Detection of interstellar HCS and its metastable isomer HSC: new pieces in the puzzle of sulfur chemistry

We present the first identification in interstellar space of the thioformyl radical (HCS) and its metastable isomer HSC. These species were detected toward the molecular cloud L483 through observations carried out with the IRAM 30 m telescope in the λ3 mm band. We derive beam-averaged column densities of 7 × 1012 cm−2 for HCS and 1.8 × 1011 cm−2 for HSC, which translate into fractional abundances relative to H2 of 2 × 10−10 and 6 × 10−12, respectively. Although the amount of sulfur locked by these radicals is low, their detection allows placing interesting constraints on the chemistry of sulfur in dark clouds. Interestingly, the H2CS/HCS abundance ratio is found to be quite low, ~1, in contrast with the oxygen analog case, in which the H2CO/HCO abundance ratio is around 10 in dark clouds. Moreover, the radical HCS is found to be more abundant than its oxygen analog, HCO. The metastable species HOC, the oxygen analog of HSC, has not yet been observed in space. These observational constraints are compared with the outcome of a recent model of the chemistry of sulfur in dark clouds. The model underestimates the fractional abundance of HCS by at least one order of magnitude, overestimates the H2CS/HCS abundance ratio, and does not provide an abundance prediction for the metastable isomer HSC. These observations should prompt a revision of the chemistry of sulfur in interstellar clouds.

Benzotrifuran (BTFuran): a building block for π-conjugated systems

Reported here is the first synthesis, X-ray crystal structure, and derivatization of C3h-symmetric benzotrifuran (BTFuran), oxygen analog of the widely exploited benzotrithiophene.

Pyrithione-based ruthenium complexes as inhibitors of aldo–keto reductase 1C enzymes and anticancer agents

Four ruthenium complexes of clinically used zinc ionophore pyrithione and its oxygen analog were evaluated as inhibitors of aldo–keto reductases 1C.

The acid dissociation constant of triphenylethenethiol, a simple thioenol, and that of its oxygen-enol analog

The acidity constant, pQaE = 8.49, for the stable thioenol, triphenylethenethiol, was determined by spectrophotometric titration, and that, pQaE = 11.37, for its unstable oxygen analog, triphenylethenol, was determined by analysis of its ketonization rate using enol generated flash photolytically from triphenylvinyl bromide. (These acidity constants are concentration quotients applicable at 0.10 M ionic strength in 50 vol.% aqueous methanol.) This appears to be the first determination of the acid strength of a simple thioenol. Triphenylethenethiol was unreactive in dilute acid or base, but in concentrated perchloric acid solutions it was slowly transformed into diphenylacetophenone and 2,3-diphenylbenzo[b]thiophene; the mechanisms of these reactions are believed to involve rapid equilibrium protonation of the enol on the beta -carbon followed by rate-determining capture of the cation so formed, either externally by solvent or internally by one of the beta -phenyl groups of the ion.Key words: enol ketonization, thioenol, flash photolysis, vinyl halide.