The photochemistry of aqueous solutions of Tl(III) perchlorate

1970 ◽  
Vol 48 (19) ◽  
pp. 2955-2959 ◽  
Author(s):  
C. E. Burchill ◽  
W. H. Wolodarsky
Keyword(s):  
Charge Transfer ◽  
Quantum Yield ◽  
Flash Photolysis ◽  
Primary Process ◽  
Chain Reaction ◽  
Perchloric Acid Solution ◽  
Upper Limit ◽  
Aqueous Perchloric Acid ◽  
A Chain ◽  
A Charge

In deaerated aqueous perchloric acid solution Tl(III) is reduced and 2-propanol oxidized to acetone in equivalent yields via a chain reaction initiated by light of 2537 Å. Initiation is attributed to a charge-transfer-to-metal excitation followed by dissociation[Formula: see text]The formation of Tl(II) in the primary process is demonstrated by flash photolysis. An upper limit of 0.36 ± 0.07 is estimated for the primary quantum yield.

KINETICS OF THE OXIDATION OF URANIUM(IV) BY MOLECULAR OXYGEN IN AQUEOUS PERCHLORIC ACID SOLUTION

1956 ◽  
Vol 34 (10) ◽  
pp. 1419-1427 ◽  
Author(s):  
J. Halpern ◽  
J. G. Smith
Keyword(s):  
Reaction Mechanism ◽  
Acid Solution ◽  
Molecular Oxygen ◽  
Perchloric Acid ◽  
Chain Reaction ◽  
Perchloric Acid Solution ◽  
Aqueous Perchloric Acid ◽  
A Chain ◽  
Kinetics Of ◽  
Considerable Range

The kinetics of the oxidation of uranium(IV) by molecular oxygen in aqueous perchloric acid solution were studied. Over a considerable range of conditions, the results are fitted approximately by the rate law:−d[UIV]/dt = k[UIV] [O2]/[H+], where k ≈ 2 × 1014 exp[−22,000/RT]sec.−1. The reaction is catalyzed by Cu++ and inhibited by small amounts of Ag+ and Cl−. The results are interpreted in terms of a chain reaction mechanism involving UO2+ and HO2 as chain carriers.

Hydrogen vs. electron transfer mechanisms in the chain decomposition of phenacyl bromides. Use of isotopic labeling as a mechanistic probe

1996 ◽  
Vol 74 (9) ◽  
pp. 1724-1730 ◽  
Author(s):  
Jocelyn Renaud ◽  
J. C. Scaiano
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Key Words ◽  
Hydrogen Transfer ◽  
Isotopic Labeling ◽  
Chain Reaction ◽  
Phenacyl Bromides ◽  
Mechanistic Probe ◽  
A Chain ◽  
Transfer Mechanisms

Ring-substituted α-bromoacetophenones react with alcohols in a chain reaction leading to the corresponding acetophenone, HBr, and the carbonyl compound from oxidation of the alcohol. Two different mechanisms, involving hydrogen or electron transfer by ketyl radicals, have been proposed in order to accommodate the unusual selectivities of these reactions. By studying the efficiency of isotope incorporation from deuterated alcohols, it has been possible to determine the relative contributions from both mechanisms. For example, electron transfer dominates in the case of 2-propanol, while hydrogen transfer is more important for methanol. The results demonstrate that ring substitution in the starting ketone is not a main contributing factor in the discrimination between the two mechanisms. The only parameter that seems to be playing a major role is the nature (reducing strength) of the ketyl radicals. Key words: dehydrobromination, charge transfer, isotope effect, ketyl radicals.

Triplet energies of fumaronitrile and maleonitrile

1982 ◽  
Vol 60 (3) ◽  
pp. 339-341 ◽  
Author(s):  
Po Cheong Wong
Keyword(s):  
Charge Transfer ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Benzene Solution ◽  
Laser Flash ◽  
Transfer Mechanism ◽  
Triplet Energy ◽  
Charge Transfer Mechanism ◽  
A Charge

The triplet energies of fumaronitrile and maleonitrile measured by laser flash photolysis technique using the Herkstroeter–Hammond method are both 59 ± 2 kcal mol−1. Our results show that these olefins are classical triplet energy acceptors for non-electron donating sensitizers. With electron donating sensitizers, quenching through a charge-transfer mechanism also occurs in benzene solution.

Hydrated Electrons Formed in the Flash Photolysis of Ag° and Tl°

1973 ◽  
Vol 51 (15) ◽  
pp. 2497-2501 ◽  
Author(s):  
Norman Basco ◽  
Sunil K. Vidyarthi ◽  
David C. Walker
Keyword(s):  
Charge Transfer ◽  
Absorption Band ◽  
Work Function ◽  
Wavelength Range ◽  
Flash Photolysis ◽  
Transient Species ◽  
Hydrated Electrons ◽  
A Charge ◽  
Silver Metal ◽  
Double Flash

The transient species Ag0, formed in the reduction of Ag+ by hydrated electrons, may be photodissociated to eaq− again by light in the absorption band of Ag0 centered at ~315 nm.[Formula: see text]It suggests that this band is a charge-transfer-to-solvent band. The photon energy threshold for photoionization of Ag0 (3.0 eV) is substantially smaller than the vacuum photoelectric work function of silver metal (4.5 eV). Analogous results were obtained in solutions of Tl+ indicating that Tl0 may also yield eaq− on photolysis at ~300 nm. The experiments utilized a double flash photolysis technique, in which hydrated electrons were produced by u.v. photolysis of SO42− in the first flash, reacted with Ag+ or Tl+ to give the short-lived intermediates Ag0 (lifetime ~60 μs) and T10 (lifetime < 20 μs) which were photolyzed by a second flash containing light in a restricted wavelength range.

Radiation-induced oxidation of alcohols by TI(III) in acid aqueous solution

1970 ◽  
Vol 48 (16) ◽  
pp. 2466-2473 ◽  
Author(s):  
C. E. Burchill ◽  
G. G. Hickling
Keyword(s):  
Butyl Alcohol ◽  
Alcohol Concentration ◽  
Lower Yield ◽  
Chain Reaction ◽  
Perchloric Acid Solution ◽  
Oxidation Of Alcohols ◽  
Radiation Induced ◽  
Acid Aqueous Solution ◽  
Aqueous Perchloric Acid ◽  
Γ Ray

In deaerated aqueous perchloric acid solution TI(III) is reduced and 2-propanol oxidized to acetone in essentially equivalent yields by a γ-ray induced chain reaction. The yields increase linearly with increasing alcohol concentration in the range (1–8) × 10−2 M, are independent of TI(III) concentration in the range (1–4) × 10−3 M and vary inversely with the square root of the dose rate over the range 1.6 × 1017 to 1.8 × 1019 eV l−1 s−1. A mechanism is proposed to account for the observed stoichiometry and kinetic parameters.The same mechanism is found to apply to the reduction of TI(III) by methanol and ethanol. t-Butyl alcohol gives a much lower yield of TI(III) reduction and alcohol fragmentation products: acetone, methane, and ethane.

Die Kinetik und der Mechanismus der thermischen Reaktion zwischen Schwefeltetrafluorid und Fluor / The Kinetics and the Mechanism of the Thermal Reaction between Sulfurtetrafluoride and Fluorine

1981 ◽  
Vol 36 (11) ◽  
pp. 1381-1385 ◽  
Author(s):  
Alicia Cristina Gonzalez ◽  
Hans Joachim Schumacher
Keyword(s):  
Chain Length ◽  
Total Pressure ◽  
Reaction Rate ◽  
Thermal Reaction ◽  
Primary Process ◽  
Chain Reaction ◽  
Experimental Conditions ◽  
Medium Length ◽  
A Chain ◽  
Kinetics Of

AbstractThe kinetics of the thermal reaction between SF4 and F2 has been investigated between − 2.4 °C and + 24.0 °C, SF6 and very small amounts of S2F10 being the only products. The reaction is a chain reaction of medium length. Total pressure and surface have only insignificant influence. The reaction rate follows the equation: Under the experimental conditions less than 15% of the SF5 radicals are consumed by r (4b). Therefore Oxygen inhibits the reaction eliminating the SF5 radicals, the final products being now SF5O3SF5 and SF6. From the data obtained in the experiments with high oxygen pressures the rate constant of the primary process and the chain length (v) are determined. E = 10.8 ± 0.7 kcal, E1 = 11.9 ± 0.6 kcal and E4 ≃ 0. E2 = 5.0 ± 2.0 kcal (estimated value) and E3 = 4.7 ± 2.5 kcal.

The photolysis of ozone by ultraviolet radiation. II. The photolysis of ozone mixed with certain hydrogen-containing substances

1965 ◽  
Vol 288 (1414) ◽  
pp. 361-370 ◽  
Keyword(s):  
Quantum Yield ◽  
Ultraviolet Radiation ◽  
Hydroxyl Radical ◽  
Hydrogen Chloride ◽  
Water Vapour ◽  
Kinetic Scheme ◽  
Chain Reaction ◽  
Secondary Reactions ◽  
A Chain ◽  
Experimental Findings

The quantum yield of the photolysis of ozone at λ = 2537 Å has been determined in the presence of water vapour, hydrogen, methane, hydrogen chloride and ammonia. In each case, the quantum yield determined was greater than that for pure ozone, and it is suggested that 1 D oxygen atoms formed in the primary photolytic step are able to react with the added gas to form a hydroxyl radical which is then able to propagate a chain reaction. A general kinetic scheme, consistent with the experimental findings, is presented, and the secondary reactions in the several cases are discussed.

scholarly journals The combination of hydrogen and oxygen on the surface of silica and its relation to the propagation of reaction chains in the gas

1931 ◽  
Vol 134 (823) ◽  
pp. 1-7 ◽  
Keyword(s):  
Gas Phase ◽  
Surface Reaction ◽  
Silica Surface ◽  
Chain Reaction ◽  
First Order ◽  
Slow Reaction ◽  
Upper Limit ◽  
A Chain ◽  
Reaction Vessels

The combination of hydrogen and oxygen, at temperatures between 400° and 600°C. in vessels of porcelain or silica involves several different processes. At the lower temperatures a surface reaction tends to predominate, which on a silica surface is approximately of the first order. At higher temperatures and higher pressures a chain reaction occurs in the gas phase. At temperatures greater than 450° C. there also exists a lower and an upper limit of pressure below and above which reaction is slow and between which explosion occurs.The transition from slow reaction to explosion is an abrupt one, the limits representing discontinuities of some kind. The upper limit is almost the same in reaction vessels of silica or porcelain and is nearly independent of their dimensions.

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