Organic polysulfides

T Polysulfide Organic polysulfide polymer Ozone, oils, solvents, thinners, ketones, esters, aromatic hydrocarbons Mercaptons, chlorinated hydrocarbons, nitro hydrocarbons, ethers, amines, hetercocyclics... 

Miscellaneous Curing Reactions. Other functional groups can react with the thiol terminal groups of the polysulfides to cross-link the polymer chains and build molecular weight. For example, aldehydes can form thioacetals and water. Organic and inorganic acids or esters can form thioesters. Active dienes such as diacrylates can add to the thiols (3). Examples of these have been mentioned in the Hterature, but none have achieved... 

Numerous organic reactions of sulfur monochloride are of practical and commercial importance. Of particular importance is the reaction of sulfur monochloride with olefins to yield various types of addition products (142). With ethylene, the severe vesicant bis(2-chloroethyl) sulfide [505-60-2] (mustard gas) forms with elemental sulfur and polysulfides (see Chemicals IN war). Propylene reacts similarly ... 

The decomposition of dithionite in aqueous solution is accelerated by thiosulfate, polysulfide, and acids. The addition of mineral acid to a dithionite solution produces first a red color which turns yellow on standing subsequentiy, sulfur precipitates and evolution of sulfur dioxide takes place (346). Sodium dithionite is stabilized by sodium polyphosphate, sodium carbonate, and sodium salts of organic acids (347). 

The process of sulfurization is usually carried out by a sulfur bake, in which the dry organic starting material is heated with sulfur between 160 and 320°C a polysulfide bake, which includes sodium sulfide a polysulfide melt, in which aqueous sodium polysulfide and the organic starting material are heated under reflux or under pressure in a closed vessel or a solvent melt, in which butanol, CeUosolve, or dioxitol are used alone or together with water. 

Sodium thiosulfate is a by-product of the manufacture of Sulfur Black and other sulfur dyes (qv), where organic nitro compounds are treated with a solution of sodium polysulfide to give thiosulfate. The dyes ate insoluble and ate recovered by fUtration. The fUtrate is treated with activated carbon and filteted to obtain a sodium thiosulfate solution. After concentration and crystallization, the final product assays ca 96% Na2S202 5H20 (34) (see Dyes AND... 

The second catalyst paste of the two-paste product is a curing agent. A wide variety of materials convert the Hquid polysulfide polymers to elastomeric products. Alkalies, sulfur, metallic oxides, metallic peroxides, organic peroxides, and many metal—organic salts, ie, paint driers, are all potential curing agents. 

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. 

Poly sulfide Polymers. These polymers are made up of aliphatic hydrocarbon units connected by di-, tri- or tetrasulfide links. The synthetic rubber found useful in ordn has hydrocarbon units linked by either O or formal segments. The polymers are usually prepd by the condensation of a suitable organic dihalide, usually the chloride, with aq Na polysulfide. According to Ref 8, the most practical organic dichloride is dichlorodiethylformal viz, Bis[ 2[Pg.827]

Very often inorganic polysulfides have been used to synthesize organic polysulfanes by reaction with, for example, alkyl or aryl halides [109, 110], e.g. ... 

The various oxidation states of sulfur have been determined by polarography. The electrochemical oxidation of sulfide ions in aqueous solution may lead to the production of elementary sulfur, polysulfides, sulfate, dithionate, and thiosulfate, depending on the experimental conditions. Disulfides, sulfoxides, and sulfones are typical polarographically active organic compounds. It is also found that thiols (mer-captans), thioureas, and thiobarbiturates facilitate oxidation of Hg resulting thus in anodic waves. 

Oxidation may be achieved in the presence of oxygen or air. Other suitable oxidants include sulfur, sodium polysulfide, iron (III) chloride, potassium ferro-cyanide (III) or potassium dichromate, peroxydisulfate or salts of aromatic nitro-sulfonic acids. An aqueous/alkaline medium is used in the presence of a high boiling organic solvent which is not miscible with water or which is almost immiscible with water. Cyclization with chlorosulfonic acid can be followed directly by oxidation with bromine to afford the thioindigo system, without separation of the intermediate. 

The necessary conditions are sources of iron oxide, dissolved 804 and organic matter, and sufficiently reducing conditions for reduction of 804 coupled to intermittent or localized oxidizing conditions to produce elemental 8 or polysulfide. Potential acidity develops by the removal of alkalinity (represented by HC03 in Equation 7.2) from the sediment by diffusion and tidal action. What... 

S " ") and depolymerization (S " " - Sg + Sy -t- Sg 4-. ..). This free radical mechanism has often been discussed on the basis of the observed first order rate equations found for the formation of it-sulfur and the decomposition of organic polysulfides as well as on the basis of the experimentally determined apparent activation energies (50-150 kJ/mol ). However, this type of mechanism seems rather unlikely at least at moderate temperatures sinc (a) no free radicals have been detected in liquid sulfur below 170 (b) only the... 

The mechanisms (a)-(c) can also be discussed in connection with the thermal decomposition and rearrangement reactions of organic polysulfides. For example, dimethyl tetrasulfide when heated to 80 °G for several hours disproportionates to the corresponding tri-, penta- and hexasulfides. On prolonged heating small amounts of disulfide are formed in addition... 

The electroreduction of sulfur in nonaqueous solvents (DMF, DM SO etc.) has been studied by several authors for the past 35 years [47-60]. Experimentally, a solution of sulfur is yellow (pale) and the reduced solutions are intensely colored. Electrochemically, the response of the electroreduction of sulfur in classical organic solvent (DMF, DMA, DMSO, CH3CN etc.) is similar. The reduced forms, that is, polysulfides S or S , have characteristic absorption bands in the visible range. Structurally, sulfur is a ring and polysul-fldes are expected to be Knear chains. To understand the electrochemical behavior of sulfur, it was necessary to take into account these structural aspects. This was done only in 1997 [60]. 

Therefore, a complete description of the redox properties of sulfur and polysulfides in classical organic solvents has been obtained on the following basis only 8g and the radical anions 8 are reducible and only the dianions 8 and 8g are oxidable. The electrochemical process has been validated in DMF by comparing simulations and the experimental data in a wide range of temperatures (233 to 313 K) and scan rates (0.005 to 2.0 Vs ). It can be reasonably extended to other organic solvents. Thermodynamic and kinetic parameters have been discussed in Ref. 60. It must be noted that Paris et al. [58] describe the reduction of sulfur... 

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