Pure Sulfanes

The lower members of the polysulfane series with n=2-6 have been prepared as pure compounds, while all members with n values up to 35 have been detected by H-NMR spectroscopy in so-called crude sulfane [31]. The gas-phase structures of the first three members of the polysulfane series are well established from either microwave spectra (H2S2 [32], H2S3 [33]) or high-level ab initio MO calculations (H2S4 [34]). Systematic ab initio studies of the structures, vibrational frequencies and heats of formation of H2S with i up to 6 have also been reported [4, 16]. 

Mixtures of polysulfanes H2S are easy to make and probably occur even naturally but the pure compounds are relatively unstable and can therefore be prepared only with some experimental skills and observing certain technical precautions. Detailed prescriptions exist how to make di-, tri-, tetra-, and higher sulfanes in gram quantities. However, as longer the sulfur chain grows as more difficult it becomes to obtain pure compounds. In general, all... 

The oils from the first reaction can be cracked and fractionated to give pure H2S2 through H2S5. whereas the higher sulfanes are obtained from the other reactions. Although the sulfanes are all thermodynamically unstable with respect to the reactions... 

In general, the sulfanes have a less well-developed chemistry, partly because of the difficulty in isolating them pure, although they have been used for the synthesis of some organosulfur compounds see Sulfur Organic Polysulfanes). 

Polysulfanes with the general formula H2S (n — 2-S) are reactive oils in their pure state. Heating aqueous sulfide solutions yields polysulfide ions most typically with n = 3 or 4. The presence of sulfanes has been used to explain the high concentrations of sulfur compounds in some hydrothermal fluids (Migdisov and Bychkov, 1998). 

Since the aqueous sodium polysulfide contains already several polysulfide anions in equilibrium and since the acidification results in some interconversion reactions, a sulfane mixture H2S c is obtained rather than pure H2S4. This mixture nevertheless reacts in dry CS2/Et20 mixture at 20 °C with dichlorodisulfane, besides other products, to S12 which has been isolated in 4% yield by extraction with CS2 and fractional crystallization [41] ... 

Sulfanes. The compounds H2S2 through H2S6 have been isolated in pure states whereas higher members are so far known only in mixtures. All are reactive yellow liquids whose viscosities increase with chain length. They may be prepared in large quantities by reactions15 such as... 

Thiosulfate (S2O3 ) is composed of an inner sulfonate sulfur (-SO3) and an outer sulfane sulfur (-S), and by expectation, the sulfate produced during disproportionation (Eqn. 12) should be derived from the sulfonate sulfur, whereas sulfide should be derived from the sulfane sulfur. Isotope fractionation during thiosulfate disproportionation has been explored with pure bacterial cultures under two contrasting experimental circumstances. In one case, sulfide, a byproduct of the disproportionation process, was allowed to accumulate within the experimental system (Habicht et al. 1998) whereas in the other case sulfide was actively purged from the experimental system and never reached a concentration greater than 0.4 mM (Cypionka et al. 1999). 

All reactions with sulfanes must be protected from moisture, and pure starting materials must be used. 

The procedure for making SO -solvent complex from fuming sulfuric acid is more complicated, but less likely to arouse suspicion since fuming sulfuric acid has a lot more uses than Sulfan. It is also far more likely to be available via the five-finger discount method. Fuming sulfuric acid comes in a variety of strengths, but the ACS reagent contains 30% SO3 or oleum. Pure SO boils at 45 °C, and at room temperature has a vapor pressure of over 400 mm Hg. That is why the stuff fumes, and why the stuff can be removed from the sulfuric acid... 

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