Principal reaction pathways

Maleimides have three principal reaction pathways. These are radical addition to vinyl compounds the Michael addition with compounds having active hydrogens and the Diels-Alder reaction with dienes (Fig. 3). Any of the three can be tools for forming thermosetting adhesives. 

The principal reaction pathways proposed for the heterogeneous HDN of the model substrate (110)232-242 are shown in Scheme 45. A similar sequence of steps has also been suggested to occur for the HDN of (107). 

On the basis of the data obtained from the early thermal analysis and tube furnace pyrolysis experiments performed during the initial phases of this investigation, it became apparent that in order to establish the principal reaction pathways to the generation of volatile antimony species, the volatile degradation products of the DBDPO itself would need to be characterized (24, 25). 

Fahey (16) suggests that intermediate 3 dissociates formaldehyde he finds supportive evidence in the rhodium-based system by observation of minor yields of 1,3-dioxolane, the ethylene glycol trapped acetal of formaldehyde. For reasons to be discussed later, we believe the formation of free formaldehyde is not on the principal reaction pathway. (c) We have also rejected two aspects of the reaction mechanism proposed by Keim, Berger, and Schlupp (15a) (i) the production of formates via alcoholysis of a formyl-cobalt bond, and (ii) the production of ethylene glycol via the cooperation of two cobalt centers. Neither of these proposals accords with the observed kinetic orders and the time invariant ratios of primary products. 

The elimination of HO2 from the alkylperoxy radicals is the principal reaction pathway for the R + O2 reactions at temperatures above the transition region. (From Taatjes, 2006)... 

It is now well recognised that the active species is a cationic complex, or more precisely a solvent-separated or tight ion pair, the structure of which depends on the mode of catalyst activation. Early spectroscopic and synthetic studies on metallocene dimethyl precursors helped to outline the principal reaction pathways, these have been reviewed [16, 21, 23]. Some of this chemistry is briefly summarised here since it presents the background for the understanding of later studies on methyl-aluminoxane (MAO) systems. 

The photoreactions of thiirans have not been examined in as much detail, although the topic has been the subject of a comprehensive review.107 Ring cleavage and loss of sulfur is the principal reaction pathway ethylene, for example, is the major product of direct and benzophenone-sensitized... 

Figure 2. The thermodynamic situation upon solidification of a multemary system. The vertical lines designate principal reaction pathways, the dashed tangent lines illustrate the compositional changes arising from an equilibrium solidification at the respective pathways (interrupt lines on the vertical arrows). The narrow areas of existence designate stable phases with a finite phase width, the area designated metastable indicates the existence of a single phase solid which is unstable at ambient conditions.

How a particular vinylcyclopropane will be electronically perturbed toward a specific mode of reactivity depends on the substitution of either the cyclopropane or the vinyl portion. All of the principal reactions of vinylcyclopropanes proceed via transition states that require stabilization by activating groups and/or release of the ring strain. To understand and to alter the reactive tendencies of substituted vinylcyclopropanes, we must understand the components of the possible transition state and the probable reactive intermediates involved. Table 1 shows the principal reaction pathways of the vinylcyclopropane system in the context of their intermediates, products, and alkenic equivalents. 

It is interesting to note, that in the alkylation of phenol with isobutene, a change in temperature seems also to change the course of the alkylation reaction with the polysiloxane based catalysts. The principal reaction pathways to the main substitution products (according to the theory for electrophilic substitution, only very small amounts of meta-alkylation products are observed) are given in fig. 5. 

Figure 4.3 Principal reaction pathways for the zeolite-catalysed alkylation of phenol.

Atmospheric Chemistry of Hydrocarhons. Hydrocarbon compounds that are released into the troposphere are oxidized by a series of chemical reactions initiated by one or more of a variety of free radicals, such as OH, O3, and NO3. The principal reaction pathways are illustrated in Figure 1. An excellent review of the chemistry summarized in this figure has been... 

The oxidation of one mole of o-mannose by lead tetraacetate in acetic acid, which involves rapid reduction of 2.8 molar proportions of oxidant, is consistent with a principal reaction pathway in which the pyranose is degraded stepwise 4-(9-formyl-D-arabinose (76 77) is produced first, further oxidized to... 

In order to verify the geochemical changes along the Bahnbriicke transect, a reactive transport model was conceptualised and implemented. This model describes a onedimensional reactive transport along a streamline leaving the Oder riverbed into the deeper parts of the adjacent aquifer. The reactive transport model considers primary, and secondary redox reactions as well as precipitation/dissolution reaction. The principal reaction pathways as outlined by van Cappellen and Wang (1996) are given below. 

Returning to the manufacture of vinyl chloride, the principal reaction pathways are as follows. 

Although the detailed mechanism of the SchoU reaction remains elusive, two principal reaction pathways have been proposed, namely, the radical cation and... 

Oxy radicals (RO) are important intermediates in all VOC oxidation chains. They are formed in the chain propagating channels of the reactions of RO2 radicals with NO and in the self-reactions of RO2. Three principal reaction pathways for RO radicals have been identified under atmospheric conditions ... 

There was, however, a niggling problem with such a rationalization, which is outlined in Scheme 7b. The stereochemical aspect of neighboring group participation, is (sometimes) twinned with the kinetic aspect termed anchimeric assistance 18). Thus, the reaction of 31 should proceed through a dioxolenium intermediate 32 en route to the trans product. This assistance should be optimal for a trans-1,2 donors such as 22 and 25, and should cause them to react faster than the armed counterparts 21 and 24. Self-coupling of 22 and 25 should therefore have been the principal reaction pathways ... 

Principal Reaction Pathways for Fatty Acid Peroxides.26... 

PRINCIPAL REACTION PATHWAYS FOR FATTY ACID PEROXIDES... 

Equation 9 can be made the principal reaction pathway and Johnson and Nidy ( ) have reported a convenient and synthetically useful preparation of dialkyl peroxides using benzene as solvent and solubilizing the KO2 with crown ethers. Alcohols were frequently formed as by-products, probably resulting from reduction of the dialkyl peroxides with 02 (13). 

The rate law is first-order in both oxidant and reductant with an inverse term in hydrogen-ion concentration. The results of an 0 tracer study indicate that the principal reaction pathway involves a two-electron oxygen-atom transfer from the oxidant to the reductant. 

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