Reactions of thiyl radicals. XII. Triplet mercury photosensitized decomposition of ethyl sulfide in the gas phase

1976 ◽  
Vol 54 (8) ◽  
pp. 1290-1295 ◽  
Author(s):  
Conrad S. Smith ◽  
Arthur R. Knight
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
Quantum Yields ◽  
Second Step ◽  
Primary Process ◽  
Reaction Products ◽  
Process Comparison ◽  
Thiyl Radicals ◽  
Ethyl Radicals ◽  
High Sulfide

The triplet mercury photosensitized decomposition of ethyl sulfide vapour has been studied at 25 °C. The reaction products include C2H4 (Φ0 = 0.075), C2H6 (Φ0 = 0.043), C4H10 (Φ0 = 0.011), C2H5SH (Φ0 = 0.068), 4-methyl-3-thiahexane (Φ0 = 0.011), and C2H5SSC2H5 (Φ0 = 0.175). The overall decomposition quantum yield is 0.38 at high sulfide pressures. The initial decomposition gives principally ethyl radicals and ethylthiyl radicals; a second step which yields ethylene and ethanethiol may account for up to 20% of the primary process. Comparison of the direct and sensitized decompositions indicates that both likely originate in the triplet manifold of ethyl sulfide.Primary decomposition quantum yields have been accurately redetermined for the direct, 254 nm, photolysis of methyl sulfide (0.51), methylethyl sulfide (0.46), and ethyl sulfide (0.49).

Excited radicals in the gas phase photolysis of butene isomers at different photon energies: energy distribution in reaction products

1978 ◽  
Vol 56 (20) ◽  
pp. 2630-2637 ◽  
Author(s):  
Guy J. Collin ◽  
Andrzej Więckowski
Keyword(s):  
Quantum Yield ◽  
Kinetic Energy ◽  
Energy Distribution ◽  
Gas Phase ◽  
Excess Energy ◽  
Pressure Effects ◽  
Quantum Yields ◽  
Reaction Products ◽  
Hydrogen Atoms ◽  
Pressure Region

A systematic study of the pressure effects on the quantum yields of some products between 0.1 and 600 Torr (13 and 80 000 N m−2) was carried out in the 7.6 and 8.4 eV photolysis of normal, iso- and cis-2-butenes. The propylene quantum yield (s-C4H9* → C3H6 + CH3) decreased with the increase in the n-butene pressure and a good linearity of S/D (stabilization/decomposition) vs. pressure plot, over a broad pressure region, was observed. It is concluded that hydrogen atoms involved in the s-C4H9* radical formation are produced with a relatively narrow energy distribution. The slope of S/D vs. pressure lines decreased with the increase in photon energy, indicating the trend in the kinetic energy of the H-atoms.In the case of isobutene and cis-2-butene photolysis, the Stern–Volmer plots for allene formation were nonlinear. It is concluded that the formation of two different allene precursors is needed to account for this result. By the use of a simple RRK-type formalism we also conclude that the excess energy of the photon in the primary photoexcited butene molecules is far from being randomized before their fragmentation occurs.[Formula: see text]

Reactions of Thiyl Radicals. X. Photolysis of Ethyl Sulfide Vapor

1973 ◽  
Vol 51 (5) ◽  
pp. 780-786 ◽  
Author(s):  
Conrad S. Smith ◽  
Arthur R. Knight
Keyword(s):  
Reaction Rates ◽  
Quantum Yields ◽  
Minor Role ◽  
Primary Decomposition ◽  
Primary Process ◽  
Temperature Reaction ◽  
Reaction Products ◽  
Thiyl Radicals ◽  
Pressure Time ◽  
A Minor

The photolysis of ethyl sulfide vapor at 2537 Å has been investigated as a function of substrate and CF4 pressure, time, and temperature. Reaction products with quantum yields in parentheses are ethyl disulfide (0.178), ethane (0.138), butane (0.086), ethanethiol (0.096), 4-methyl-3-thiahexane (0.034) and 4-methyl-3,5-dithiaheptane.Ethyl and ethylthiyl radicals are formed in the primary process and the product yields indicate a net primary decomposition quantum yield of 0.48. A reaction mechanism involving subsequent reactions of the primary fragments is proposed and explains the observed products and the observed variation in rates. Excited radicals and hot radical combination products play a minor role in this system, in contrast to the behavior of lower molecular weight sulfides. Secondary photolysis of the disulfide produced and consumption of ethanethiol are important factors in determining the time dependence of reaction rates in this system.

The photolysis of 2,3- and 3,3-dimethyl-1-butene at 147.0 and 184.9 nm

1985 ◽  
Vol 63 (1) ◽  
pp. 62-67 ◽  
Author(s):  
Hélène Deslauriers ◽  
Guy J. Collin
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
Electronic State ◽  
Photon Energy ◽  
Low Pressure ◽  
Decomposition Process ◽  
Primary Decomposition ◽  
Primary Process ◽  
The One

The photofragmentation of 2,3-dimethylbutene and 3,3-dimethylbutene has been studied at 147 and 184.9 nm in the gas phase. The main primary decomposition process at both wavelengths involves the rupture of a β(C—C) bond. The quantum yield for this process is higher than 0.7 at 147 nm and is probably even higher at 184.9 nm. All dimethallyl radicals formed at 147 nm in this process decompose at low pressure, but some of them isomerize from the α,β- to the α,α- structure (and vice versa) — via a 1,4-H transfer — before decomposition. At 184.9 nm, the same primary process is used to get a rough value for the lifetime of the photoexcited molecule, compared with the one made with RRKM calculations by assuming that all the photon energy resides in the vibrational framework of the fundamental electronic state. These lifetimes are about one nanosecond or less.

THE Hg 6(3P1) PHOTOSENSITIZATION OF CHLORODIFLUOROMETHANE

1965 ◽  
Vol 43 (5) ◽  
pp. 1022-1029 ◽  
Author(s):  
M. G. Bellas ◽  
O. P. Strausz ◽  
H. E. Gunning
Keyword(s):  
Incident Light ◽  
Strong Dependence ◽  
Quantum Yields ◽  
Primary Process ◽  
Reaction Products ◽  
Light Intensities ◽  
Principal Reaction ◽  
Bond Scission ◽  
Circulatory Apparatus ◽  
Cl Atoms

The reaction was studied in a circulatory apparatus under a variety of conditions. The sole primary process occurring is C—Cl bond scission. The Cl atoms formed in the primary step, through an abstractive attack on the substrate, generate chlorodifluoromethyl radicals (CF2Cl) All principal reaction products, CF2H2, CF2Cl2, CF2ClCF2Cl, CF2HCF2H, and CF2HCF2Cl, can be accounted for by the combination–disproportionation reactions of the CF2H• and CF2Cl• radicals. The observed strong dependence of the primary quantum yields on the incident light intensities has been ascribed to a rapid substrate-reforming step.

Reactions of Thiyl Radicals. VII. Photolysis of Methyl Sulfide Vapor

1972 ◽  
Vol 50 (6) ◽  
pp. 844-852 ◽  
Author(s):  
P. M. Rao ◽  
A. R. Knight
Keyword(s):  
Wavelength Range ◽  
Sulfur Hexafluoride ◽  
Quantum Yields ◽  
Primary Process ◽  
Methyl Radicals ◽  
Methyl Sulfide ◽  
Thiyl Radicals ◽  
Several Variables ◽  
Bond Scission ◽  
Function Of Several Variables

The photolysis of methyl sulfide vapor has been investigated as a function of substrate pressure, exposure time, and temperature in the wavelength range 2000 to 2300 Å. The effects of added propane, sulfur hexafluoride, and 2-methylpentane have been studied. The principal products of the decomposition are CH4, C2H6, CH3SSCH3, and CH3SH. The data indicate direct C—S bond scission in the primary process giving rise to "hot" CH3 and CH3S radicals. A mechanism in which disproportionation of methylthiyl radicals is a very minor process is proposed.The reactions of CH3 and CH3S radicals with methyl sulfide have been examined also by photolyzing CH3SSCH3 and CH3COCH3 in the presence of CH3SCH3. Quantum yields at 2288 Å have been determined as a function of several variables. A number of rate parameters for the reactions of methyl radicals and methylthiyl radicals have been calculated.

The photolysis of tetrahydrofuran and of some of its methyl derivatives at 185 nm

1980 ◽  
Vol 58 (24) ◽  
pp. 2819-2826 ◽  
Author(s):  
Nuray Klzilkilic ◽  
Heinz-Peter Schuchmann ◽  
Clemens von Sonntag
Keyword(s):  
Liquid Phase ◽  
Quantum Yield ◽  
Gas Phase ◽  
Carbonyl Compounds ◽  
Quantum Yields ◽  
Product Analysis ◽  
A Value ◽  
Steric Factors ◽  
Methyl Derivatives ◽  
Group 1

The uv photolysis of tetrahydrofuran, 1, 2-methyltetrahydrofuran, 2, cis-2,5-dimethyltetrahydrofuran, 3, trans-2,5-dimethyltetrahydrofuran, 4, and 2,2,5,5-tetramethyltetrahydrofuran, 5, has been investigated by product analysis in the liquid phase, and quantum yields have been determined. The photolysis of tetrahydrofuran itself was also studied in the gas phase at pressures ranging from 1 to 120 atm (pressurizing gas N2); and very little difference was found between the photolytic behaviour of the vapour at 120 atm and that of the liquid. The major products are in ail cases the cyclopropanes and the corresponding carbonyl compounds, as well as the olefinic alcohols and the carbonyl compounds that are isomeric with the starting material. These products are considered to be formed by the two major primary processes [i] and [ii].[Formula: see text]The cyclopropanes formed in reaction [i] retain some excess energy (apparently more than is needed to realize the trimethylene form), and in the photolysis of tetrahydrofuran vapour the hot cyclopropane rearranges to a considerable extent into propene. The propene to cyclopropane yield ratio falls strongly with increasing pressure, to a value of 0.065 at 120 atm. A similar value is observed in the liquid phase photolysis.The five-membered oxyl alkyl diradical from reaction [ii] is the likely intermediate in the cis-trans photoisomerization that is observable with the 2,5-dimethyltetrahydrofurans [Formula: see text]. The photolysis of these compounds also demonstrates that steric factors have a strong bearing on the course of the reaction, e.g. the quantum yield of methylcyclopropane from the cis compound is 0.22, vs. 0.08 from the trans compound.Molecular hydrogen is produced if the tetrahydrofurans carry hydrogen in α-position. Its production is enhanced if the α-position is shared with a methyl group (1 gives a hydrogen quantum yield of 0.07, 2 of 0.17, 3 of 0.27, 4 of 0.29, and 5 of zero).

COMPUTER MODELING OF CHEMICAL EQUILIBRIUMS IN WO3–H2O SYSTEM

2017 ◽  
pp. 35-48 ◽  
Author(s):  
V.P. Bondarenko ◽  
O.O. Matviichuk
Keyword(s):  
Transition Temperature ◽  
Gas Phase ◽  
Single Phase ◽  
Reference Data ◽  
Maximum Amount ◽  
Reaction Products ◽  
Influence Of Temperature ◽  
Equilibrium Chemical ◽  
Program Data ◽  
Good Agreement

Detail investigation of equilibrium chemical reactions in WO3–H2O system using computer program FacktSage with the aim to establish influence of temperature and quantity of water on formation of compounds of H2WO4 and WO2(OH)2 as well as concomitant them compounds, evaporation products, decomposition and dissociation, that are contained in the program data base were carried out. Calculations in the temperature range from 100 to 3000 °С were carried out. The amount moles of water added to 1 mole of WO3 was varied from 0 to 27. It is found that the obtained data by the melting and evaporation temperatures of single-phase WO3 are in good agreement with the reference data and provide additionally detailed information on the composition of the gas phase. It was shown that under heating of 1 mole single-phase WO3 up to 3000 °С the predominant oxide that exist in gaseous phase is (WO3)2. Reactions of it formation from other oxides ((WO3)3 and (WO3)4) were proposed. It was established that compound H2WO4 is stable and it is decomposed on WO3 and H2O under 121 °C. Tungsten Oxide Hydrate WO2(OH)2 first appears under 400 °С and exists up to 3000 °С. Increasing quantity of Н2О in system leads to decreasing transition temperature of WO3 into both liquid and gaseous phases. It was established that adding to 1 mole WO3 26 mole H2O maximum amount (0,9044–0,9171 mole) WO2(OH)2 under temperatures 1400–1600 °С can be obtained, wherein the melting stage of WO3 is omitted. Obtained data also allowed to state that that from 121 till 400 °С WO3–Н2O the section in the О–W–H ternary system is partially quasi-binary because under these temperatures in the system only WO3 and Н2O are present. Under higher temperatures WO3–Н2O section becomes not quasi-binary since in the reaction products WO3 with Н2O except WO3 and Н2O, there are significant amounts of WO2(OH)2, (WO3)2, (WO3)3, (WO3)4 and a small amount of atoms and other compounds. Bibl. 12, Fig. 6, Tab. 5.

scholarly journals Ruthenium-based PACT agents based on bisquinoline chelates: synthesis, photochemistry, and cytotoxicity

2021 ◽  
Author(s):  
Anja Busemann ◽  
Ingrid Flaspohler ◽  
Xue-Quan Zhou ◽  
Claudia Schmidt ◽  
Sina K. Goetzfried ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Singlet Oxygen ◽  
Cancer Cells ◽  
Cellular Uptake ◽  
Ruthenium Complex ◽  
Human Cancer ◽  
Light Irradiation ◽  
Quantum Yields ◽  
Light Activation ◽  
Human Cancer Cells

AbstractThe known ruthenium complex [Ru(tpy)(bpy)(Hmte)](PF6)2 ([1](PF6)2, where tpy = 2,2’:6’,2″-terpyridine, bpy = 2,2’-bipyridine, Hmte = 2-(methylthio)ethanol) is photosubstitutionally active but non-toxic to cancer cells even upon light irradiation. In this work, the two analogs complexes [Ru(tpy)(NN)(Hmte)](PF6)2, where NN = 3,3'-biisoquinoline (i-biq, [2](PF6)2) and di(isoquinolin-3-yl)amine (i-Hdiqa, [3](PF6)2), were synthesized and their photochemistry and phototoxicity evaluated to assess their suitability as photoactivated chemotherapy (PACT) agents. The increase of the aromatic surface of [2](PF6)2 and [3](PF6)2, compared to [1](PF6)2, leads to higher lipophilicity and higher cellular uptake for the former complexes. Such improved uptake is directly correlated to the cytotoxicity of these compounds in the dark: while [2](PF6)2 and [3](PF6)2 showed low EC50 values in human cancer cells, [1](PF6)2 is not cytotoxic due to poor cellular uptake. While stable in the dark, all complexes substituted the protecting thioether ligand upon light irradiation (520 nm), with the highest photosubstitution quantum yield found for [3](PF6)2 (Φ[3] = 0.070). Compounds [2](PF6)2 and [3](PF6)2 were found both more cytotoxic after light activation than in the dark, with a photo index of 4. Considering the very low singlet oxygen quantum yields of these compounds, and the lack of cytotoxicity of the photoreleased Hmte thioether ligand, it can be concluded that the toxicity observed after light activation is due to the photoreleased aqua complexes [Ru(tpy)(NN)(OH2)]2+, and thus that [2](PF6)2 and [3](PF6)2 are promising PACT candidates. Graphic abstract

High Quantum Yield Dual Emission from Gas-Phase Grown Crystalline Si Nanoparticles

2014 ◽  
Vol 118 (19) ◽  
pp. 10375-10383 ◽  
Author(s):  
A. M. P. Botas ◽  
R. A. S. Ferreira ◽  
R. N. Pereira ◽  
R. J. Anthony ◽  
T. Moura ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
High Quantum Yield ◽  
Dual Emission ◽  
High Quantum ◽  
Si Nanoparticles

Quantum yield of solution photolysis of bicyclo[3.1.0]hexan-3-one and derivatives

1981 ◽  
Vol 59 (11) ◽  
pp. 1607-1609 ◽  
Author(s):  
Karl R. Kopecky ◽  
Rodrigo Rico Gomez
Keyword(s):  
Quantum Yield ◽  
Quantum Yields

The quantum yields for photolysis of 0.25 M solutions of bicyclo[3.1.0]hexan-3-one, 1,5-dimethylbicyclo[3.1.0]hexan-3-one, and tricyclo[4.3.1.0]decan-8-one in pentane or cyclohexane with 313 nm light are 0.44, 0.52, and 0.32, respectively.

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