Oximes stabilized

Barnard, K. R. Turner, N.L. and Shiers, D.W. (2010) LIX 63 stability in the presence of Versatic 10 imder proposed commercial extract and strip conditions, part III Effect of manganese and cobalt loading on oxime stability at 30°C Hydrometallurgy 104 268-277... 

The copper-chelating abihty of sahcylaldoxime has been used to remove copper from brine in a seawater desalination plant effluent. A carbon—sorbate bed produced by sorption of the oxime on carbon proved to be extremely effective in the continuous process (99). In another apphcation, the chelating abihty of sahcylaldoxime with iron and copper was used to stabilize bleaching powders containing inorganic peroxide salts (100). 

Scheme 5 details the synthesis of / -cormorsterone (14) from 17. Oxidative scission of both carbon-carbon double bonds in 17 with ozone, followed by two straightforward operations, furnishes intermediate 38. The stability of the oxime in these systems is noteworthy, and is attributed to its hindered nature. At this juncture, it is instructive to note that substituted cyclopentene rings, like the... 

Hantzsch was unable to provide any direct experimental proof for his hypothesis. His grounds for assigning configurations were the analogies to oximes, such as the differences in stability already mentioned. 

Several functional groups containing carbon-nitrogen double bonds can participate in radical cyclizations. Among these are oxime ethers, imines, and hydrazones.337 Hydrazones and oximes are somewhat more reactive than imines, evidently because the adjacent substituents can stabilize the radical center at nitrogen.338 Cyclization at these functional groups leads to amino- substituted products. 

Oximes have been used as protecting groups for carbonyl compounds owing to their hydrolytic stability. Consequently, the development of newer deoximation reagents... 

The transformation of oximes to lactams (the Beckmann rearrangement) was one of the earliest such acid-catalyzed reactions to be reported with TS-1 (138) and TS-2 (247) catalysts. The rearrangement of cyclohexanone oxime to e-caprolactam proceeds with high selectivity in the presence of TS-1, with high catalyst stability (138,247). 

Oximes generally demonstrate good stability in the solid state when stored at low temperature. Simple oximes show reasonable stability in neutral aqueous solution but hydrolyze to hydroxylamine and the parent ketone under acidic or basic catalysis [2], As noted, nitro-containing oximes, such as FK409 (9), spontaneously decompose... 

Thermochemically is the operative word here. After all, NO can formally delocalize and thus stabilize both negative and positive charges as illustrated by the acidity of oximes cf. the well-established existence of (R2CNO) and the Nef reaction, cf. the putative existence of (R2CNO)+. 

Dining preparation of tris(ketoximino)silanes, two violent explosions attributed to acid-catalysed exothermic rearrangement/decomposition reactions occurred. Although these silane derivatives can be distilled under reduced pressure, the presence of acidic impurities (e.g. 2-butanone oxime hydrochloride, produced during silane preparation) drastically reduces thermal stability. Iron(III) chloride at 500 ppm caused degradation to occur at 150°, and at 2% concentration violent decomposition set in at 50°C. 

Furthermore, by in vitro experiments, it has been verified that stereospecific activation of alprenoxime is organ-specific, occurring in the eye and not systemically. When administered locally to rabbits, marked decreases in intra-ocular pressure were observed, whereas oral administration elicited almost no cardiac effects. Such ketoximes represent promising chemical delivery systems in the treatment of glaucoma However, a major limitation is their poor stability in solution, seemingly due to hydrolysis of the oxime function. 

An oximine (i.e., a substituted oxime) analogue of alprenoxime was examined in an attempt to overcome the problem of low stability in aqueous solution. To this end, the methoxime analogue of alprenolol (11.74, R = Me) was prepared and evaluated [109]. Stability in solution was greatly improved at neutral pH. Topical administration to rabbits produced a decrease in intraocular pressure that had the same onset and intensity as that produced by alprenolol, but that lasted longer. Alprenolol was, indeed, formed in eye tissues as a metabolite, with the peak concentration reached 30 min after topical administration of the methoxime. 

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