Polysulfide reactions

Under these circumstances, it seems reasonable to look for alternative explanations for the polysulfide reactions and in this connection it is interesting to note that a bimolecular mechanism is in better agreement with the data reported for the trisulfide disproportionation discussed above. This reaction has been followed by H n.m.r. spectroscopy at different temperatures and initial concentrations. Equimolar amounts of diethyl and di-n-propyl trisulfide were used and after the equilibrium had been established the equilibrium constant... 

Sulfur Modified with Dicyclopentadiene. The beneficial use of dicyclopentadiene to modify sulfur has been reported by a number of workers including Currell et al. (3), Sullivan et al. (4), and also Diehl (5). Currell et al. showed that the interaction of dicyclopentadiene and elemental sulfur at 140 °C gives a mixture of polysulfides and free elemental sulfur which, even after standing for 18 mo, is held as a mixture of presumably monoclinic and noncrystalline sulfur. Sullivan et al. reported that the minimum concentration of dicyclopentadiene required to stop permanently the embrittlement of elemental sulfur is 13% if the reaction temperature is less than 140°C and only 6% if the reaction temperature is greater than 140 °C. Presumably the polysulfide reaction products form a solid solution with the unreacted sulfur from which orthorhombic sulfur cannot crystallize. 

The polymer is then in a stripped state in which no polysulfane group exceeds the disulfane stage. Thiokol FA is a copolymer of dichloroethane and the bis(2-chloroethyl)formal sodium polysulfide reaction product. 

The kinetics of the polysulfide reactions are also little known (a recent review is available ) and difficult to study. At the operating temperature the exchange currents are so high that they have not been reliably determined. The absence of a supporting electrolyte further complicates the interpretation of transient voltammetry. 

Toluene diisocyanate polysulfide reaction products [153]. Phenol-formaldehyde polysulfide condensation polymers [154]. 

These processes of isotope evolution explain the wide diversity of both 5 8 values for the organic-8 and the pyrite, as well as the fact that the pyritic " 8 values are the most " 8 depleted. Because of the complexity of the various mechanisms controlling the formation of iron sulfide — pyrite (see review by Goldhaber (2004)) and the slower reaction of the polysulfide reaction with the 80M, the difference of " 8 values for pyrite compared to the organic-S varies. Those variations A6 " 8poiysuifides pyrite will later control the A5 " 8organic-pyrite-... 

LaLonde R. T., Ferrara L. M. and Hayes M. P. (1987) Low-temperature, polysulfide reactions of conjugated ene carbonyls a reaction model for the geologic origin of S-heterocycles. Org. Geochem. 11, 563-571. 

Fettes and Gannon were the first to report reactions of liquid polysulfide polymers with epoxy resins [16]. In these adhesives, the epoxy resin is the major component. The polymer LP-3 in which n = 8 has been used most extensively. This polymer has a moleeular weight of about 1000 with viscosity in the range 7 to 12 P. The epoxy resins most widely used in adhesive formulations have viscosities the range 80 to 200 P with an epoxy equivalent of 175 to 210. Typical resins are Epon 820 and 828 (Shell), ERL-3794 (Union Carbide), and Araldite 6020 (CIBA). The epoxy-polysulfide reaction is prompted by organic amines (e.g. diethylenetriamine and benzyldimethylamine). The general reaction of a polysulfide polymer, epoxy resin, and amine hardner is... 

The foregoing relationships of chain length to extent of reaction would then be expected to apply to such step polymerizations as are involved in the synthesis of poly(alkylene sulfides) from a dihalide and sodium polysulfide (polycondensation) or in the formation of the urethane polymers from glycols and diisocyanates (polyaddition). The polysulfide reaction is actually carried out in a suspension of the dihalide in an aqueous solution of the polysulfide, using a surfactant to stabilize the resulting polymer suspension. 

For example, 1,4-dichlorobutane reacts with sodium tetrasulfide to produce the corresponding aliphatic polysulfide (reaction 3)... 

The reaction of sodium metal with sulfur in their molten form also affords sodium polysulfide (reaction 8) [6]... 

Polysulfides were also produced by chemical reaction of deposited sulfur with sulfur(—II) species in solution, providing a method of de-passivating anodes on which elemental sulfur is formed unintentionally. The kinetics of the coupled chemistry-electrochemistry of polysulfide reactions has been modelled and studied experimentally [10-12]. 

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