Alkyl polysulfides

Most macroscale experiments run with C/S sacrificial cathode were conducted at a potential of —0.9 V (vs. SCE). Obviously, transients species coming from the fragmentation of sulfur (radical ions or anions) can act as reducing species and nucleophiles. Very often, it appeared difficult to discriminate between different chemical (and electrochemical) pathways. Preliminary experiments based on the nucleophilicity of reduced products of dissolved sulfur led with poor selectivity to dipropionitrile sulfide (Tomilov [285]) and to alkyl polysulfides (Paris [286]). 

Speier JL. Dow Coming. Preparation of alkyl polysulfides. US patent 4,125,552. November 14, 1978. 

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... 

An aryl alkyl ketone 1 can be converted into an tn-arylalkane carboxylic amide 2 by employing the Willgerodt reaction The number of carbon centers is retained. The reaction is carried out by treating the ketone with an aqueous solution of ammonium polysulfide. A variant that has been developed by Kindler, and which is called the Willgerodt-Kindler reaction, uses a mixture of sulfur and a secondary amine instead of the ammonium polysulfide. 

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

Sealants obtained by curing polysulfide liquid polymers with aryl bis(nitrile oxides) possess stmctural feature of thiohydroximic acid ester. These materials exhibit poor thermal stability when heated at 60°C they soften within days and liquefy in 3 weeks. Products obtained with excess nitrile oxide degrade faster than those produced with equimolar amounts of reagents. Spectroscopic studies demonstrate that, after an initial rapid addition between nitrile oxide and thiol, a second slower reaction occurs which consumes additional nitrile oxide. Thiohydroximic acid derivatives have been shown to react with nitrile oxides at ambient temperature to form 1,2,4-oxadiazole 4-oxides and alkyl thiol. In the case of a polysulfide sealant, the rupture of a C-S bond to form the thiol involves cleavage of the polymer backbone. Continuation of the process leads to degradation of the sealant. These observations have been supported by thermal analysis studies on the poly sulfide sealants and model polymers (511). 

The long-chain polysulfides are stabilised in the solid state by combination with a large counteranion, e.g. (R = alkyl), [Ph4P], [(Ph3P)2N]+ (PPN ). ... 

Many compounds have been tested as ignition quality improvers—additives which shorten the ignition delay to a desirable duration. An extensive review in 1944 (6, 43) listed 303 references, 92 dealing with alkyl nitrates and nitrites 61 with aldehydes, ketones, esters, and ethers 49 with peroxides 42 with aromatic nitro compounds 29, with metal derivatives 28 with oxidation and oxidation products 22 with polysulfides 16 with aromatic hydrocarbons nine with nitration and four with oximes and nitroso compounds. In 1950, tests at the U. S. Naval Engineering Experiment Station (48) showed that a concentration of 1.5% of certain peroxides, alkyl nitrates, nitroaikanes, and nitrocarbamates increased cetane number 20 or more units. 

However, one typical example of a silane, alkyl-substituted silane, silyl azide, silyamine, siloxane and a silane polysulfide polymer, which is or can possibly be used in ordn areas, is presented next. Substituted siloxanes are defined and presented separately under Silicones ... 

Heterocyclic compounds are primarily formed through non-enzymatic browning reactions. Recent studies of deep-fat fried food flavors led to the identification of pyrazines, pyridines, thiazole, oxazoles and cyclic polysulfides which had long-chain alkyl substitutions on the heterocyclic ring. The involvement of lipid or lipid decomposition products in the formation of these compounds could account for the long-chain alkyl substitutions. Model systems were used to study the participation of lipids in the formation of pyrazines, pyridines, thiophenes and cyclic polysulfides. 

The organic polysulfanes described in this article are compounds of the type R-S -R with n > 2 they may be chain-like or cyclic. The organic residues (alkyl or aryl) are linked to the sulfur chain via carbon atoms. These compounds are also known as organic polysulfides. 

Alkylation of an ethanolic solution of sodium sulfide containing an equivalent amount of dissolved sulfur produces disulfides in 60-80% yields from alkyl" or o- and p-nitrophenyl halides." Cyclic disulfides are prepared by alkylation with 1,3-dihalides." Hydroxyl" and nitro" groups do not interfere. Alkylation of a solution of sodium sulfide containing 2-5 equivalents of sulfur produces polysulfides. 

The Willgerodt reaction, which involves heating ketones with ammonium polysulfide, is the most important route to carboxylic acids without degradation of the carbon chain. It applies especially to methyl and alkyl... 

The formulator or the chemist can choose among a large variety of functional silanes with the triethoxysilanol function on one end, the substituents at the other end (Y in Eqs. 1 and 2) can be alkyl, alkylene oxide, isocyanurate, mercapto, polysulfide, amino, ureido, epoxy, isocyanato, vinyl, or methacrylic groups. 

Poly(1,3-phenylene sulfide) also is known and has a decomposition temperature higher than poly(1,4-phenylene sulfide). The same reaction can take place with alkyl dihalides, such as 1,2-dichloroethane. However, since sodium sulfide is very frequently a mixture of sulfide and polysulfides, the polymer structure is better expressed by the formula -(R-Sx-)n- Other reactions are known to lead to polysulfides. For example, poly(phenylene sulfide) can be obtained from 4-chlorothiophenol by self condensation in the presence of a metal base. 

Symmetrical disulfides (73) may be prepared by reaction of alkyl halides with disodium disulfide (Scheme 43). The product is contaminated with triand polysulfides owing to the presence of impurities in the disodium disulfide however, lower members of the series of dialkyl disulfides may be purified by fractional distillation. Disulfides can also be obtained from thiols by mild oxidation, e.g. by treatment with iodine or dimethyl sulfoxide (DMSO) (Scheme 44). In the reaction with iodine, the hydriodic acid formed must be removed, otherwise the disulfide is largely reduced back to the thiol by hydriodic acid which is a powerful reducing agent. Pure unsymmetrical disulfides are more difficult to prepare owing to their tendency to undergo disproportionation they can, however, be synthesised from thiols by treatment with imides (see p. 59) or sulfenyl halides (51) (Scheme 45). 

Carbon disulfide is a valuable synthon (see Chapter 9, p. 147) which can be used for the synthesis of thiocarbonic acid derivatives. Thus, carbon disulfide reacts with ammonium polysulfide or hydrogen sulfide to give trithiocarbonic acid (70) or symmetrical esters (73) after reaction with an alkyl halide. With alkoxides or thiolates, carbon disulfide forms xanthates (77) or S-alkyl trithiocarbonates the latter by further treatment with alkyl, acyl or diazonium halides affords the derivatives (74)-(76) (Scheme 39). 

Willgerodt reaction. In its original form this reaction involved heating an aryl alkyl ketone in a sealed tube at 210-230° with an aqueous solution of yellow ammonium polysulfide, prepared by dissolving sulfur in ammonium sulfide solution. The product is an aryl substituted aliphatic aciil amide, together with some of the corresponding carboxylic acid and often the hydrocarbon. An example is the... 

Most polysulfides with a sulfur rank higher than three, are mixtures where the different sulfur ranks coexist in equilibrium (Table 4). In many cases elemental sulfur is also involved in the above equilibrium. Changes in temperature and pressure sometimes alter this equilibrium and precipitate sulfur. Viscosity of the polysulfides also is a function of temperature, increasing dramatically with decreasing temperature. In most cases heating polysulfides results in their decomposition to the alkyl mercaptans. Some of the aromatic polysulfides are tacky solids. Many trisulfides can be isolated as pure compounds, and exhibit unique chemical properties. They are the only polysulfides that are not corrosive to copper. 

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