Stepwise process sequence

A variation of the selective Cu deposition process, limited to electroless Cu deposition, is the lift-ojfprocess, a planarized metallization process (16). Figure 19.5 shows a stepwise process sequence for this technology. 

For the discussion of the rearrangements in section III only stepwise reaction sequences will be considered. We must note, however, that many of these transformations may just as well result from concerted processes in accordance with the rules for orbital symmetry conservation,... 

The operation cycle is a stepwise process. The essential steps are filling the vessel, filtration (service), back-pulse (cleaning), cake settling, and sludge discharge. In practice, the steps will vary in length from application to application, but all working operation sequences include these basic steps, which will be addressed in order. 

Sequencing is a stepwise process of identifying the specific amino acids at each position in the peptide chain, beginning at the N-terminal end. Phenylisothiocyanate, known as Edman s reagent, is... 

An important a priori assumption of the kinetic irreversibility of any step of a stepwise process is that it may result in considerable errors in identifying both the rate limiting and the rate determining steps. Let us illustrate this statement with the preceding sequence of monomolecular reactions. If the kinetic irreversibility of all of the elementary reactions is a priori assumed, then the direct consequence of this statement is the fol lowing relationship ... 

The stability of the mixed-valent species Rn(IV)—Rn(III) and Ru(III)—Ru(II) can be at first determined by the separation of the respective oxidation or reduction sequences, i.e. the higher the separations between the two stepwise processes, the higher the stability of the mixed-valent systems. In all cases, bnt for those in which a single two-electron step was detected, the Ru(lV)—Rn(III) and Rn(III)—Rn(II) systems belong to the partially delocalized mixed-valent systems. 

From a standpoint of organic chemistry this representation cannot be really considered as a mechanism of the reaction, but is rather a description of a complicated stepwise process leading to the transformation of the initial chaos of C clusters into the highly ordered structures of Ceo and C70 fullerenes. It is assumed that thermodynamic control serves as the driving force over the sequence of these reversible and kinetically plausible steps. 

The synthetic sequence to methylene-bridged poly(phenylene)s 71 represents the first successful employment of the stepwise process to ladder-type macromolecules involving backbone formation and subsequent polymer-analogous cyclization. As shown, however, such a procedure needs carefully tailored monomers and reaction conditions in order to obtain structurally defined materials. The following examples demonstrate that the synthesis of structurally defined double-stranded poly(phenylene)s 71 (LPPP) via a non-concerted process is not just a single achievement, but a versatile new synthetic route to ladder polymers. By replacing the dialkyl-phenylenediboronic acid monomer 68 by an iV-protected diamino-phenylenediboronic acid 83, the open-chain intermediates 84 formed after the initial aryl-aryl cross-coupling can te cyclized to an almost planar ladder-type polymer of structure 85, as shown recently by Tour and coworkers [107]. 

The reactions of furansulfonyl chlorides with anilines (entry 11)123 in MeOH yield a linear Bronsted plot with fix =0.51, which indicates an Sw2 mechanism rather than a stepwise process. This value is quite similar to those found for the reactions of anilines with benzenesulfonyl chloride (0.63)117, with 2-thiophenesulfonyl chloride (0.53)124 and with 3-thiophenesulfonyl chloride (0.54)125. Thus their anilinolysis mechanism is also expected to be S/y2. The reaction rate therefore depends not only on the nucleophile basicity but also on the substrate reactivity. Comparison of the reaction rates leads to the following reactivity order for the Ar moiety benzene > 3-thiophene > 3-furan > 2-furan > 2-thiophene. This reactivity sequence follows the order of the resonance interaction between the... 

Herein, we expand on the discussion of our recently observed isothermal amorphous-amorphous-amorphous transition sequence. We achieved to compress LDA in an isothermal, dilatometric experiment at 125 K in a stepwise fashion via HDA to VHDA. However, we can not distinguish if this stepwise process is a kinetically controlled continuous process or if both steps are true phase transitions (of first or higher order). We want to emphasize that the main focus here is to investigate transitions between different amorphous states at elevated pressures rather than the annealing effects observed at 1 bar. The vast majority of computational studies shows qualitatively similar features in the metastable phase diagram of amorphous water (cf. e.g. Fig.l in ref. 39) at elevated pressures the thermodynamic equilibrium line between HDA and LDA can be reversibly crossed, whereas by heating at 1 bar the spinodal is irreversibly crossed. These two fundamentally different mechanisms need to be scrutinized separately. 

Two idealized mechanistic scenarios for electron deficient [1,2] alkyl shift reactions can be envisaged a concerted event, in which alkyl migration is essentially synchronous with carbocation formation and a stepwise process, involving initial formation of a discrete cationic species followed by subsequent alkyl migration. Of the two, the concerted scheme is intuitively associated with a lower activation barrier. It should be noted that these sequences clearly represent extreme positions of a continuum of substrate and condition dependant mechanistic hybrids. With a view toward developing a predictive sense for the [1,2] alkyl shift, these mechanistic issues are relevant, in that the specific migrating bond for a given substrate will be influenced... 

Polypeptides with single monomer units, however, are not of primary interest for study of the biological aspects of peptides and proteins. What is of interest in the biological realm is a specific sequence of monomer units chosen from the twenty-some amino acids found in natural proteins. Peptide or protein synthesis, therefore, is usually a stepwise process each specific monomer unit must be added in proper sequence. 

Packaged units have traditionally had their own progranunable logic controllers (PLCs) and local control panels. This is especially true in the case of units that require extensive sequence controls for stepwise processes such as filtration and ion exchange. Many operators find it more convenient to have control supervised from a central station. From this point of view, these systems are better controlled by a distributed control system (DCS) and monitored from the control room. Some who bought systems equipped with PLCs some years ago have dispensed with the PLCs and moved control to the DCS. Many favor systems which combine local control by PLC with status and alarm signals sent to the DCS. 

The HORNY LAYER is the product of epidermal differentiation. A series of gene-controlled structural proteins and enzymes have to interact in a well-defined sequence. Keratinization will be impaired and the end product imbalanced if one or another of the gene products or the regulation of the stepwise process is lacking or faulty. 

---