Stability of sulfur

Like NO, the stability of H2S and HS under physiological conditions is influenced by a number of inorganic and organic components that catalyze oxidation reactions. 

---

Table 2. Stability of Sulfur Hexafluoride in Various Materials of Construction ...

Martin D. Neuworth The author did not make any distinction between sulfur in completely aromatic rings and sulfur in hydroaromatic or nonaromatic ring structures. Since the stability of sulfur in completely aromatic structure is higher than in other configurations, the dyes might be separated on this basis independently of available hydrogen or volatile matter. 

The structure of 881 was proved by x-ray diffraction [193]. The possibility of carrying out these syntheses may be explained as due to the sufficently high stability of sulfur-and selenium-containing azomethines within a heterocyclic series, in comparison with their aromatic analogues (compare the data of Sec. 3.5.2.1), which is related to the existence of 471 as the aminomethylene form b [15,194-197]. 

The great kinetic stability of sulfur hexafluoride 73>74>, like that of carbon tetrafluoride 73>, particularly toward nucleophilic reagents, may be viewed as arising from the presence about the central atom s kernel (and about the kernels of the fluorine atoms) of a nearly complete, protective sheath of electrons with no pockets 52> of sufficient depth (orbitals of sufficiently low energy) to permit effective coordination with the unshared electrons of an entering nucleophile. The possibility remains, however, of attack by electrophilic reagents, e.g., by strong Lewis acids, such as sulfur trioxide 74>. 

Stability of Sulfur-Infiltrated Concrete in Various Environments... 

Ginosar, D.M., Glenn, A.W., and Petkovic, L.M., Stability of Sulfuric Acid Decomposition Catalysts for Thermochemical Water Splitting Cycles, paper presented at the AlChE Spring Meeting 2005, Atlanta, 2005. 

The comparative study on the molecular structure and relative stability of sulfur-containing heteropropellane compounds 9 with other heteroatoms such as NH and O were investigated by ab initio method <2000JCM93>. 

In order to look more closely at the conditions under which sulfur radical cations in Met can be stabilized by lone pairs of electrons from neighboring sulfur atoms, two other cyclic model dipeptides, c-(D-Met-L-Met) and c-(Gly-L-Met), were studied with combined optical and conductometric detection following radiolytic oxidation. Little or no intramolecular stabilization by the unoxidized sulfur in the neighboring Met was observed in c-(D-Met-L-Met) (Fig. 1, right) in contrast to the previously observed intramolecular sulfur stabilization of the sulfur radical cation in the isomer c-(L-Met-L-Met) (Fig. 1, left). This oxidation pattern observed in c-(D-Met-L-Met) was confirmed using the oxidation of c-(Gly-L-Met) which has no chance for intramolecular stabilization of sulfur radical cation. 

The order of increasing thermal stability of sulfur compounds is sulfides, disulfides, mercaptans, and thiophenes, which is consistent with the fact that mercaptans predominate in petroleum products that have been thermally treated and that increasing concentrations of thiophenes are found as the thermal conditions become more severe (117). This same order may be observed, for three of the sulfur compound types, in the average bond energy data presented by Remick (130) ... 

In this work, zirconium acetate solution was used in order to increase the pH of the pillaring solution and the content of sulfate ions introduced. Different preparation parameters and their effect on the structural and textural properties have been investigated. The resulting materials present a best zirconium-sulfate intercalation with higher sulfate rate and develop very high thermal stability of sulfur even at about 830 °C. 

The chemistry of )9-(thiocarbonyloxy)alkyl radicals stands in complete contrast to that of the (acyloxy)alkyl radicals, with elimination, while not the rule, being the norm [I]. The difference between the acyloxy and thiocarbonyloxy series is likely a consequence of the much weaker thiocarbonyl bond and the related higher stability of sulfur-centered radicals. The method has been developed in combination with the Barton deoxygenation method (Volume 1, Chapter 1.6) as a means of converting a vicinal diol, via the dixanthate, into an alkene (Scheme 33) [60-62]. Tributyltin hydride has been the reagent of choice for this reaction but it may also be conducted with the triethylsilane/benzoyl peroxide couple [63] and, doubtless, tris(trimethylsilyl)silane. 

In order to interpret the changes in 8 S during catagenesis thermal processes we have to understand the stabilization of sulfur during these increased temperature transformations. During the early diagenetic introduction of polysulfides into the organic matter, most of the... 

It appears that 4-hydroxypyrmtidine-2-lhiol does not react with CF3I under standard conditions. Similar to the reaction of 4-nitrolhiophenol noted above [57], this reaction requires more forcing conditions. Other 4-hydroxypyrimidine-2-thiols behave similarly. The irradiation of an anunonia solution of 2-mercapto-4-oxy-6-trifluoromethylyrimidine with CF3I must be conducted in a Pyrex ampoule at 30-45 °C to produce the S-trifiuoromethyl derivative (Scheme 25). Apparently, the reaction of these hydroxymercapto heterocyclic derivatives is complicated by stabilization of sulfur centred radicals. 

While the previously discussed findings demonstrate the stability of sulfur mustard in lipophilic tissues, the agent is rapidly hydrolyzed whenever situated in an aqueous compartment (X cudilik, 1987). Thiodiglycol (TDG) is the primary hydrolysis product, in which the chlorine atoms have been replaced by hydroxyl groups. Karvaly et al. (2008) used subcutaneous microdialysis to monitor TDG in rats exposed to sulfur mustard. Peak concentrations of 7.2-21.7nmol/L TDG were found, following percutaneous exposure to 2pM sulfur mustard. 

Sulfur mustard can be extracted from blood and tissue samples via liquid-liquid or solid phase extraction (SPE). The absolute recovery of sulfur mustard via liquid-liquid extraction with ethyl acetate appeared to be higher (80-90%) than with SPE [ca. 70%). Furthermore, the selectivity of SPE was no better than that of liquid-liquid extraction. The addition of sodium chloride, advocated by Maisonneuve et al. (1993) to avoid hydrolysis to hemi-mustard and thiodiglycol, did not appear to be necessary. Fully deuterated (dg) sulfur mustard appeared to be an excellent internal standard, since the recovery of sulfur mustard relative to the deuterated internal standard was 99% under all extraction conditions. No problems with respect to the stability of sulfur mustard in blood samples were encountered when the samples were extracted immediately after being drawn from the animal. 

---