Sulfur thermal behavior

In 1974, Vogel and his coworkers62) reported the first synthesis of the syn-benzene bisepisulfide 119 and its thermal behavior. The bisepisulfide 119 is thermola-bile and decomposes at 20 °C with a half-life of about 30 min to form benzene and sulfur as final products. When the reaction was carried out in the presence of 4-phenyl-1,2,4-triazoline-3,5-dione (PTD), 119 gave the product 120 which corres-... 

The unusual thermal behavior of the 1,3-ditellurolylium ions can be attributed to the more metallic characteristics of tellurium relative to sulfur and to tellurium-tellurium... 

S the thermal behavior of depends on its preparation since is a mixture of long chains and large rings and not a well defined chemical substance. This mixture is thermodynamically unstable with respect to a-Ss at 20 °C and in fact depolymerizes slowly at moderate temperatures already. DSC measurements of polymeric sulfur prepared from quenched melts as well as from sublimed sulfur show the polymer to melt at 100 °C followed immediately by the exothermic depolymerization. Stabilized commercial polymeric sulfur (Crystex) starts to melt only at 110 °C but otherwise behaves similarly (heating rate 10 K min ) [55]. 

In 1952, Gee [64] analyzed the thermal behavior of liquid sulfur. He was aware of the fact that the melt contains traces of cyclo-Ss (since he noticed that Se is present in sulfur vapor) besides Ss rings as well as diradical chains but initially he based his model solely on the following ring addition reaction ... 

Recently the first reported stable thioaldehyde was described, having the structure shown in equation 91. In comparing its photochemical behavior (using a medium-pressure mercury lamp at 5 °C) with its thermal behavior, it was found that two reactions occurred. These involved (a) a 1,3-silyl shift from carbon to sulfur forming a silylthioenol ether and (b) extrusion of sulfur yielding a trisilylalkene139. 

Stoler A. (1990) Studies on sulfur in Israeli oil shales and the thermal behavior of these catalytical desulfurization. Ph.D. thesis, Hebrew University of Jerusalem, Israel. 

Flame-retardant textiles are textiles or textile-based materials that inhibit or resist the spread of fire. Factors affecting flammability and thermal behavior of textile include fiber type, fabric construction, thermal behavior of textile polymer and its composition as well as the presence or absence of flame additives. On the other hand, flame-retardant additives can be classified by their chemical composition or by mode of action, i.e., gas phase action or by the formation of protective barrier [49, 50]. Moreover, flame-retardant functional finishes of cellulose-based textiles can be accomplished by [i] using inorganic phosphates, (ii) with organophosphorous compounds, [iii) with sulfur-derivatives or (iv) by grafting flame retardants monomers [49,50]. 

Pendent sulfur groups are the supposed precursors prior to an interchain crosslink formation. The synthesis of model pendent groups containing benzothiazolyl functions [132,133] has enabled their thermal behavior to be studied directly. Again, the experiments evidenced that the zinc complexes play an important active role in the desulfuration reaction of the pendent polysulfidic groups. 

The corrosion behavior of tantalum is weU-documented (46). Technically, the excellent corrosion resistance of the metal reflects the chemical properties of the thermal oxide always present on the surface of the metal. This very adherent oxide layer makes tantalum one of the most corrosion-resistant metals to many chemicals at temperatures below 150°C. Tantalum is not attacked by most mineral acids, including aqua regia, perchloric acid, nitric acid, and concentrated sulfuric acid below 175°C. Tantalum is inert to most organic compounds organic acids, alcohols, ketones, esters, and phenols do not attack tantalum. 

A mass spectrometric study was carried out to establish tbe structure of compoimd 69. Its mass spectrum contains tbe molecular ion peak m/z 252 (16.98%) and a base peak (100%) at m/z 210, corresponding to 2-(2-hydroxypbenyl)benzimidazole (70). A tendency towards decreasing the heterocycle size is characteristic of the mass spectrometric behavior of 1,5-benzodiazepin-2-ones [61] and consequently the mass spectra of these compounds contains intense peaks of the corresponding benzimidazoles. It is also known that the mass spectrometric fragmentation of 1,5-benzodiazepines is similar to their thermal or acid decomposition. In fact, refluxing compound 69 in concentrated sulfuric acid yields benzimidazole 70 as the main product. 

Hydrocracking, 30 48-52 behavior, thermal, 29 269 catalytic, 26 383 deethylation, 30 50 demethylation, 30 50 metallocarbene formation, 30 51-52 of f -decane, 35 332-333 primary coal liquids, 40 57 procedure, 40 66-67 product distribution, 30 49 reactions, over perovskites, 36 311 suppression by sulfur, 31 229 zeolite-supported catalysts, 39 181-188... 

Such a rearrangement was detected only in the presence of sulfuric acid, and furthermore at 100°C. it was supplanted by a homolytic breakdown. The products found in the purely thermal decomposition—methyl vinyl ketone and methyl vinyl carbinol—are in fact consistent with the behavior of alkyl hydroperoxides and are analogous to the products produced from the cyclic allylic hydroperoxide from cyclohexene (2). 

Factors which affect the oxepin-benzene oxide equilibrium positions are similarly expected to influence the thiepin-benzene episulfide distribution at equilibrium. Since however the thianorcaradiene tautomer has not to date been detected, the main evidence for this form is based upon the thermal instability and reactions of the thiepin system. Thus it is assumed that where the thianorcaradiene isomer is present, a spontaneous thermal decomposition involving extrusion of a sulfur atom will occur. Substitution at the 2,7-positions in the oxepin-arene oxide system leads to a preference for the seven-membered ring form and this effect was further enhanced by bulky substituents (e.g. Bu ). A similar effect was observed in thiepins and thus the remarkable thermal stability of (49) (2,7-r-butyl groups) and (51) (2,7-hydroxyisopropyl groups) contrasts with the behavior of thiepin (55)(2,7-isopropyl groups), which was thermally unstable even at -70 °C (78CL723). The stability of thiepin (49) results from the 2,7-steric (eclipsed) interactions which obtain in the thianorcaradiene form but which are diminished in the thiepin tautomeric form (relative to the episulfide tautomer). 

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