Reactivities, significance

The relative chemical inertia of the C-0 bond has already been emphasised. Structural factors can increase this reactivity significantly. This can lead to ruptures that can be dangerous in certain situations. In this case, the higher propensity of this bond to rupture makes the particular ether rather unstable. The following table gives the enthalpies of decomposition for a few ethers. 

In other words, the butadiene monomer reactivity significantly differs from isoprene but by a smaller factor than for a styrene-diene system. Nevertheless, the phenomenon of "reversal of... 

Reactivity significantly greater than the transition metals, akin to group 2 elements. 

Most 1,3,5-trithianes are active co-initiators in benzophenone-induced polymerization. The most efficient is /i-TMT, whose reactivity significantly exceeds that of the a-isomer. Consideration of the order of the quantum yields (Table 12) suggests... 

Absolute Reactivity.—Significant interest has continued to be shown in the question of absolute reactivity in cationic propagations, and in particular in quantifying the contribution from free ion and ion-paired species. 

The present study deals with a characterization of the local structure of the Mo-oxides of Mo-MCM-41 and their photocatalytic reactivity, significantly for the decomposition of NO into N2 in the presence of CO by means of XAFS (XANES and EXAFS), XRD, ESR and in-situ photoluminescence measurements. 

Relatively low levels of air slaking can reduce the reactivity significantly. For example, 1.5 % of combined water, coupled with a smaller, but un-measured amount of re-combined carbon dioxide has been observed to reduce the BS 6463 reactivity from 60 to 50 °C. As a general rule, reactivity results for quicklime samples with combined water contents in excess of 1.0 % may not be valid. 

The concept that free radicals are important intermediates in photochemical and other redox interactions of oxygen, organic compounds and heavy metals in natural waters has received considerable support recently ((1-3) and references therein this volume). Some of the major primary radicals expected are hydroxyl (OH), superoxide (02 ). and various organic moieties (R, RO, ROO). Of these, OH is of interest because of its extremely high reactivity, significant formation rate from a known source (nitrite photolysis, among others) and the analogy of its known key role in tropospheric chemistry. 

Due to the high number of unsaturated bonds that are still present in the end product after vulcanisation, the natural rubber is a chemically reactive compound. This reactivity significantly reduces the chemical compatibility and useful shelf life of natural rubber. 

To improve the characteristics of coordination polymerization catalysts, the combinations of different metal derivatives have been investigated. The association of zinc chloride to aluminum alcoholates improves the reactivity significantly and results in higher conversions (see Table 9). However, two polymer fractions are still obtained an isotactic and crystalline polymer of high molar mass and an amorphous and atactic polymer (mole fraction of isotactic dyads is less than 0.6). In contrast to AIR3/H2O or ZnR2/H20, the latter consists of regular head-to-head and tail-to-tail enchainments. ... 

Typical surfactants have a difference in valence of one electron relative to the atom they replace. Thus, As atoms passivate Si surfaces, while S atoms can be used to passivate GaAs. H treatment of a Si surface reduces its reactivity significantly and passivates surface states. However, H is a small atom and relatively weakly bound to the surface. Furthermore, it reacts readily with other atoms that may adsorb. Hence, H passivation is delicate and of limited long-term value. Of more significance is that H can fit into many vacancies in solids, will passivate their dangling bonds, and so reduces the number of electrically-active defects. This is one reason why many chemical vapor deposition crystal growth processes include copious amounts of H as a dilutant gas. It not only contributes to control of the deposition reaction process, but it helps reduce the effects of growth defects. 

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