Abstract:A large number of 1,n‐bis(alkylthio)alkanes, R′S(CH2)nSR″, was investigated by pulse radiolysis in aqueous solutions. The sulphur‐centred radical cations, which were obtained on oxidation of the dithia compounds by ·OH radicals, are stabilized via 2σ/1σ* three‐electron interaction between two sulphur atoms. Intramolecular stabilization is the only process observed for n = 2–4, whereas for longer chain compounds with n > 4 some intermolecular sulphur–sulphur interaction is also indicated. The stability and yiel… Show more
“…Kishore and Asmus 27 used the pulse radiolysis technique and reported the spectrum in the form of G × ε vs wavelength ( G denotes the number of species generated or transformed per 100 eV energy uptake and is approximately 2.8 in their work). They reported a maximum absorbance at 390 nm and estimated a peak extinction coefficient in the range of 5000−7000 M -1 cm -1 ; they also pointed out that this is a typical extinction coefficient range for the structurally similar >S∴X type and other three-electron-bonded radical species. ,− 5 Absorption spectra of the DMSO−Cl adduct from this work (solid circles) and from the study of Kishore and Asmus 27 (open circles). …”
Section: Resultsmentioning
confidence: 57%
“…They reported a maximum absorbance at 390 nm and estimated a peak extinction coefficient in the range of 5000-7000 M -1 cm -1 ; they also pointed out that this is a typical extinction coefficient range for the structurally similar >S∴X type and other threeelectron-bonded radical species. 27,[61][62][63] Analysis of Systematic Errors. Derivation of rate coefficients for DMSO, DMSO 2 , and MS reactions with Cl and Cl 2employed eq 3, so the equilibrium constant (K 3 ) for Cl + Cla Cl 2 -(R3, R-3) is an important parameter in this kinetics study.…”
A laser flash photolysis-long path UV-visible absorption technique has been employed to investigate the kinetics of aqueous phase reactions of chlorine atoms (Cl) and dichloride radicals (Cl2(-)) with four organic sulfur compounds of atmospheric interest, dimethyl sulfoxide (DMSO; CH3S(O)CH3), dimethyl sulfone (DMSO2; CH3(O)S(O)CH3), methanesulfinate (MSI; CH3S(O)O-), and methanesulfonate (MS; CH3(O)S(O)O-). Measured rate coefficients at T = 295 +/- 1 K (in units of M(-1) s(-1)) are as follows: Cl + DMSO, (6.3 +/- 0.6) x 10(9); Cl2(-) + DMSO, (1.6 +/- 0.8) x 10(7); Cl + DMSO2, (8.2 +/- 1.6) x 10(5); Cl2(-) + DMSO2, (8.2 +/- 5.5) x 10(3); Cl2(-) + MSI, (8.0 +/- 1.0) x 10(8); Cl + MS, (4.9 +/- 0.6) x 10(5); Cl2(-) + MS, (3.9 +/- 0.7) x 10(3). Reported uncertainties are estimates of accuracy at the 95% confidence level and the rate coefficients for MSI and MS reactions with Cl2(-) are corrected to the zero ionic strength limit. The absorption spectrum of the DMSO-Cl adduct is reported; peak absorbance is observed at 390 nm and the peak extinction coefficient is found to be 5760 M(-1) cm(-1) with a 2sigma uncertainty of +/-30%. Some implications of the new kinetics results for understanding the atmospheric sulfur cycle are discussed.
“…Kishore and Asmus 27 used the pulse radiolysis technique and reported the spectrum in the form of G × ε vs wavelength ( G denotes the number of species generated or transformed per 100 eV energy uptake and is approximately 2.8 in their work). They reported a maximum absorbance at 390 nm and estimated a peak extinction coefficient in the range of 5000−7000 M -1 cm -1 ; they also pointed out that this is a typical extinction coefficient range for the structurally similar >S∴X type and other three-electron-bonded radical species. ,− 5 Absorption spectra of the DMSO−Cl adduct from this work (solid circles) and from the study of Kishore and Asmus 27 (open circles). …”
Section: Resultsmentioning
confidence: 57%
“…They reported a maximum absorbance at 390 nm and estimated a peak extinction coefficient in the range of 5000-7000 M -1 cm -1 ; they also pointed out that this is a typical extinction coefficient range for the structurally similar >S∴X type and other threeelectron-bonded radical species. 27,[61][62][63] Analysis of Systematic Errors. Derivation of rate coefficients for DMSO, DMSO 2 , and MS reactions with Cl and Cl 2employed eq 3, so the equilibrium constant (K 3 ) for Cl + Cla Cl 2 -(R3, R-3) is an important parameter in this kinetics study.…”
A laser flash photolysis-long path UV-visible absorption technique has been employed to investigate the kinetics of aqueous phase reactions of chlorine atoms (Cl) and dichloride radicals (Cl2(-)) with four organic sulfur compounds of atmospheric interest, dimethyl sulfoxide (DMSO; CH3S(O)CH3), dimethyl sulfone (DMSO2; CH3(O)S(O)CH3), methanesulfinate (MSI; CH3S(O)O-), and methanesulfonate (MS; CH3(O)S(O)O-). Measured rate coefficients at T = 295 +/- 1 K (in units of M(-1) s(-1)) are as follows: Cl + DMSO, (6.3 +/- 0.6) x 10(9); Cl2(-) + DMSO, (1.6 +/- 0.8) x 10(7); Cl + DMSO2, (8.2 +/- 1.6) x 10(5); Cl2(-) + DMSO2, (8.2 +/- 5.5) x 10(3); Cl2(-) + MSI, (8.0 +/- 1.0) x 10(8); Cl + MS, (4.9 +/- 0.6) x 10(5); Cl2(-) + MS, (3.9 +/- 0.7) x 10(3). Reported uncertainties are estimates of accuracy at the 95% confidence level and the rate coefficients for MSI and MS reactions with Cl2(-) are corrected to the zero ionic strength limit. The absorption spectrum of the DMSO-Cl adduct is reported; peak absorbance is observed at 390 nm and the peak extinction coefficient is found to be 5760 M(-1) cm(-1) with a 2sigma uncertainty of +/-30%. Some implications of the new kinetics results for understanding the atmospheric sulfur cycle are discussed.
“…The various λ max of the long-lived absorption are listed in Table . For comparison, absorption maxima are also listed for the intramolecular S∴S-bonded radical cations generated upon oxidation of RS(CH 2 ) n SR‘. ,, The excellent agreement of the optical transition energies is taken as proof for the identical structure of the transients. This conclusion is further corroborated by a lack of concentration dependence on the transient's yield, contrasting the situation typically prevailing for the formation of intermolecular 3-e species.…”
Section: Resultsmentioning
confidence: 99%
“…b Data from ref . c G (μmoles per 10 J absorbed energy) calculated on the basis of reported extinction coefficients (ref ), and an estimated G (H • ) = 3.4. d G based on G ( • OH) = 6.0.…”
Section: Resultsmentioning
confidence: 99%
“… a Experiments perfomed with N 2 -purged solutions containing 0.01 M sulfinyl sulfide, 1 M 2-methyl-2-propanol, and 3 M HClO 4 . b Data from ref . c G (μmoles per 10 J absorbed energy) calculated on the basis of reported extinction coefficients (ref ), and an estimated G (H • ) = 3.4. d G based on G ( • OH) = 6.0. …”
The reaction of H-atoms with sulfinyl sulfides RS(CH2)
n
SOR‘ (R, R‘ = alkyl) in strongly acidic aqueous
medium leads, among other reactions, to the reduction of the sulfoxide moiety. This results in the formation
of a S•+ radical cation entity which coordinates with the original sulfide moiety to yield the (>S∴S<)+
three-electron-bonded 2σ/1σ* radical cation. The optical properties of this reductively generated species are
identical to those for the transients obtained previously upon one-electron oxidation of dithiaalkanes. At sulfinyl
sulfide concentrations in the 10-4−10-2 M range the H•-atom-induced process occurs intramolecularly. The
most stable three-electron-bonded radical cation is formed when the two interacting sulfurs are linked via a
−(CH2)3− chain and a five-membered ring structure can be established. The yields of the (>S∴S<)+-type
transients range from G = 0.2−0.7 (species per 10 J absorbed energy) with the high value pertaining to the
reduction of MeS(CH3)3SOMe (0.01 M) in aqueous, N2-purged, 3 M HClO4 solutions. These yields are
significantly below the yield of H•-atoms, indicating competing processes such as H-atom abstraction and
reaction of H• with 2-methyl-2-propanol (which was added for removal of •OH radicals). The rate constant
estimate of (1.8 ± 0.2) × 107 M-1 s-1 for the reaction of H• +MeS(CH2)3SOMe appears to be typical with
respect to the order of magnitude for the H•-induced reduction of the sulfoxide moiety. Electrochemical cyclic
voltammetry experiments on the oxidation of RS(CH2)
n
SR‘, RS(CH2)
n
SOR‘, RSO(CH2)
n
SOR‘, and RS(CH2)
n
SO2R‘ showed relatively little influence of the sulfur-linking alkyl chain length and the nature of the terminal
alkyl substituents except for the dithiaalkanes. This may indicate the lack of any significant electronic interaction
between the S and SO moieties in the alkylsulfinyl sulfides, SO and SO, in the bis(alkylsulfinyl)alkanes, and
S and SO2 in the alkylsulfonyl sulfides. The electrochemical data further suggest that, concerning RS(CH2)
n
SOR‘, the lower oxidation potential pertains to the oxidation of the sulfide moiety (yielding RSO(CH2)
n
SOR‘). The SO → SO2 oxidation, on the other hand, requires potentials which are more positive by about 0.2
V. It appears that the RS(CH2)3SOR‘ → RS(CH2)3SO2R‘ oxidation prevails when R‘ is electron density releasing,
while an electron density releasing R favors the RS(CH2)
n
SOR‘ → RSO(CH2)3SOR‘ oxidation.
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