Dimethyl sulfide spectroscopy

More recently, this method has been extended to preparation of a variety of disulfonium dications from both acyclic and cyclic bis-sulfides, including very labile dications not observed when other methods were used.78 Thus, simple acyclic S-S dications were prepared by an intermolecular reaction of a monosulfide, a monosulfoxide and triflic anhydride.79 In the first step, reaction of triflic anhydride with dimethylsulfoxide generates a highly electrophilic80 complex 50 (dimethyl sulfide ditriflate).81 The latter reacts with dimethyl sulfide to give labile tetramethyldisulfonium dication 51 identified by NMR spectroscopy.79 In a similar manner, bis-(tetramethylene)disulfonium dication 52 is obtained from tetrahydrothiophene and its S-oxide (Scheme 17). 

PE spectroscopy indicates that thietane has a first ionization potential (8.67 eV) only slightly larger than that of dimethyl sulfide (8.65 eV) and significantly lower than that of... 

Block et al.194 examined the effects of trimethylsilyl substitution on the first vertical ionization potentials by photoelectron and Penning ionization electron spectroscopy studies of a range of cyclic and noncyclic sulfides and ethers. It was shown that substitution of oxirane 218 with a trimethylsilyl substituent as in 219 lowered the ionization potential by 0.90 eV (20.8 kcal/mol), while similar substitution of dimethyl ether 220 in 221 lowered the ionization potential by 0.64 eV (14.8 kcal/mol). By comparison, the effects of silyl substitution on sulfur lone-pair ionization potentials was found to be smaller thus the ionization potential of dimethyl sulfide 222 is lowered by 0.37 eV upon trimethylsilyl substitution in 223, and the trimethylsilyl-substituted thiirane 225 is lowered by 0.59 eV relative to thiirane 224. The raising of the energy of the sulfur lone-pair electrons in the thiirane 225 is also apparent from its UV spectrum, where there is a bathochromic shift in the absorption maximum compared to the parent 224. 

The FT-Raman spectra of the sulfur vulcanisates of the various model olefins do not contain the characteristic disulfide signal at 510 cm"1, but do contain the typical higher sulfide bands at 490, 460 and 440 cm"1 (Table 6.2). In addition, a new band at about 475 cm 1 is observed for the vulcanisates of 2-methyl-2-pentene and 3-hexene, which has not yet been assigned (hexasulfide ). Results of HPLC analysis have shown that the vulcanisate of 2,3-dimethyl-2-butene consists mainly of a mixture of disulfide to pentasulfide with about 15 mole% of disulfide [79]. This illustrates that FT-Raman spectroscopy is not very sensitive for the identification of disulfides. Because of an overlap of signals, FT-Raman does not provide detailed, quantitative information on the presence of the individual higher sulfides (S>2). 

Dezamaud-Dandine C, Boumel F, Mangeney C, Tronc M, Jones D, Modelli A (1998) a resonances in electron transmission (ETS) and X-ray absorption (XAS) spectroscopies of dimethyl(poly)sulphides (CH3)2SX (x = 1,2,3). J Phys B At Mol Opt Phys 31 L497-L502 Dezamaud-Dandine C, Boumel F, Mangeney C, Tronc M, Modelli A, Jones D (2001) Empty levels probed by XAS and ETS in cyclic polymethylene sulfides (CH2)nS, n = 2,3,4,5 Chem Phys 265 105-112 Egerton R (1997) Electron energy-loss spectroscopy. Phys World 10 47-51... 

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