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Primary interactions

The effect of aromatic substrates on the formation of N02" is shown in the considerably increased substrate selectivity over that obtained with NO2+ salts. On the basis of the experimental data it is suggested that in these nitrations a weaker nitrating species than NO2+ must be involved in the primary interaction with the aromatic substrates. This incipient nitronium ion then attaches itself to the aromatics in a step giving high substrate selectivity. Whether the incipient nitronium ion is the nitracidium ion (H2NO3+), protonated acetyl nitrate (CH3COO—HN02 ) or probably a transition state of any of those unstable species to N02, in which water is loosened, but not yet completely eliminated, is difficult to say and no direct physical evidence is available. [Pg.71]

The primary interaction of singlet oxygen, produced by energy transfer from the excited sensitizer, with the diene can give rise to an exciplet that then collapses to peroxide, to a 1,4-biradical or to a 1,4-zwitterion alternatively, the adduct is the result of a concerted action without the involvement of an intermediate. Detailed kinetic Diels-Alder investigations of singlet oxygen and furans indicate that the reactions proceed concertedly but are asynchronous with the involvement of an exciplex as the primary reaction intermediate [63]. [Pg.169]

Some biomarker responses provide evidence only of exposure and do not give any reliable measure of toxic effect. Other biomarkers, however, provide a measure of toxic effects, and these will be referred to as mechanistic biomarkers. Ideally, biomarker assays of this latter type monitor the primary interaction between a chemical and its site of action. However, other biomarkers operating down stream from the original toxic lesion also provide a measure of toxic action (see Figure 14.3 in Chapter 14), as, for instance, in the case of changes in the transmission of action potential... [Pg.84]

Characterizing the radiation dose to persons as a result of exposure to radiation is a complex issue. It is difficult to (1) measure internally the amount of energy actually transferred to an organic material and to correlate any observed effects with this energy deposition and (2) account for and predict secondary processes, such as collision effects or biologically triggered effects, that are an indirect consequence of the primary interaction event. [Pg.306]

The primary interaction between RCRA and EPCRA is that some RCRA TSDFs treating hazardous waste are required to submit annual reports to U.S. EPA of their releases of chemicals to air, land, and water.2... [Pg.474]

Even in reactions involving excited states or in reactions between two radicals, the primary interaction which determines the reactivity is thought to proceed adiabatically. The probability of nonadiabatic charge transfer also may not be ignored between a molecular specie with small ionization potential and a specie with large electron affinity, in particular in the form of free, gaseous, or nonsolvated state. In that... [Pg.55]

Starting from the point of view of discrete molecules there are four frontier orbital and two primary interactions. The first... [Pg.65]

A second monoclinic polymorph of anilinium picrate has been found, showing a three-dimensional hydrogen-bonded polymer with strong primary interactions between the proximal phenolate and adjacent nitro groups and separate anilinium... [Pg.269]

The primary interaction occurring during a photochemical process is between light and an analyte, such as a molecule, ion, atom, etc. The reaction is often written in the generalized form... [Pg.426]

The dipole orientation condition is questionable but is supported by other studies on H-F coupling constants. The selection of the reaction field as the primary interaction is also somewhat questionable. Few investigators actually correlated results with the mathematical expressions for the reaction field. [Pg.159]

LSR, nitrogen, the more basic of the heteroatoms, appeared to be the site of primary interaction. This conclusion was simultaneously corroborated by the nonequivalence behavior of several configurationally established oxaziridines reported independently by two groups (41,42). These oxaziridines were prepared by peracid oxida-... [Pg.291]

A careful choice of washing solvents can produce extensive sample clean up . The elution solvent must overcome both the primary interactions of the analyte with the bonded phase and any secondary interactions with silanol groups. [Pg.326]

Ionizations produced by electrons generated in the primary interaction of the incident fast charged particle are called secondary. The definition may be extended to all successive generations if sufficient energy is available. In this sense, secondary ionization is very... [Pg.23]

The most common secondary messengers in signal transduction pathways, formed from the primary interaction, are calcium ions (Ca ). The receptor-hormone complex induces changes in the cell s metabolism, usualfy by affecting transcription or translatioiL... [Pg.127]

The interaction of metal atoms with monoalkenes has been investigated on both a spectroscopic and preparative scale. It appears that the primary interaction between a metal atom and an alkene at low temperature is the formation of a ir-complex. This may subsequently lead to a thermally stable 7r-alkene complex or to rearrangement products by hydrogen abstraction or reaction with another alkene moiety, depending on the electronic requirements of the metal and the particular alkene considered. [Pg.59]

The primary interaction of radiation with matter leads to the formation of positive ions and excited molecules. Thus, in a medium constituted of molecules of a substance AB, the primary radiation-chemical events can be written ... [Pg.33]

If Figure 3.9a represents bond formation between two molecules, the reverse process would correspond to heterolytic bond cleavage. One notes, however, that in the gas phase heterolytic bond cleavage is never observed. As we shall see, the interaction depicted in Figure 3.9a is the primary interaction between any pair of molecules whether it leads to bond formation or not. It is responsible for van der Waals attraction and hydrogen bonding. [Pg.50]


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See also in sourсe #XX -- [ Pg.39 ]




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