domino reactions, multicomponent reactions, or tandem reactions. Especially in the last years, tandem reactions came in the focus of synthetic chemists. In the best case, a single catalyst mediates not only hydroformylation but also the other reactions, and we can call it auto tandem catalysis due to a suggestion by Fogg and dos Santos [2]. 

Multi-reactant multi-reaction processes with non-linear kinetics... 

For multi-reactant / multi-reaction systems, state multiplicity occurs. The instability of the low-conversion branch restricts the selection of the operating point. 

A KDIE is observed only during the slowest step in a given chemical reaction or in the slowest chemical reaction of a multi—reaction process therefore, a KDIE defines the rate—controlling step of a chemical reaction or process ... 

Cascade Reactions. Cascade reactions can be defined as multi reaction one pot sequences in which the first reaction creates the functionality to trigger the second reaction and so on. Cascade reactions have also been termed tandem or domino processes by some authors. This section is concerned with Pd(PPh3)2Cl2- [to generate Pd(0)] or PdCl2-catalyzed processes in which two or more carbon-carbon/carbon-heteroatom bonds are formed. 

Here, there are 2F coulombs passed per mole of H2 (n = 2 eq electrons/mol H2). Note that it is possible that some purely chemical reactions can also occur in parallel with electrochemical reactions. In this case, the purely chemical component of the reaction must also be known to determine the relationship between charge passed and consumption or generation in the overall multi-reaction process. 

---