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Cation chemical conversion

Thiocyanate can be recovered and recycled from this solution by the precipitation of iron as iron(III) hydroxide.366 Aurocyanide can also be eluted from a strong-base resin by chemical conversion of the gold to a cationic complex with the thiourea ligand, as shown above (equation 98). This method of gold elution is favoured in the Soviet Union, but suffers from the drawback that elution of the other metal cyanide complexes is generally poor, and multi-elution procedures are necessary. [Pg.823]

A number of biomimetic syntheses have included Wagner-Meerwein rearrangements. A chemical conversion of humulene (48) to sterpurene (50) involved an interesting series of Wagner-Meerwein rearrangements (see Scheme 19).- - Humulene (48) was converted to the cyclooctenol (51) and thence to the bromide (52) via the protoilludyl cation (49). Treatment of (52) with silver acetate in acetic acid gave racemic sterpurene (50). In contrast the epimeric bromide (53) gave (54). [Pg.714]

Two elements of the cyclization have yet to be addressed the isomerization of geranyl pyrophosphate to linalyl pyrophosphate (or the equivalent ion-pair) and the construction of bicyclic skeleta. Studies on the biosynthesis of linalool (61), and on the analogous nerolidyl system in the sesquiterpene series (52), have shown this allylic transposition to occur by a net suprafacial process, as expected. On the other hand, the chemical conversion of acyclic or monocyclic precursors to bicyclic monoterpenes, under relevant cationic cyclization conditions, has been rarely observed (47,62-65) and, thermodynamic considerations notwithstanding (66), bicyclizations remain poorly modeled. [Pg.141]

Anions participate in chemical conversions and in the total exchange dynamics in the soil to an essentially lesser extent than cations. The reason for this is that they are less adsorbed on the colloidal complex, since the soil adsorbents are negative rather than positive on their surfaces. The soil exchange capacity increases with the acidity for anions, which is connected with an increase of the positive charge of soil colloids, particularly of hydrated oxides. In cultivated soils of the Temperate Zone, with a pH... [Pg.658]

Figure 16.45. Schematic representation of the chemical corrosion of polypyrrole in three steps I, initial state 2, distribution equilibrium for nucleophiles 3, partial chemical conversion + radical cationic centre O nucleophiles in solution 9 nucleophile in the solid and reacted slates. Adapted from Werkstoffe und Korrosion 42, 341 (1991), with permission of VCH,... Figure 16.45. Schematic representation of the chemical corrosion of polypyrrole in three steps I, initial state 2, distribution equilibrium for nucleophiles 3, partial chemical conversion + radical cationic centre O nucleophiles in solution 9 nucleophile in the solid and reacted slates. Adapted from Werkstoffe und Korrosion 42, 341 (1991), with permission of VCH,...
Size press starch may be non-ionic, from in-mill enzymatic conversion or thermo-chemical conversion of native starch. It may be anionie if an oxidised starch is used. (Note this refers to chemically modified oxidised starch. Many American texts wrongly refer to any viscosity-reduced starch - including enzyme-converted and thermo-chetnically converted stareh - as oxidised stareh. Such processes do not form any carboxyl or carbonyl groups on the starch.) Furthermore, cationic and amphoteric starches are frequently tpplied on multi-purpose office paper for improved ink-jet printability. [Pg.191]

Chitosan fungi wall membrane (Mucor rouxil), commercially derived from chitin by chemical conversion with strong alkali 2-amino-2-deoxy-D-glucosc (D-N-glucosamine) in /I (1-4) linkage, cationic... [Pg.282]

Tropane alkaloids are found mainly in the Solanaceae [14] plant family. First biosynthetic step of tropane alkaloids starts with iV-methylation of putrescine (derived from L-omithine) to form Al-methylputrescine. After the conversion to 1-methyl-Al pyrrolinium cation, its condensation with nicotinic acid gives rise to nicotine synthesis, while other chemical conversions lead to the formation of tropinone, the precursor of many tropane alkaloids through branched pathways (Fig. 8.8a) [15]. [Pg.222]

Since multiple electrical and optical functionality must be combined in the fabrication of an OLED, many workers have turned to the techniques of molecular self-assembly in order to optimize the microstructure of the materials used. In turn, such approaches necessitate the incorporation of additional chemical functionality into the molecules. For example, the successive dipping of a substrate into solutions of polyanion and polycation leads to the deposition of poly-ionic bilayers [59, 60]. Since the precursor form of PPV is cationic, this is a very appealing way to tailor its properties. Anionic polymers that have been studied include sulfonatcd polystyrene [59] and sulfonatcd polyanilinc 159, 60]. Thermal conversion of the precursor PPV then results in an electroluminescent blended polymer film. [Pg.223]

A different strategy has been applied in our work, that emphasizes the importance of DNA stability on hole transfer within double-stranded DNA. This work is based on determination of the overall yield of oxidized nucleosides that arise from the conversion of initially generated purine and pyrimidine radical cations within DNA exposed to two-photon UVC laser pulses. On the one hand, this work benefits from the excellent current knowledge of chemical reactions involving the radical cations of DNA bases, and on the other hand, from major analytical improvements that include recent availability of the powerful technique of high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (CLHP-ESI-MS/MS) [16-18]. [Pg.13]


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See also in sourсe #XX -- [ Pg.72 ]




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Chemical conversion

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