Factors influencing reactivity determinants

Evaluation of experimental data from work covered in Section 4.1 tends to confirm this concludion. These data indicate that, for quiescent clouds, both the scale and strength of a blast are unrelated to fuel quantity present in a cloud. These parameters are, in fact, determined primarily by the size and nature of partially confined and obstracted regions within the cloud. The factor of reactivity of the fuel-air mixture is of only secondary influence. 

The rates of addition to the unsubstituted terminus of monosubstituted and 1,1-disubstiluted olefins (this includes most polymerizable monomers) are thought to be determined largely by polar Factors.2 16 Polymer chemists were amongst the first to realize that polar factors were an important influence in determining the rate of addition. Such factors can account for the well-known tendency for monomer alternation in many radical copolymerizations and provide the basis for the Q-e, the Patterns of Reactivity, and many other schemes for estimating monomer reactivity ratios (Section 7.3.4). 

We make comparisons based on these data in very broad terms. Looking first at protonation, represented in Figure 5.7 by circles, we see that reactivity rises sharply with substitution from ethene to propene to 2-methylpropene, but 2-methyl-2-butene and 2,3-dimethyl-2-butene have rates roughly similar to 2-methylpropene. The degree of substitution at the more-substituted carbon is the major factor in reactivity. We can surmise from this trend that carbocation stability is the major factor in determining the protonation rates. Note also that styrene is more reactive than propene, again consistent with carbocation stability as the major influence on reactivity. In terms of the Hammond postulate, the carbocation is a good model of the TS because the protonation step is substantially endothermic and the TS is late. 

From the earlier discussion on the nature of the transition state for E2 reactions, two salient factors affecting reactivity can be recognised, these being polar and steric effects. The polar effect can be divided into inductive and conjugative or electromeric components . The influence of a substituent will depend principally on the nature of the transition state, which to a large extent is determined by the leaving group and the base and solvent. A reaction... 

Poly(ADP-ribose) polymerase itself is one of the major acceptors of poly(ADP-ribose) residues under conditions of DNA fragmentation in vitro (1) and in vivo (2, 3). For a better understanding of the involvement of polymerase in alterations of chromatin stmcture and function it is important to know the absolute content of the enzyme under varying conditions. Because of the multiple factors influencing polymerase activity, determination of the content via activity is not reliable. We have developed a procedure for immunoquantitation of poly(ADP-ribose) polymerase from TCA precipitates. In this way artifactual degradation can be avoided. When applied in conjunction with Western blotting, the procedure also allows the analysis of isoforms of the enzyme present in vivo, and reactivation experiments on SDS gels from the same sample. 

Some fundamental aspects of equilibrium and non-equilibrium phase equilibria have been discussed, along with the major factors that influence reactivity in the solid state. These topics are of crucial importance in ceramic technology and must be addressed in spite of their complexity and the considerable time, effort, and expense required to perform meaningful experiments. They impact on the entire range or relevant science and engineering from synthesis to sintering and final determination of the material s properties. 

The solvation of X is of course an extremely important factor influencing the reactivity of X in solution. Edwards and Pearson (1962) have noted that the charge distribution as calculated by quantum mechanics of an anion F is almost the same as in HF. Thus they conclude that the basicity is determined largely by the initial charge distribution in the base. A fluoride ion is much more basic than the large iodide ion in the gas phase and in solution because in fluoride the same amount of charge is concentrated in a much smaller space. 

Formation of a hydridoallyl complex in this manner increases both the oxidation state and the coordination number of the metal by two and, thus, reactivity is determined by the same factors as those that influence reactivity towards oxidative addition of simple substrates. 

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