Polysulfides preparative methods

An interesting combination of methods is the polysulfide flux method, which can be usedforthe preparation of Ln202S (Ln trivalent rare-earth ion)-based luminescent materials (e.g. Y202S Eu or Gd202S Pr) [5.228]. In this method, the mixed oxides of the metals are mixed with excess sulfur and an alkali metal carbonate. On heating, the alkaline carbonate decomposes and reacts with sulfur to form a Uquid polysulfide flux. The oxides react with the polysulfide flux to form the oxysulfide. Flux residues can be removed by washing the reaction product in water. 

Although it is relatively easy to prepare high-molecular-weight polysulfides, these products have not yet found applications. This is mostly due to a lack of industrially applicable monomer preparation methods. Neither ethylene sulfide nor propylene sulfide can be prepared by direct reaction of the corresponding olefins with elemental sulfur. Moreover, it is difficult to obtain polyethylene sulfide) sufficiently stable at higher temperatures and its odour may become offensive. 

These make up the largest class and display a wide variety of terminal groups, from simple and substituted alkyls and aryls to acyls and amino acid residues. Disulfides are usually quite stable polysulfides are less stable but can, like the disulfides, be obtained in a variety of ways. Schoberl and Wagner (198) have recently reviewed preparative methods for tri-, tetra-, and pentasulfides. Only a few hexasulfides are known for example, dimethyl, diethyl, and dibenzyl hexasulfides which were prepared by Bohme and Zinner (84) from the alkyl hydrogen trisulfides by oxidation with iodine they are yellow oils at room temperature. The bis(thiocarbamyl)-hexasulfides studied by Levi (164) and Blake (28) are crystalline and apparently stable. 

Hydrocarbon Gngnard reagents give the alkyl cyanides, whereas perfluo-rinated Grignard reagents produce the sulfides This reaction is useful for the preparation of alkyl perfluoroalkyl sulfides to the exclusion of di and polysulfides, which are produced by other methods... 

Electrochemical preparation studies on low-dimensional structures of ternary or higher order compounds have appeared in the last few years. For example, whiskers of the quasi-ID copper(I) sulfide series KCuv-jcSa (0 < x < 0.34) were grown by employing electrochemical methods via anodic dissolution of copper electrodes, at 110 C in ethylenediamine solution of polysulfide K2Sn (n = 5, 6) electrolytes and, in some cases, CuCl [165]. 

The chemistry of diorgano polysulfides has been extensively investigated for decades and a variety of methods has been described for their preparation 1 22 24 However, only three major methods have been applied to the synthesis of polysulfides in cystine peptides thus far. 

The most significant improvement came in the early 1940s when a method for preparing thiol-terminated liquid polysulfides was developed. Cure of the liquid polysulfides could be accomplished by oxidative coupling. Thus, in effect, a mbber could be compounded without the need of heavy mixing equipment. One of the first large-scale applications of the liquid polysulfides was as a binder for solid rocket fuel. From about 1946 until 1958, these binders were used in various rocket systems and the aliphatic polysulfides achieved commercial success. The switch to predominately liquid-fueled rockets in 1958 ended this phase of the polysulfide business. 

Diethyl mercaptoacetal has been prepared by treating diethyl bromoacetal with potassium hydrosulfide 3 by the reduction of 1,1,11 -tetraethoxyethyl disulfide 3 with lithium aluminum hydride by reduction of 1,1-diethoxyethyl benzyl sulfide,3 41,1,1/,1/-tetraethoxyethyl disulfide,3 and 1,1,1, 1 -tetracthoxyethyl polysulfide 3 with sodium and liquid ammonia. The method described is adapted from the last-named preparation. Dimethyl mercaptoacetal has been prepared by the same methods.3... 

Sulfur dyes are a special class of dyes with regard to both preparation and application, and knowledge of their chemical constitution [1], They are made by heating aromatic or heterocyclic compounds with sulfur or species that release sulfur. Sulfur dyes are classified by method of preparation as sulfur bake, polysulfide bake, and polysulfide melt dyes. Sulfur dyes are not well-defined chemical compounds but mixtures of structurally similar compounds, most of which contain various amounts of both heterocyclic and thiophenolic sulfur. 

The polarographic and potentiometric methods are not HPLC-run. The polarographic method relies upon the measurement of half-wave potentials of various sulfur compounds reacting with a mercury electrode. It is sensitive to submicromolar concentrations (Luther, pers. com.). While sulfide, thiosulfate, polysulfide and polythionates can be measured, the initial sample must be subdivided and pretreated in different ways. The disadvantages are that sample preparation ana analysis are time-consuming and there is no way to preserve samples for later analysis nor to study organic thiols with precision., ... 

Arretz, E., Lopez, F. Method for preparing organic disulfides and polysulfides from mercaptans and sulfur in the presence of heterogeneous styrene-divinylbenzene copolymer catalysts having pendant guanidine or amidine groups. 1996, WO 9721673. 

Method 1 Preparation of sodium polysulfides from sulfur and lye... 

This method of preparing sodium polysulfides can be used to purify sulfur to high degree. When hydrochloric acid is added to the mixture, pure sulfur precipitates. 

Of the stabilization methods, the polysulfide pulping process is of practical importance. The influence of polysulfides is based on a specific oxidation of the end groups to carboxyl groups via glucosone intermediates (cf. Section 8.1.3). Polysulfides can be prepared by catalytic oxidation of sulfide in the white liquor or by adding elemental sulfur into the kraft cooking liquor ... 

Interesting ternary chalcogenides have been prepared employing electrochemical methods via anodic dissolution of copper or silver electrodes at low temperatures. For example, the series of KCu - S4 (0 < x < 0.34) was prepared in an ethylenediamine solution of polysulfide K2S (x = 5, 6) electrolytes. Single crystal stmcture analysis confirmed the once ambiguous space group of these compounds and showed that the KCU7S4 phase which exhibits an unusual insulator-to-metal transition is non-stoichiometric. The stmcture... 

Aminobenzaldehyde has been prepared by the action of sodium polysulfide upon. f>-nitrotoluene,3 4 on which the method described is based. 

Polysulfide ions [8 ] are not prepared by deprotonation of the corresponding polysulfanes. Instead, methods of synthesis include reactions 15.18 and 15.41, and that of H2S with S suspended in NH4OH solution which yields a mixture of [NH4]2[S4] and [NH4]2[S5]. 

In contrast to polysulfides, cationic polymerization is the only method to prepare high-molecular-weight polyamines. Polyethyleneimine is the only polymer commercialized among the group of cationically prepared polysulfides and polyamines. Branched polyethyleneimines, are used on the technical scale mostly as flocculants. 

Polysulfide rubber manufacturing processes are described in more detail by Bertozzi [26]. Briefly, the processes involve preparation of sodium polysulfide (S + NaOH), and reaction with bis(2-chloroethyl)formal along with 2% of a branching agent such as 1,2,3-trichloropropane to give a mercaptan terminated polymer of MW approximately 80,000 similar to that described in Preparation 2-2, Method A. 

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