Scavengers dimethyl sulfide

CF3CO2H, PhSCH3, 25°, 3 h. ° The use of dimethyl sulfide or anisole as a cation scavenger was not as effective because of side reactions. Benzyl ethers of serine and threonine were slowly cleaved (30% in 3 h complete cleavage in 30 h). The use of pentamethylbenzene had been shown to increase the rate of deprotection of 0-Bn-tyrosine. ... 

CF3COOH, PhSH, 20°, 1 h, 100% yield.18 Thiophenol is used to scavenge the liberated r-butyl cations, thus preventing alkylation of methionine or tryptophan. Other scavengers such as anisole, thioanisole, thiocresol, cre-sol, and dimethyl sulfide have also been used.19... 

Table 8-6 presents an overview on the concentrations of the major ions in rainwater observed at various locations. Table 8-7 provides some information on cloud and fog waters. In maritime regions seasalt is an important source of cloud condensation nuclei, and it undergoes effective below-cloud scavenging as well. Sodium chloride accordingly contributes the largest fraction of all ions in rainwater. Some of the other ions usually are somewhat enriched in comparison with their relative abundances in seasalt. The enrichment of potassium and calcium is due to the admixture of aerosol from continental sources, and that of sulfate arises from the oxidation of gaseous precursors such as dimethyl sulfide of S02- This excess sulfate is associated almost exclusively with submicrometer-sized particles (see Section 7.5.1). 

Scavengers are usually added to arrest the p-methoxybenzyl carbocation before it can do any collateral damage. Typical combinations of Lewis acid and scavenger are trifluoroborane and triethylsilane tin(IV) chloride and benzene-thiol - catalytic amounts of tin(II) chloride dihydrate and ethanelhiol - catalytic amounts of trichloroalane and ethanethiol magnesium bromide etherate and dimethyl sulfide and trichloroborane and dimethyl sulfide [Scheme 4.188]. Cerium(III) chloride heptahydrate together with sodium iodide cleaves p-methoxybenzyl ethers in refluxing acetonitrile- as does iodine in refluxing methanol but in the latter case, isopropylidene acetals do not survive. ... 

Scavenger, a compound to trap reactive intermediates. When cleaving protecting groups of the tert.-butyl or benzyl type, scavengers such as anisole, thioanisole, dimethyl sulfide, or triisopropylsilane must be added to the reaction mixture in order to avoid side reactions of the intermediate carbenium ions. 

A significant advantage in using toluene or ethanol in storage solutions is their dual role as solvents and stabilizers. Other effective radical scavengers, such as dimethyl sulfide, 2-mercaptoethanol, and benzyl alcohol, are occasionally used as stabilizing additives to solutions of labeled compounds in various solvents, but usually only in cases where they are compatible with the intended studies as they are difficult to separate from the labeled solute. 

Most of the separation procedures are based on the precipitation [27, 68, 72, 76, 80, 89, 99, 110, 139, 158, 170] or extraction [11, 72, 81, 119, 122, 124, 139, 162] of the Pd dimethyl-glyoxime (DMG) complex. In combination with the commonly used scavenger precipitations of Fe, La, or Zr hydroxides and Ag halides quite high decontamination factors can be achieved (see for example procedure 1 below). The samples for counting are prepared using either Pd metal or insoluble Pd compounds, like DMG complex, sulfide, or iodide. 

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