Polysulfide reactivity

Sodium bisulfide Sodium polynaphthalene sulfonate Sodium polysulfide Urea-formaldehyde resin polysulfides, reactive (Chloropropyl) methylsiloxane-dimethylsiloxane copolymer polysulfone mfg. 

The dinuclear ion Mo2(S2) g (F - prepared from the reaction of molybdate and polysulfide solution (13) is a usehil starting material for the preparation of dinuclear sulfur complexes. These disulfide ligands are reactive toward replacement or reduction to give complexes containing the Mo2S " 4 core (Fig. 3f). 

Diisocyanates or Polyisocyanates. The thiol end groups of the hquid polysulfides are quite reactive with isocyanates (eq. 3). Typical chisocyanates, such as 1,3-toluene chisocyanate (m-TDl) and diphenylmethane-4,4 -diisocyanate (MDl), ate effective in curing hquid polysulfides. Using hquid polysulfides in-... 

In the presence of the organic siHcate, the heavy-metal salts trigger the chain extension and cross-linking reactions that lead to siHcone mbber and volatile ethanol as a byproduct. Useful metal soaps iaclude stannous octanoate [1912-83-0], ziac octanoate [557-09-5], dibutyltin dilaurate [77-58-7], and dibutyltin diacetate [1067-33-0]. The reactivity of the different salts varies considerably. Stannous octanoate effects a cure ia 0.5—2 min ziac octanoate may require 24—96 h the dibutyltin dilaurate, 10—20 min. Heat and moisture accelerate the curing rate, but to a lesser degree than ia the case of the polysulfide mbbers. 

The initial sulfur copolymer that is formed is often high conversion and gelled. Molecular weight is reduced to the required level by cleaving some of the polysulfide Linkages, usually with tetraethylthiuram disulfide. An alkaU metal or ammonium salt (30) of the dithiocarbamate, an alkaU metal salt of mercaptobensothiasole (31), and a secondary amine (32) have all been used as catalysts. The peptization reaction results in reactive chain ends. Polymer peptized with diphenyl tetrasulfide was reported to have improved viscosity stabiUty (33). 

Abstract Inorganic polysulfide anions and the related radical anions S play an important role in the redox reactions of elemental sulfur and therefore also in the geobio chemical sulfur cycle. This chapter describes the preparation of the solid polysulfides with up to eight sulfur atoms and univalent cations, as well as their solid state structures, vibrational spectra and their behavior in aqueous and non-aqueous solutions. In addition, the highly colored and reactive radical anions S with n = 2, 3, and 6 are discussed, some of which exist in equilibrium with the corresponding diamagnetic dianions. 

The polysulfidic moieties of the silanes are unstable, and cleavage of the sulfur groups results in active sulfur species. A notorious problem with this kind of coupling agents is the balance between its reactivity towards the silica, requiring a temperature of at least 130°C to obtain an acceptable speed, and its eagerness to react with the rubber polymer, which starts to become noticeable at temperamres above 145°C. Furthermore, the primary and secondary reactions are chemical... 

Metal sulfides and polysulfides have been extensively studied because of their key role in important catalytic processes such as the hydrodesulfurization of crude oil or the biosynthesis of metalloproteins. The coordination chemistry of polysulfides85 86 has been comprehensively reviewed similar to that of the heavier polychalcogenides.10,12 15 Polysullido complexes are themselves reactive and their exothermic desulfurization can be exploited as a means of... 

Polysulfide polymers Polysulfide polymers increase the reactivity of some explosives and propellants. They are not compatible with PETN, Pentolite, Composition B, Amatol or Tetryltol. Polysulfide rubbers absorb some NG from DB and triple-base ( ) propellants. However, some propellants show little or no reactivity in the presence of polysulfides. 

Molybdenum complexes of polysulfide ligands are reactive and, for example, readily make and break sulfur-carbon bonds, a property undoubtedly relevant to the involvement of Mo—S... 

Reactions of the Disulfide Group. Besides the thiol end groups, the disulfide bonds also have a marked influence on both the chemical and physical properties of the polysulfide polymers. One of the key reactions of disulfides is nucleophilic attack on sulfur (eq. 4). The order of reactivity for various thiophiles has been reported as (C2HsO)3P > R , HS-, C2H5S > C6H5S > C6H5P,... 

The dissolution rate of goethite by sulfide was found to increase with surface area and proton concentration. Pyzik and Sommer (21) suggested that HS" is the reactive species that reduces surface ferric iron after exchanging versus OH . A subsequent protonation of surface ferrous hydroxide would lead to dissolution of a surface layer. Elemental sulfur was the prominent oxidation product polysulfides and thiosulfate were found to a lower extent. The dissolution rate R (in moles per square meter per second) of hematite by sulfide was demonstrated to be proportional to the surface concentration of the surface complexes >FeHS and >FeS (22). 

Barium sulfide. [CAS 21109-95-5]. BaS. grayish-white solid, fonned by heating barinm sulfate and carbon, reactive with II20 to fonn barium hydrosulfide, Ba(SH)2, solution. The latter is also made by saturation of barium hydroxide solution with H S. Banum polysulfides are formed by boiling barium hydrosulfide witli sulfur. 

Strontium sulfide. SrS. [CAS 1314-96-1], grayish-white solid (thermodynamic Ksp 500) reactive with water to form strontinm hydrosulfide, Sr(SH)2, solution. Strontium hydrosulfide is formed (1) by reaction of strontium sulfide and H2O, (2) by saturation of strontium hydroxide solution with H2S, Strontium polysulfides are fonued by boiling strontium hydrosulfide with sulfur,... 

The addition of aromatic thiols, ArS-, to cyanamide, NCNH2, is general acid catalysed, giving isothiourea as product.311 A significant movement of a hydron in the TS to the cyano nitrogen atom is indicated. The reactivity of sulfur towards thio-carboxylate ions (341 R = Ph, Me, Bu ) has been looked at and among the species formed are Sj/Sf polysulfide ions (342) and (343).312... 

The results obtained for reaction of acrylic acid (200 /iM) with tetrasulfide (1.25 mM 5 mM) as well as bisulfide (5 mM) are shown in Figurel. In the reaction with HS, the concentration of 3-MPA did not noticeably increase after treatment with TBP. If polysulfide ion was the actual reactive species in this reaction, then TBP treatment should have caused a significant increase of 3-MPA, in comparison to that without TBP. Therefore, these results indicate that HS was the reactive species in the sulfide medium. However, in the reaction of acrylate with the polysulfide ion, S42, determination of 3-MPA concentration after TBP treatment revealed a large increase, indicating that S42 reacted with acrylate to produce 3-tetrasulfidopropionic acid. The reactivity of tetrasulfide with acrylate was much higher than that of bisulfide. Similar results were also obtained for reaction of acrylonitrile with HS and S42 (Figure 2). The kinetic data are summarized in Table I. In the polysulfide senes low concentrations of 3-MPA were also observed without TBP treatment. It is possible that this 3-MPA was formed from uncatalyzed dissociation of the polysulfide addition product... 

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