18282-77-4Relevant academic research and scientific papers
Direct identification of photofragment structures formed in the 193 nm photodissociation of thiophene
Hsu,Liao,Ma,Ng
, p. 1760 - 1767 (1995)
An experimental scheme which involves vacuum ultraviolet photoionization mass spectrometric sampling of laser photodissociation products in a pulsed supersonic molecular beam has been used to identify the isomeric structures of the 193 nm photofragments from thiophene. The primary products observed are vinylacetylene (H2C=CH-C≡CH), acetylene (C2H2), and thioketene (H2C=C=S). Using the 2 + 1 resonance-enhanced multiphoton (REMPI) scheme, we find that S atoms are produced predominantly (≥96%) in 3PJ states with a fine structure distribution of 3P2:3P1:3P0 = 0.82 ± 0.03:0.15 ± 0.03:0.03 ± 0.03. These experimental results indicate that the major dissociation channels are CH2=CH-C≡CH + S(3P) and CH=CH + CH2=C=S. Ab initio multiconfiguration self-consistent-field calculations have been made to rationalize these experimental observations.
Formation of thiophenethiols by flash vacuum pyrolysis of 1,6,6aλ4-trithiapentalenes
Flammang, Robert,Barbieux-Flammang, Monique,Gerbaux, Pascal,Pedersen, Carl Th.
, p. 1261 - 1264 (2007/10/03)
The thermal behaviour of 1,6,6aλ4-trithiapentalene 3 and some methyl-substituted derivatives 5-7 has been investigated using a combination of flash vacuum pyrolysis (FVP), tandem mass spectrometry (MS-MS) and matrix isolation IR spectroscopy. the main products of the fragmentation (losses of CS and/or CH2=C=S) are shown to be thiophene-3-thiones (or the thiol tautomers) which are also shown to be readily available by direct sulfuration of thiophenes in chemical ionization (CS2 reagent gas) conditions.
HCl Elimination from Ethanesulfenyl Chloride and Chlorodimethyl Sulfide
Maier, Guenther,Floegel, Ulrich,Reisenauer, Hans Peter,Hess, B. Andes,Schaad, Lawrence J.
, p. 2609 - 2612 (2007/10/02)
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
A Gas-phase Anionic Analog of the Wittig Reaction. An Ion Cyclotron Resonance Study of the Gas-phase Ion Chemistry of Silyl Carbanions
Campanaro, A.,Marvin, C. H.,Morehouse, S. P.,McMahon, T. B.
, p. 663 - 668 (2007/10/02)
Gas-phase ion-molecule reactions of a variety of fluorosilyl carbanions with compounds containing double bonds to oxygen, X=O, have been examined using pulsed ion cyclotron resonance spectroscopy.The predominant reaction channel observed for species not containing acidic hydrogen is a Wittig-like process involving Si-O bond formation and elimination of X=CH2 species.The gas-phase acidity of F3Si(CH3) has been determined and those of F2Si(CH3)2 and FSi(CH3)3 have been estimated.From the fluoride transfer reactions of F3SiCH2- the fluoride affinity of F2Si=CH2 has been estimated and limits on the ? bond strength in this silaethene obtained.Potential analytical applications of the Wittig reactivity have been discussed.
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
Hawkins, Michael,Almond, Matthew,Downs, Anthony J.
, p. 3326 - 3334 (2007/10/02)
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.
Reactions of Thiophene and Alkylthiophenes in Glow Discharge
Skramstad, Jan,Chaudhry, Mohammed Shoaib,Garvang, Arne
, p. 509 - 512 (2007/10/02)
The glow discharge reaction of thiophene is shown to produce thioketene and carbon monosulfide along with other gaseous products.The dominant liquid product is ethynylthiophene.Methylthiophenes and especially dimethylthiophenes produce benzene as one of the major liquid products.
Argon-Matrix Isolation of Bis(carbomethoxy)thiirene: Formation of Acyl and Carbalkoxythioketenes
Torres, M.,Clement, A.,Strausz, O. P.
, p. 1208 - 1212 (2007/10/02)
Photolysis of argon-matrix isolated 4,5-bis(carbomethoxy)-1,2,3-thiadiazole with λ=254 or 265 nm resulted in the almost quantitative formation of bis(carbomethoxy)-thiirene (3g).Photolysis of 3g could only be carried out by long irradiation times at short wavelength λ=210 nm and resulted mainly in extensive fragmentation instead of the formation of bis(carbomethoxy)thioketene, confirming earlier predictions that substituents, especially electron-withdrawing ones, should stabilize the thiirene ring.Methylcarboethoxy and methylacetylthioketene were obtained, however, in the argon-matrix photolysis or flow thermolysis of 4-methyl-5-carboethoxy- or 4-carboethoxy-5-methyl-1,2,3-thiadiazole and 4-acetyl-5-methyl-1,2,3-thiadiazole, respectively. - Key words: Thiirene, Thioketene, 1,2,3-Thiadiazole, Thio-Wolff Rearrangement
Gas Phase Reactions, 24. The Thermal Generation of Thiocarbonyl Compounds
Bock, Hans,Hirabayashi, Takakuni,Mohmand, Shamsher
, p. 492 - 503 (2007/10/02)
Thiocarbonyl derivatives R1R2C=S with R1, R2 = H, CH3, C6H5 can be generated thermally in the gas phase from a variety of precursors.Especially advantageous are the cleavage of propene from allyl sulfides or, for their preparation in pure form, the pyrolysis of dithietane or trithiolane derivatives.Photoelectron spectroscopy proves to be well-suited for gas analysis in the flow tube used, for the optimization of the decomposition conditions, and via assignment of the observed ionization patterns for the characterization of the thioaldehydes and thioketones prepared.
Characterization of Matrix-Isolated Antiaromatic Three-Membered Heterocycles. Preparation of the Elusive Thiirene Molecule
Krantz, A.,Laureni, J.
, p. 486 - 496 (2007/10/02)
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).
