Multi-step operations

Plutonium pyrochemical processes are now the principal tools at Los Alamos for producing large amounts of high purity plutonium metal from impure metal and oxide scrap. Pyrochemical processing was selected because of its cost effectiveness. The processes are highly compact and require little floor space and manpower to operate. The processes are also operationally efficient in that one or two steps can be used to supplant multi-step operations found in the classical aqueous chemistry flow streams. The... 

A general idea related to the preparation of protein-like copolymers through the co-polymerization or co-polycondensation of the mixtures of comonomers with differing hydrophilicity/hydrophobicity has been described in Sect. 2.1. Scheme 4 demonstrates the multi-step operations used in the first successful realization [26,27] of such an approach in a free radical polymerization process. 

Despite the rich chemistry of 45 [18], the only method for accessing this compound is the oxidation of the corresponding alcohol derived from 2-methyl-2-propen-l-ol or other sources, which can be obtained through multi-step operations. In contrast to the known methods, 45 can be readily derived from 44 and 50 by a simple one-pot operation. Since the propargylic alcohol 50 a is readily accessed from a ketone or aldehyde, realization of the transformation of 50 to 45 through a one-pot procedure provides a novel method for carbonyl olefmation of ketones or aldehydes. 

Domino reactions attract significant attention due to their ability to allow for multi-step operations in one pot. Two classes of domino transformations are known for the PK reaction. The first involves the use of a dual-catalyst system, while the second uses a single catalyst with modification of the reaction parameters to control reactivity. 

Beeause the processing of natural substances often involves multi-step operations, costs arc generally considered to be higher than a majority of synthesized compounds. A number of natural flavors and essences are given in Table 2. which illustrates the very wide range of ingredient... 

The truly innovative nature of the EniChem process over earlier ones is apparent. The preparation of hydroxylamine in the latter case necessitates multi-step operation, often ending with major co-production of inorganic salts, as in the Raschig process. The ammoximation of cyclohexanone, with its in situ generation of the intermediate, reduces significantly the investment and operahon costs while improving the environmental compahbility. The new process represents a good example of how to combine profitability and environmental concern. 

On the other hand, the manufacture of the TV screen is a multi-step operation The lithographic procedure has to be repeated for each of the three colours separately and in some cases an extra step is necessary in order to generate a non reflecting matrix pattern around the colour dots The colour dots are produced on the screen by flow... 

Process A Genetic instability Substrate repression Multi-step synthesis Product (volatile) inhibition Mode of operation Batch Fed-batch Continuous... 

The one-pot multi-step enzymatic process described above seemed still impractical on an industrial scale due to the low amount of 2 -deoxyribonucleoside accumula-hon and the low molar yield to added nucleobase (yield to adenine was 33.3%). In addition, it required three kinds of catalyst cells (baker s yeast, deoxyriboaldolase-or phosphopentomutase-expressing E. coli and commercial nucleoside phosphory-lase). It is difficult and complicated to operate the multi-catalysts. If the molar yield of 2 -deoxyribonucleoside to the most expensive material, nucleobase, was improved and the number of catalysts could be reduced, a practical enzymahc process could be developed. 

As an alternative to the classical mechanism shown in Scheme 29, a multi-step mechanism involving an electron donor-acceptor complex and a radical pair is shown in Scheme 30122. The distinction between the two mechanisms is difficult to make122-125. They can compete in forming the reaction products the idea that only one reaction pathway is operating, is an oversimplification. However, two relevant points cannot be disregarded ... 

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