- HCl Elimination from Ethanesulfenyl Chloride and Chlorodimethyl Sulfide
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Thioacetaldehyde (5) is prepared by matrix photolysis of ethanesulfenyl chloride (3) or thiirane (4) and by flash pyrolysis of allyl ethyl sulfide (6).Matrix irradiation of 3 or 5 with 222-nm light results in a dehydrogenation, and a mixture of thiirene (7), ethynethiol (8), and thioketone (9) is formed.Flash pyrolysis of chlorodimethyl sulfide ((1) yields ethenethiol (11) together with thiirane (4), whereas ethanesulfenyl chloride (2) gives ethene under the same conditions.The identification of thioacetaldehyde (5) is based on the comparison between the experimental and calculated IR spectra. Key Words: Matrix isolation / Elimination of HCl, photochemically / Flash pyrolysis / Calculations, ab initio / Photochemistr
- Maier, Guenther,Floegel, Ulrich,Reisenauer, Hans Peter,Hess, B. Andes,Schaad, Lawrence J.
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p. 2609 - 2612
(2007/10/02)
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- Photochemistry of Low-Temperature Matrices Containing Carbonyl Sulfide: Reactions of Sulfur Atoms with the Phosphorus Trihalides PF3 and PCl3 and the Hydrocarbons CH4, C2H4, and C2H2
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Exposure of a solid argon matrix containing the molecules OCS and PX3 (X = F or Cl) at ca. 20 K to broad-band ultraviolet radiation leads to the formation of CO and the corresponding thiophosphorus(V) halides SPX3, as witnessed by the infrared spectrum of the matrix.Photolysis of a solid methane matrix containing OCS at 13-20 K on exposure to radiation with wavelengths near 230 nm gives rise to CO, methanethiol, CH3SH, thioformaldehyde, H2C=S, and carbon disulfide, CS2, as the only products to be detected by their infrared spectra.Yet there is no sign of either CH3SH or H2C=S on photolysis of OCS in a CH4-doped argon matrix with the composition Ar:CH4:OCS = 100:20:1.Evidently the photolysis of OCS generates 1D sulfur atoms which add to an adjacent CH4 molecule with the formation of a vibrationally activated intermediate *; this relaxes to give CH3SH or decomposes to give H2C=S.Similar experiments have been carried out with solid argon matrices including OCS and either C2H4 or C2H2.In the presence of C2H4 there is no hint of C-H insertion; instead the C2H4 undergoes sulfur atom addition at the double bond to give thiirane, , as the sole product to be identified by its infrared spectrum.By contrast, C2H2 yields thioketene, H2C=S, ethynethiol, HCCSH, and carbon disulfide, CS2, as the main products, as well as thiirane, , as a minor product.The response of the hydrocarbon molecules in argon matrices can be interpreted in terms of the diffusion and reaction of ground-state 3P sulfur atoms but not of 1D sulfur atoms which are too short-lived to undergo significant migration.It appears that 3P sulfur atoms react with both C2H4 and C2H2 to yield a triplet diradical: that derived from C2H4 favors cyclization, whereas that derived from C2H2 rearranges preferentially to H2C=C=S and this in turn enters into secondary reactions to give HCCSH and CS2.
- Hawkins, Michael,Almond, Matthew,Downs, Anthony J.
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p. 3326 - 3334
(2007/10/02)
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- Characterization of Matrix-Isolated Antiaromatic Three-Membered Heterocycles. Preparation of the Elusive Thiirene Molecule
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The preparation and characterization of thiirene (4), a heterocyclic analogue of cyclobutadiene (1), which is derived from the photolysis of 1,2,3-thiadiazole (5), is described.The methodology exploits the C2v symmetry of the species 4 and utilizes isotopic labeling to aid in the characterization and narrow band-pass filters to protect thiirene from reaction with light of λ > 2700 Angstroem, when it is generated photochemically.The evidence for 4 is based on (1) the fact that the same monolabeled species X is formed from distinctly labeled -1,2,3-thiadiazoles, (2) the photoisomerization of labeled X to ethynyl mercaptan and thioketene both with randomized label, and (3) the likelihood that the observed infrared bands attributed to 4 belong to a single species possessing cyclopropenoid character.In addition to thiirene, ethynyl mercaptan (14) and thioketene (15) are derived from 5.There are thus two paths (λ > 2900 Angstroem) originating from 5 which give rise to 14 and 15.One stems from thiadiazole without the intervention of 4 and does not scramble hydrogens or carbons; the other is mediated by thiirene, which necessarily makes the C-H bonds equivalent.Irradiation (λ ca. 3500 Angstroem) of doubly labeled thiirene gives all four possible ethynyl mercaptans, indicating at least one exchange of hydrogens between carbon atoms must occur.The most reasonable explanation for this exchange presumes that both hydrogens reside on a single carbon atom at some point during the photoisomerization of thiirene to ethynyl mercaptan (14).
- Krantz, A.,Laureni, J.
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p. 486 - 496
(2007/10/02)
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