Separation and Determination of Sulfur Homocycles by High Pressure Liquid Chromatography—Detection of Novel Sulfur Rings

Abstract

The known sulfur homocycles S, (n=6, 7, 8, 9, 10, 12, 18, 20) which have so far been prepared in pure form were identified and detected by vibrational spectroscopy in mixtures which usually are formed during preparative work-up. Attempts to separate such mixtures by thin-layer (TLC) or column chromatography (CC), led to complete decomposition (TLC), or incomplete separation with partial decomposition to S8 (CC)['l. We have now found that the homocycles S , with n = 6-26 can be separated quantitatively without decomposition by high pressure liquid chromatography (HPLC) and thus detected and determined analytically alongside one another.Since the thermally unstable rings S, (n # 8) rapidly decompose to S8 on S O z and A1203 the only potential method of separation is reversed-phase chromatography on C,*phases (octadecylsilanes). For smaller rings (n c 12), methanol is suitable as eluting agent; for separation of the larger rings cyclohexane must be added up to 30 vol-% owing to their poorer solubility. On using a column of 25 cm length and 3.0 mm internal diameter and a flow rate of 1 cm3/min, a pressure of 40-50 bar is built upfz]. Under these conditions (retention times tR = 2-25 min) no decomposition occurs at 26 "C, as has been established with the particularly unstable s7 (tR = 3 min) and with s20 (tR zz 13 min) (Fig. la).The retention times of the known pure rings unequivocally depend on the atomic number n and so enable identification of the new compounds of the homologous series S, by interor extrapolation. The capacity factors k' are linearly dependent on n in a semilogarithmic plot, but give two straight lines which intercept at n = 9 (Fig. 2). The straight lines obey the regressions logk' = -0.677 + 0.102n (correlation coefficient r=0.994) for s 6 -s 9 and logk'= -0.319+0.064n (r=0.999) for S9-Szo (eluent: methanol/cyclohexane 80/20 vol-%).Suitable for identification of the separated components are the seemingly intense UV absorptions of the sulfur rings at 254 nm, which enable a trace analysis [E254(&) = 59301. Using calibration solutions it could be established that the absorbance of S, (n=7, 8, 10, 12) in the range 0.3-1.8 mg S,/100 cm3 CS2 is a linear function, in case of s 6 a non-linear function of the concentration. We ascribe the non-linearity in the case of S6 to incomplete separation from the solvent CS2, [' I Prof. Allg. Chem., m press. [ " I Sulfur Compounds, Part 74.-Part 73: H.-J. Mausle, R. Steudel, Z . Anorg.ti 3 -Fig. 1. a) Chromatogram of a mixture of S6, S,, Sn. Sto, St2, Stnr and Sz0 prepared from the pure components (eluent: methanoVcyclohexane 80/20 vol-%); h) chromatogram of the higher molecular weight species of sulfur formed from SCI2 and K1 (eluent: methanol/cyclohexane); c) chromatogram of the higher molecular weight S, from an equilibrium sulfur melt which is soluble in CS, (eluent methanol/cyclohexane 69/31 vol-%). n-Fig. 2. Gross retention times tR and logarithm of the capacity factor k = ( f nto)/ to as a function of the atomic number n of sulfur homocycles S. on elution ...

Eine neue Schwefelmodifikation: einfache Synthese voncyclo-S14 aus S8

“…Mit dieser Analysenmethode waren Spuren von S 14 bereits früher in abgeschreckten Schwefelschmelzen und in synthetischen Schwefelmischungen detektiert worden. [9,15] Die cyclische Struktur von S 14 wurde durch eine Einkristall-Röntgenstrukturanalyse nachgewiesen. [16] Da sich Kristalle von S 14 bei Raumtemperatur im Röntgenstrahl rasch zersetzten, wurde die Probe auf À 100 8C gekühlt.…”

Dependence of Conductivity of Polypyrrole Film Doped with p‐Phenol Sulfonate on Solution pH

“…[4] to Fig. Since the C/C~ must be equal to the degree of dissociation of pphenol sulfonate (r), the C/Cs values in the polypyrrole films at arbitrary times were deduced by applying Eq.…”

A multi functional binder with lithium ion conductive polymer and polysulfide absorbents to improve cycleability of lithium–sulfur batteries

“…Sulfur has a strong tendency to catenation, which manifests itself not only in many forms of the element (S n ) but also in polysulfide ion (S n 2À ) [6]. Octasulfur (cyclo-S 8 ) molecule with a crown conformation is the most thermodynamically stable form.…”

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