Catalyzed E/Z isomerization mechanism of stilbene using para-benzoquinone as a triplet sensitizer

2021 ◽  
Author(s):  
Kaho Nakatani ◽  
Hirofumi Sato ◽  
Ryoichi Fukuda
Keyword(s):  
Reaction Mechanism ◽  
Quantum Yield ◽  
Photochemical Reactions ◽  
Photochemical Processes ◽  
Isomerization Mechanism

Sensitizer molecules affect not only the quantum yield but also the selectivity of photochemical reactions. For an appropriate design of sensitized photochemical processes, we need to elucidate the reaction mechanism...

scholarly journals Imposed dynamic irradiation to intensify photocatalytic reactions

2021 ◽  
Author(s):  
Fabian Guba ◽  
Florian Gaulhofer ◽  
Dirk Ziegenbalg
Keyword(s):  
Large Scale ◽  
Reaction Rate ◽  
Photochemical Reactions ◽  
Test Reaction ◽  
Light Emitting ◽  
Photochemical Processes ◽  
Spatially Distributed ◽  
Photocatalytic Reactions ◽  
The Impact ◽  
Photonic Efficiency

AbstractDynamic irradiation is a potent option to influence the interaction between photochemical reactions and mass transport to design high performant and efficient photochemical processes. To systematically investigate the impact of this parameter, the photocatalytic reduction of nitrobenzene was conducted as a test reaction. Dynamic irradiation was realized through provoked secondary flow patterns, multiple spatially distributed light emitting diodes (LEDs) and electrical pulsation of LEDs. A combined experimental and theoretical approach revealed significant potential to enhance photochemical processes. The reaction rate was accelerated by more than 70% and even more important the photonic efficiency was increased by more than a factor of 4. This renders imposed dynamic irradiation an innovative and powerful tool to intensify photoreactions on the avenue to large scale sustainable photochemical processes.

The Charge Transfer Photochemistry of the Hexaaquoiron(III) Ion, the Chloropentaaquoiron(III) Ion, and the µ-Dihydroxo Dimer Explored with tert-Butyl Alcohol Scavenging

1975 ◽  
Vol 53 (16) ◽  
pp. 2430-2435 ◽  
Author(s):  
Cooper H. Langford ◽  
John H. Carey
Keyword(s):  
Charge Transfer ◽  
Quantum Yield ◽  
Butyl Alcohol ◽  
Extinction Coefficients ◽  
Photochemical Processes ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Radical Yield

There have been several studies of the charge transfer photochemistry of aqueous Fe3+ but the complexity of hydrolytic equilibria and the requirement for scavengers to render the primary photochemical processes observable has left several issues moot as recent reports show. Using tert-butyl alcohol as a scavenger, it is shown that (at 35 °C), charge transfer irradiation at 254 nm of Fe(OH2)63+ gives free •OH with a quantum yield of 0.065, charge transfer irradiation of Fe(OH2)5Cl2+ at 350 nm gives free Cl• with a quantum yield of 0.093, and that as a result of the combined patterns of extinction coefficients and hydrolytic equilibria it is difficult to make Fe(OH2)5OH + the main absorbing species at either wavelength. The dihydroxo-bridged dimer gives only a small radical yield. The scavenger, tert-butyl alcohol, appears to react with •OH or Cl• to give •CH2—C(CH3)2OH which, on reaction with a second Fe(OH2)63+ gives HOCH2C(CH3)2OH.

Photochemical processes of benzyltrimethylsilane at 77 K remarkable solvent effects and reaction mechanism

1996 ◽  
Vol 92 (17) ◽  
pp. 3035 ◽  
Author(s):  
Hiroshi Hiratsuka ◽  
Yukihiro Kadokura ◽  
Hiroyuki Chida ◽  
Mi�ko Tanaka ◽  
Satoshi Kobayashi ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Solvent Effects ◽  
Photochemical Processes

Spectral Dependencies of the Quantum Yield of Photochemical Processes on the Surface of Wide Band Gap Solids. 3. Gas/Solid Systems†

2000 ◽  
Vol 104 (14) ◽  
pp. 2989-2999 ◽  
Author(s):  
A. V. Emeline ◽  
G. N. Kuzmin ◽  
D. Purevdorj ◽  
V. K. Ryabchuk ◽  
N. Serpone
Keyword(s):  
Quantum Yield ◽  
Band Gap ◽  
Wide Band ◽  
Wide Band Gap ◽  
Photochemical Processes

The UV Photolysis (λ = 185 nm) of Liquid Methyl n-Propyl Ether

1975 ◽  
Vol 30 (5-6) ◽  
pp. 399-403 ◽  
Author(s):  
Heinz-Peter Schuchmann ◽  
Clemens von Sonntag
Keyword(s):  
Quantum Yield ◽  
Methyl Ether ◽  
Quantum Yields ◽  
Uv Photolysis ◽  
Photochemical Processes ◽  
Butyl Methyl Ether ◽  
Bond Splitting

The main products of the 185 nm photolysis of liquid methyl n-propyl ether (quantum yields in parentheses) are n-propanol (0.70), methane (0.29), sec-butyl methyl ether (0.20), methanol (0.16), propionaldehyde (0.13), 3,4-dimethoxyhexane (0.09), ethane (0.08), and ethyl n-propyl ether (0.08). The quantum yields of further 24 minor products have been measured. The quantum yield of the sum of primary photochemical processes, the main ones of which are the homolytic scissions of the C–O bonds (reactions i and ii), is close to unity.Reaction (i) is favoured over reaction (ii) by nearly a factor of five. The elimination of molecular methane (iii) is the only other process of importance. C–H and C–C bond splitting is marginal.

Der Einfluß der Bandbreite des Anregungslichtes bei der Bestimmung von Quantenausbeuten photochemischer Reaktionen / The Influence of the Bandwidth of the Exciting Light in Determining the Quantum Yields of Photochemical Reactions

1979 ◽  
Vol 34 (11) ◽  
pp. 1344-1351
Author(s):  
R. Schöneich ◽  
J. Bendig ◽  
D. Kreysig
Keyword(s):  
Quantum Yield ◽  
Radiation Intensity ◽  
Photochemical Reactions ◽  
Wave Number ◽  
Quantum Yields ◽  
Exciting Light ◽  
Considerable Influence ◽  
Interference Filters

Monochromatic excitation is one of the experimental requirements for determining quantum yields of photochemical reactions. It can, however, be strictly satisfied only in certain conditions. The photoisomerization of E,E-1,4-diphenylbutadiene-(1,3) is taken as an example for studying the effect of the bandwidth of the exciting light by using interference filters. The bandwidth is shown to have a considerable influence on the experimentally determined value of the partial quantum yield. Identical results are obtained when making allowance for the wave number dependence on radiation intensity and the absorption of the reactant compounds

Kinetics of the photochemical reactions of the croconate dianion in aqueous solution

1992 ◽  
Vol 70 (1) ◽  
pp. 135-143 ◽  
Author(s):  
B Zhao ◽  
M. H. Back
Keyword(s):  
Aqueous Solution ◽  
Electron Transfer ◽  
Quantum Yield ◽  
Rate Constants ◽  
Photochemical Reactions ◽  
Electron Acceptors ◽  
Basic Solution ◽  
Hydroxyl Ion ◽  
Kinetics Of

The kinetics of the photochemical reactions of the dianion of croconic acid (1,2-dihydroxycyclopentenetrione) have been studied in aqueous solution in the presence of electron acceptors. In neutral solutions the quantum yield for disappearance of croconate dianion was small (< 10−3) but was substantially increased in basic solution and in the presence of electron acceptors. At pH 12 in the presence of 4-nitrobenzylbromide and biacetyl a quantum yield of 1 was obtained. The kinetics of the rate of disappearance of croconate dianion as a function of pH and concentration of acceptor showed that the excited dianion is oxidized by acceptors and reacts with hydroxyl ion. A mechanism is proposed that, by assuming reasonable values for the rate constants involved, is shown to be consistent with the results. Keywords: photolysis, kinetics, croconate dianion, electron transfer.

The Reaction of O(3P) with C2Cl4

1974 ◽  
Vol 52 (23) ◽  
pp. 3870-3878 ◽  
Author(s):  
Eugenio Sanhueza ◽  
Julian Heicklen
Keyword(s):  
Reaction Mechanism ◽  
Quantum Yield ◽  
Chain Length ◽  
Rate Coefficient ◽  
Chain Process ◽  
Reaction Conditions ◽  
Text Production ◽  
Competitive Kinetics ◽  
A Chain ◽  
Cl Atom

The reaction of O(3P), prepared from Hg photosensitization of N2O with C2Cl4 was studied at 25 °C. The exclusive products of the reaction in the absence of O2 were CCl2O and polymer (as well as N2 from the N2O). The quantum yield of CCl2O production, Φ{CCl2O}, was 0.19 independent of the C2Cl4 pressure or the absorbed intensity, Ia. There was no evidence for CO, Cl2, c-C3Cl6, CCl3CCl(O), or [Formula: see text] production. The reaction mechanism is[Formula: see text]with k12a/k12 = 0.19. The CCl2 radical dimerizes and the energetic C2Cl4O* intermediate polymerizes. By competitive kinetics, the ratio k12/k13 was found to be 0.10, where k12 ≡ k12a + k12b and k13 is the rate coefficient of the O(3P) + C2F4 reaction.In the presence of O2, a chain process is involved in which CCl3CCl(O) and CCl2O are the major products. They are formed in a ratio of 2.0 independent of reaction conditions, but the chain length is proportional to [C2Cl4]/Ia1/2. Also produced is CO with a quantum yield of ∼0.18. The ratio Φ{CCl3CCl(O)}/Φ{CCl2O} = 2.0 is similar to that of 2.5 found in the Cl atom initiated oxidation. This result is interpreted to mean that chlorine atoms are involved in the chain. The reaction which initiates monoradicals in the system is[Formula: see text]

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