Sulfur monochlorid

This simplified method gives 2-aminothiazole in good yield (50 to 70%) (311, 330), Other reactants can replace iodine, for example, chlorine, bromine, sulfuryl chloride, chlorosulfonic acid, or sulfur monochloride also give good results. 

Niobium Pent chloride. Niobium pentachloride can be prepared in a variety of ways but most easily by direct chlorination of niobium metal. The reaction takes place at 300—350°C. Chlorination of a niobium pentoxide—carbon mixture also yields the pentachloride however, generally the latter is contaminated with niobium oxide trichloride. The pentachloride is a lemon-yeUow crystalline soHd that melts to a red-orange Hquid and hydrolyzes readily to hydrochloric acid and niobic acid. It is soluble in concentrated hydrochloric and sulfuric acids, sulfur monochloride, and many organic solvents. 

Physical Properties. Sulfur monochloride [10025-67-9] S2CI2, is a yeUow-orange Hquid with a characteristic pungent odor. It was first discovered as a chlorination product of sulfur in 1810. Table 5 provides a Hst of the physical properties. 

Table 5. Physical and Thermodynamic Properties of Sulfur Monochloride, S2CI2...

Chemical Properties. The chemistry of the sulfur chlorides has been reviewed (141,142). Sulfur monochloride is stable at ambient temperature but undergoes exchange with dissolved sulfur at 100°C, indicating reversible dissociation. When distilled at its atmospheric boiling point, it undergoes some decomposition to the dichloride, but decomposition is avoided with distillation at ca 6.7 kPa (50 mm Hg). At above 300°C, substantial dissociation to S2 and CI2 occurs. Sulfur monochloride is noncombustible at ambient temperature, but at elevated temperatures it decomposes to chlorine and sulfur (137). The sulfur then is capable of burning to sulfur dioxide and a small proportion of sulfur trioxide. 

Sulfur monochloride is hydrolyzed at a moderate rate by water at room temperature but rapidly at higher temperatures. In the vapor state, the hydrolysis rate is slow and involves disproportionation of the primary hydrolysis products ... 

Various reducing agents, eg, hydrogen iodide, can abstract chlorine from sulfur monochloride leaving elemental sulfur ... 

Sulfur trioxide [7446-11-9] reacts with sulfur monochloride to produce pyrosulfuryl chloride [7791-27-7] CISO2OSO2CI. 

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 ... 

Sulfurized olefins (S2CI2 plus isobutene) are further reacted with S and Na2S to give products useful as extreme pressure lubricant additives (144,145). The reaction of unsaturated natural oils with sulfur monochloride gives resinous products known as Factice, which are useful as art-gum erasers and mbber additives (146,147). The addition reaction of sulfur monochloride with unsaturated polymers, eg, natural mbber, produces cross-links and thus serves as a means for vulcanizing mbber at moderate temperatures. The photochemical cross-linking of polyethylene has also been reported (148). 

Using sulfur trioxide plus chlorine, or sulfur dioxide plus chlorine, sulfur monochloride yields thionyl chloride [7719-09-7] SOCI2. Various nucleophilic reactions can displace the chlorine atoms of sulfur monochloride ... 

Ma.nufa.cture. Sulfur monochloride is made commercially by direct chlorination of sulfur, usually in a heel of sulfur chloride from a previous batch. The chlorination appears to proceed stepwise through higher sulfur chlorides (S Cl2, where x > 2). If conducted too quickly, the chlorination may yield products containing SCI2 and S Cl2 as well as S2CI2. A catalyst, eg, iron, iodine, or a trace of ferric chloride, faciUtates the reaction. The manufacture in the absence of Fe and Fe salts at 32—100°C has also been reported (149—151). 

The commercial manufacture of carbon tetrachloride by chlorination of carbon disulfide yields sulfur monochloride. 

The sulfur monochloride formed in this reaction can be treated with additional carbon disulfide in the presence of a catalyst to yield carbon tetrachloride and sulfur. Alternatively, the sulfur monochloride and carbon tetrachloride can be... 

Shipment nd Stora.ge, Sulfur monochloride is minimally corrosive to carbon steel and iron when dry. If it is necessary to avoid discoloration caused by iron sulfide formation or chloride stress cracking, 310 stainless steel should be used. Sulfur monochloride is shipped in tank cars, tank tmcks, and steel dmms. When wet, it behaves like hydrochloric acid and attacks steel, cast iron, aluminum, stainless steels, copper and copper alloys, and many nickel-based materials. Alloys of 62 Ni—28 Mo and 54 Ni—15 Cr—16 Mo are useful under these conditions. Under DOT HM-181 sulfur monochloride is classified as a Poison Inhalation Hazard (PIH) Zone B, as well as a Corrosive Material (DOT Hazard Class B). Shipment information is available (140). 

Sulfur monochloride also reacts with substituted phenols to give condensation products useful for mbber compounding (qv) (150). Elf Atochem NA manufactures products known as Vultacs by the reaction of amylphenols and sulfur monochloride (153). 

Sulfur monochloride can act as a chlorinating agent in some reactions. For example, 0,0-diaLkyl phosphorodithioic acids [756-80-9] are converted to 0,0-diaLkylphosphorochloridothioate ... 

The principal commercial uses of sulfur monochloride are in the manufacture of lubricant additives and vulcanising agents for mbber (147,154,155) (see Lubrication AND lubricants Rubber chemicals). The preparation of additives for wear and load-bearing improvement of lubricating oils is generally carried out in two steps and the technology is described in numerous patents (155) (see Sulfurization and sulfchlorination). 

Economic Aspects. The price of sulfur monochloride in 1995 was 0.25 /kg bulk. 

Health and Safety Factors. Sulfur monochloride is highly toxic and irritating by inhalation, and is corrosive to skin and eyes (156). The OSHA permissible exposure limit is 1 ppm (6 mg/m ). Pulmonary edema may result from inhalation. Because its vapor cannot be tolerated even at low concentrations, its presence serves as a warning factor. Sulfur monochloride is not highly flammable, having flash poiats of 118°C (closed-cup) and 130°C (open-cup) and an auto-ignition temperature of 234°C. 

Chemical Properties. Sulfur dichloride ia the Hquid state at ambient temperature is ia equiHbrium with sulfur monochloride and dissolved... 

Sulfur dichloride undergoes many of the same reactions with organic compounds as described for sulfur monochloride. Addition to olefins affords a route to bis(2-chloroalkyl) sulfides and, ia certain cases, heterocycHc sulfides (159,160). 

Manufacture. The manufacture of sulfur dichloride is similar to that of sulfur monochloride, except that the last stage of chlorination proceeds slowly and must be conducted at temperatures below 40°C. The preparation of a high assay sulfur dichloride requites special techniques, eg, continuous chlorination duriag distillation or distillation with traces of phosphoms trichloride or phosphoms pentasulfide [1314-80-3] (162—164). Cmde product containing 80 wt % sulfur dichloride to which is added 0.1 wt % phosphoms trichloride can be distilled to yield a 98—99 wt % pure sulfur dichloride, which can be stored for weeks at room temperature without appreciable change. 

The sulfur dichloride can be fed as such or produced directiy in the reactor by reaction of chlorine with sulfur monochloride. 

In a batch process (176), a glass-lined jacketed iron vessel is charged with either sulfur monochloride or sulfur dichloride and about 1% of antimony trichloride as a catalyst. Chlorine is introduced into the reactor near the bottom. Liquid oleum is added to the reactor at such a rate that the temperature of the reaction mass is held at ca 25°C by the use of cooling water in the jacket. 

In another process sulfur monochloride, sulfur dioxide, and chlorine are allowed to react at 200°C in the presence of an activated carbon catalyst... 

At present, thionyl chloride is produced commercially by the continuous reaction of sulfur dioxide (or sulfur trioxide) with sulfur monochloride (or sulfur dichloride) mixed with excess chlorine. The reaction is conducted in the gaseous phase at elevated temperature over activated carbon (178). Unreacted sulfur dioxide is mixed with the stoichiometric amount of chlorine and allowed to react at low temperature over activated carbon to form sulfuryl chloride, which is fed back to the main thionyl chloride reactor. 

The decomposition of sulfuryl chloride is accelerated by light and catalyzed by aluminum chloride and charcoal. Many of the reactions of sulfuryl chloride are explainable on the basis of its dissociation products. Sulfuryl chloride reacts with sulfur at 200°C or at ambient temperature in the presence of aluminum chloride producing sulfur monochloride. It hberates bromine or iodine from bromides or iodides. Sulfuryl chloride does not mix readily with water and hydrolyzes rather slowly. 

However, when sulfur monochloride is used as the catalyst, chlorosulfites form. 

Sulfur Products Handbook on Sulfur Monochloride and Sulfur Chloride, Bulletin SPE-SUL-HB 10/9, Oxychem Basic Chemicals Group, Occidental Chemical Corp., Dallas, Tex., 1993, p. 3. 

Sulfur monochloride [10025-67-9] S2CI2, and sulfur dichloride,SCl2, react with unsaturated materials, forming products that are cross-linked by sulfur but which also contain chlorine (eq. 7) (10). 

The sulfur chlorides give higher xanthate sulfides. For example, the following product is obtained from sulfur monochloride and an ether suspension at room temperature ... 

Arsenic trichloride (arsenic(III) chloride), AsQ. is the most common and important haUde of arsenic. It may be formed by spontaneous combination of the elements and, in addition, by the following reactions (/) chlorine with arsenic trioxide (2) sulfur monochloride, 82(11, or a mixture of S2CI2 chlorine, with arsenic trioxide and (J) arsenic trioxide with concentrated hydrochloric acid or with a mixture of sulfuric acid and a chloride. 

Carbon disulfide and chlorine react in the presence of iron catalysts to give carbon tetrachloride [56-23-5] and sulfur monochloride [10025-67-9] ... 

This is foUowed by a second reaction where sulfur monochloride becomes the chlorinating agent ... 

Benzotrichloride with zinc chloride as catalyst reacts with ethylene glycol to form 2-chloroethyl benzoate [7335-25-3] (35). Perchlorotoluene is formed by chlorination with a solution of sulfur monochloride and aluminum chloride in sulfuryl chloride (36). 

Sodium ethoxide is used in organic synthesis as a condensing and reducing agent. The reaction between sodium ethoxide and sulfur monochloride yields diethyl thiosulfite (19). 

The direct formation of dipyrimidin-5-yl sulfides occurs on treatment of appropriate 5-unsubstituted pyrimidine substrates with sulfur mono- or di-chloride. Thus, reaction of uracil (83 R = H) with sulfur monochloride in boiling formic acid gives diuracil-5-yl sulfide in good yield sulfur dichloride gives a poor yield. Simple derivatives of uracil and barbituric acid undergo similar reactions but not cytosine, isocytosine, 2,4-bismethylthiopyrimidine or pyrimidine-4,6-dione (59). The mechanism is unknown (72AJC2275). 

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