Secondary generic reactions

Figure 5.3. Sketch of the major processes proposed in cluster models of MALDI ionization. A, analyte m, matrix R, generic counterion. Preformed ions, separated in the preparation solution, are contained in clusters ablated from the initial solid material. Some clusters contain a net excess of positive charge, others net negative (not shown). If analyte is already charged, here by protonation, cluster evaporation may free the ion. In other clusters, charge may need to migrate from its initial location (e.g., on matrix) to the more favorable location on analyte (secondary reaction). For multiply charged analytes, hard and soft desolvation processes may lead to different free ions. Neutralization by electrons or counterions takes place to some degree but is not complete.

Schematic plots of the internal energy versus the reaction coordinate for both primary and secondary insertions and for generic aspecific, syndiospecific, and isospecific model complexes are sketched in Figures 1.11 a,b, and c, respectively. The minima at the centers and at the ends of the energy curves correspond to alkene-free intermediates, including a growing chain with n and n + 1 monomeric units, respectively. Movements from the central minima toward the left and the right correspond to possible reaction pathways leading to primary and secondary insertions, respectively. For the enantioselective complexes the reaction pathways for monomer enantiofaces being...

Humic substances A series of relatively high-molecular-weight, yellow- to black-colored substances formed by secondary synthesis reactions. The term is used as a generic name to describe the colored material or its fractions obtained on the basis of solubility characteristics. These materials are distinctive to the soil (or sediment) environment in that they are dissimilar to the biopolymers of microorganisms and higher plants (including lignin)... 

Hydrohalic acids can cause cleavage of the ether. Hydrofluoric acid, HF, doesn t work as well as the other acids in the group (HCl, HBr, or HI)-Secondary and tertiary ethers undergo reaction, while methyl and primary ethers undergo Sp 2 reaction. A generic example is in Figure 3-34, and the mechanism is in Figure 3-35. 

The [3-hydroxy amines are a class of compounds falling within the generic definition of Eq. 6A.6. When the alcohol is secondary, the possibility for kinetic resolution exists if the Ti-tartrate complex is capable of catalyzing the enantioselective oxidation of the amine to an amine oxide (or other oxidation product). The use of the standard asymmetric epoxidation complex (i.e., T2(tartrate)2) to achieve such an enantioselective oxidation was unsuccessful. However, modification of the complex so that the stoichiometry lies between Ti2 (tartrate) j and Ti2(tartrate)1 5 leads to very successful kinetic resolutions of [3-hydroxyamines. A representative example is shown in Eq. 6A.11 [141b,c]. The oxidation and kinetic resolution of more than 20 secondary [3-hydroxyamines [141,145a] provides an indication of the scope of the reaction and of some... 

Hydrocarbon autoxidation takes place via a complex set of radical reactions, some of which were only recently identified. One of the mechanistic difficulties is that the reactions can only be indirectly investigated by monitoring the evolution of stable products. The input of quantum-chemical calculations, in combination with theoretical kinetics, turned out to be a crucial tool to construct a generic mechanism. One of the new insights is the importance of the copropagation of the primary hydroperoxide product. A solvent-cage reaction, activated by the exother-micity of this secondary step, leads to the formation of the desired alcohol and... 

Table 3 Typical secondary generic reactions. Units mol, cm, s, kJ.

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