The generator of acids

Fig. 20. Proposed photochemical mechanisms for the generation of acid from sulfonium salt photolysis. Shown ate examples illustrating photon absorption by the onium salt (direct irradiation) as well as electron transfer sensitization, initiated by irradiation of an aromatic hydrocarbon.

Decomposition of trichloroethylene can occur upon contact with naked flames, red-hot surfaces, hot elements of electric heaters, or intense UV light with the generation of acidic and highly-toxic products. The presence of reactive contaminants, e.g. acids, strong alkalis, highly-reactive metals, may also result in decomposition to similar products. 

Effects of Structural Disorder on the Generation of Acidic Sites in Zeolite L... 

In addition to the aluminosilicate systems, a wide variety of other binary metal oxides exhibit surface acidities and acid-catalyzed activities that are greater when the oxides are chemically combined than would be the case for a physical mixture of the same oxides. The existence of this type of synergism is most easily explained in terms of Pauling s electrostatic valence rules (135). In a recent paper, Tanabe et al. (136) have extended such rules to account for the generation of acidity in 26 binary oxides. They make two postulates ... 

To investigate the chemical functionality or the order of deprotection of the photoresist surface, the zeta potential of some chosen photoresist samples was measured in electrolyte solutions as a function of the pH value. It is shown in Fig. 6. In consequence of dissociation and adsorption processes at the surface the zeta potential decreases monotonically. The pH value at which the zeta potential function passes zero is called the isoelectric point (iep). Figure 4c shows the iep as a function of the exposure dose. It is shifted to smaller values if the exposure dose approaches the threshold value. This is caused by the generation of acid groups at the surface during processing (cf. Scheme 1). In the case of unexposed photoresist no functional groups exist at the surface. Ion adsorption processes... 

K Tanabe Solid Acid and Base Catalysts This chapter deals with the types of solid acids and bases, the acidic and basic properties, and the structure ofacidic and basic sites. The chemical principles of the determination of acid-base properties and the mechanism for the generation of acidity and basicity are also described. Howacidid and basic properties are controlled chemically is discussed in connection with the preparation method of solid acids and bases. 

The acid strength of the acid forms in the solid state usually reflects the one in solution, but the acidic properties of the salts in the solid state are more complicated in general. Five mechanisms are possible for the generation of acidity in metallic salts [5] ... 

Acid sites of AgjPW C are generated upon the reduction with hydrogen at 573 K [40,42], After the reduction, the catalytic activity (for example, for o-xylene isomerization) develops. The generation of acid sites has been confirmed by pyridine adsorption and solid state H NMR [42]. 

As a synthetic approach this reaction is valuable for the generation of acid bromides, acid iodides and acid fluorides. The readily accessible acid chlorides are a convenient starting material. Thus, it is possible to react acid chlorides with hydrogen fluoride, hydrogen bromide or hydrogen iodide to obtain the corresponding acid halides. ... 

Intramolecular photoinduced electron transfer (PET) may lead to the generation of acid (i.e., protons) from an anthracene-based sulphonium salt. An amphiphilic anthracene-based photoacid generator (An-PAG) has been synthesized and was reported to induce acid-catalyzed hydrolytic degradation of certain lipids upon UV exposure (Shum et al., 2001). At present, the application of this technique is limited by the short wavelength required to trigger the response. 

The maximum of pyridine desorption observed in TPD spectra (Fig.l) is a compilation of the desorption from sodium and the other alkali cations. In the case of Cs,NaY the degree of cation exchange is low, and, therefore the pyridine desorption from sodium cations influences strongly the position of the TPD band. The increase in the selectivity towards hydrocarbons on K,NaY in comparison with Cs,NaY (Fig.3) indicates that the acidic strength of cations showed by TPD maxima does not play the most important role in the formation of hydrocarbons. One should note that the generation of acidic hydroxyl groups as a result of the dissociative adsorption of H2S (ref.8) also influences the selectivity towards hydrocarbons. 

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