Monosulfide C S

Fig. 5.1 Sample IJs) curves for various vibrational states of carbon monosulfide, C = S. These curves were calculated2 in accordance with Eq. (5.2), using i )y(r) functions obtained by solving Schrodinger s equation with an experimental potential energy surface derived from molecular spectroscopy.

Fig. 5.2 Radial distribution curves, Pv

To sum up it can be said that all monosulfides C =S with n = 1-4 have been matrix-isolated and identified. The next member C5S has been prepared by electric discharge in a mixture of CS2, C2H2 and argon and observed by its rotational spectrum.149 The expected multiplicities and spectral data121,122,150 are verified by the experimental observations. 

The S-S linkage of disulfides and the C-S linkage of certain sulfides can undergo photoinduced homolysis. The low reactivity of the sulfur-centered radicals in addition or abstraction processes means that primary radical termination can be a complication. The disulfides may also be extremely susceptible to transfer to initiator (Ci for 88 is ca 0.5, Sections 6.2.2.2 and 9.3.2). However, these features are used to advantage when the disulfides are used as initiators in the synthesis of tel ec he lies295 or in living radical polymerizations. 96 The most common initiators in this context are the dithiuram disulfides (88) which are both thermal and photochemical initiators. The corresponding monosulfides [e.g. (89)J are thermally stable but can be used as photoinitiators. The chemistry of these initiators is discussed in more detail in Section 9.3.2. 

Tetraethylthiuram disulfide (13) induces St polymerization by the photodissociation of its S-S bond to give the polymer with C-S bonds at both chain ends (15). The C-S bond further acts as a polymeric photoiniferter, resulting in living radical polymerization. Eventually, some di- or monosulfides, as well as 13, were also examined as photoiniferters and were found to induce polymerization via a living radical polymerization mechanism close to the model in Eq. (18), e.g., the polymerization of St with 35 and 36 [76,157]. These disulfides were used for block copolymer synthesis [75,157-161] ... 

In addition to carbon disulfide (odorless when pure), carbon subsulfidc, —C—C—C—S, an evil-smelling red oil and carbon monosulfide, (CSX), are known as well as COS, CSSe and CSTe. Because of its similarity to oxygen, and the reactivity of its acids, sulfur enters widely into organic compounds. 

CS2, the analogue of C02, reacts with e aq at a faster rate (k = 3.1 0.3 X 1010 M-1 sec.-1) (68) which is diffusion controlled. It is not surprising that the C=S bond is more reactive toward e aq than the carbonyl bond, since the lower electronegativity of the sulfur atom makes its additional orbitals more liable to accommodate an additional electron. It is very likely that a long lived CS2- is produced, which eventually is reduced to carbon monosulfide however this requires verification. It... 

Chen and co-workers tentatively assigned new signals in the FT-IR spectra of accelerated sulfur-vulcanised NR to the formation of C-S and S-S bonds corresponding to monosulfides, disulfides and polysulfides [68]. The vulcanisation of NR was retarded when clay was added to the NR compound. 

The monosulfide, Fc-S-Fc, was first prepared in 1961 by Rausch [48] by reaction of the thiolate Fc-SNa with iodoferrocene, Fc-I, in the presence of copper bronze at 150 °C. The disulfide, Fc-SS-Fc, had been obtained independently by Knox and Pauson [81] and by Nesmeyanov et al. [82] at an even earlier date (1958) by aerial oxidation of mercaptoferrocene, Fc-SH hydrolytic cleavage of ferrocenyl thiocya-... 

Qualitative photochemical studies of a variety of simple alkyl monosulfides are consistent with primary C-S cleavage... 

In cystine, another common amino acid, S exhibits S-S and C-S linkages, and its NEXAFS spectra exhibit two distinct peaks separated by about 1.5 eV (Fig. 25). These two peaks correspond to the S l.v— a transitions of S-S and C-S bonds at low and high energies, respectively. Examination of a series of dimethyl polysulfides also exhibits the same spectral features (Fig. 33 Derzanaud-Dandine et al. 1998). Dimethyl monosulfide exhibits an intense feature at 2473.1 eV, and dimethyl disulfide and dimethyl trisulfide exhibit a doublet that corresponds to the 1. v—>g transitions of S-S and C-S at 2472.2 and... 

Because of the excitation of electrons in nonbonded orbitals, saturated molecules that contain atoms with lone pairs of electrons exhibit electronic transitions at longer wavelengths than the corresponding saturated hydrocarbons. Thus, alkyl iodides and monosulfides containing the C-S-C linkage give n a transitions near 260 and 215 nm, respectively. 

The transfer coefficients of disulfides are extremely low for styrene and methyl methacrylate (see Table 4), but are close to one for the vinyl acetate polymerization. In general the xanthogens and thiurams have higher chain transfer ability, which has been attributed to the iniferter mechanism described above. Monosulfides have lower transfer coefficients in comparison to disulfides. This may refiect steric factors and the relative strength of the C—S bond, which is significantly stronger than the S—S bond. 

The next higher homolog of this series, C6S2, has been discovered in the gas phase . While carbonyl sulfide is a well known stable molecule, the higher sulfide oxides 0=(C) =S are also of recent vintage, and they were obtained by matrix isolation. For example, C2OS 2 was matrix isolated by generating it in the photochemical reaction of carbon monosulfide with carbon monoxide . 

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