A-Containing compounds

This chapter reports about an investigation on the catalytic gas-phase armnoxidation of u-hexane aimed at the production of 1,6-Ce dinitriles, precursors for the synthesis of hexamethylenediamine. Catalysts tested were those also active and selective in the ammoxidation of propane to aciylonitrile mtile-type V/Sb and SnA /Nb/Sb mixed oxides. Several A-containing compounds formed however, the selectivity to cyano-containing aliphatic linear Ce compounds was low, due to the relevant contribution of side reactions such as combustion, cracking and formation of heavy compounds. 

The catalyst composition has a role in the control of selectivity. The rutile-type V/Sb/(Nb) mixed oxide activates the hydrocarbon and ammonia. However, most of the ammonia is burnt to N2, rather than being inserted on the hydrocarbons this likely occurs because the catalyst is not veiy efficient in the generation of the selective Me=NH species when reaction temperatures lower than 400°C are used (11). In fact, with all catalysts the selectivity to A -containing compounds increased when the reaction temperature was increased, and the selectivity to N2 correspondingly decreased (Figure 40.6). The dilution of the active phase with tin... 

Measurements based on the law of conservation of energy are of two main types. In phase change calorimetry the enthalpy of the reaction is exactly balanced by the enthalpy of a phase change of a contained compound surrounded by a larger reservoir of the same compound used to maintain isothermal conditions in the calorimeter. The latter enthalpy, the measurand, is often displayed indirectly through the change in the volumetric properties of the heat reservoir compound, e.g. ice/water. 

Oxime ethers from (R)- or (.V)-0-( 1 -phenylhydroxylamine) in asymmetric syntheses of A-containing compounds, in particular, of piperidine alkaloids, lactams, five-to eight-membered A-heterocycles 04CC1341. 

A number of papers contribute to an understanding of the mechanistic features of the photo-oxidation of A -containing compounds. A labelled guanosine... 

It is possible that adsorption of A/-containing compounds reduces the electrophilic character of the catalyst (by removing traces of acids or poisoning metal ions). For this reason hydrogenolysis occurs via an 8 2-like mechanism instead of the faster S l. Additional evidence is that oxidic or unreduced catalysts give the best selectivity in debenzylation [9]. It has also been found that for O-benzyl systems palladium oxide was much more effective than palladium metal whereas no such effect was observed with /V-benzyl systems [66]. 

Tobacco chemists have shown considerable interest in the chemistry and biochemistry of the diverse set of A-containing compounds in tobacco and tobacco smoke. Numerous studies on the presence of nitrogenous compounds in tobacco and tobacco smoke have been published. These studies have reported on various aspects of the origins of nitrogenous... 

NO, in tobacco smoke has been quantified by calorimetric analyses (189, 3441, 3720), such as the Saltzman method (19A07), and by the chemical emission method (2122), which has been shown to be a rapid method for quantification (1884). Most of the NO, present in fresh MSS is NO, only a small amount of NO2 is present (189, 816, 2803). The concentration of NO2 in MSS increases (189, 2803, 3691) with the age of the smoke, and can reach levels of 200 ppm after 60 seconds (189). NO2 formation is believed to result from the auto-oxidation of NO. It has also been suggested that some of the NO2 produced by oxidation is converted (2941, 4058) to methyl nitrite through a reaction with methanol in the smoke (1884). Predominate precursors of NO are nitrates (189) and other A-containing compounds in the tobacco. N2O (2941) and HNO3 (4058) have also been reported as components of MSS in addition to the above compounds (1884). The currently preferred method for the determination of NO, is chemiluminescence (1930,19A02). 

Ishiguro, S. and S. Sugawara Comparisons of volatile A-containing compounds in the smokes of lamina and midrib of flue-cured leaves Agr. Biol. Chem. 41 (1977) 377-382. 

Ishiguro, S., Y. Watanabe, and T. Okada Formation of volatile nitrosamines in sidestream smoke from cellulose cigarettes impregnated with various A-containing compounds 38th Tobacco Chemists Research Conference, Program Booklet and Abstracts, Vol. 38, Paper No. 37, 1984, p. 20. 

Table 10. Antiviral Marine-Derived Peptides, Alkaloids, Proteins, Nucleosides and Other A -Containing Compounds...

Many marine-derived peptides, alkaloids, proteins, nucleosides and other A -containing compounds were shown to be active against several viral species. Table 10 illustrates these activities. 

Supramolecular isomerism in rotaxanes, catenanes, and "container" compounds. A. Moving along a rotaxane axle can lead to isomerism if there are two different "docking stations". B. Similarly, catenanes can exist in isomeric forms if there is structural diversity in one of the rings. C. A conceptualization of isomerism in a container compound. 

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