Flash photolysis of phenylacetatopentaminecobalt(III) in aqueous solution. Generation of benzyl radicals and their reversible trapping by cupric ions in homogeneous and micellar solutions

1984 ◽  
Vol 62 (11) ◽  
pp. 2355-2358 ◽  
Author(s):  
J. C. Scaiano ◽  
W. J. Leigh ◽  
G. Ferraudi
Keyword(s):  
Aqueous Solution ◽  
Rate Constant ◽  
Flash Photolysis ◽  
Micellar Solutions ◽  
Aqueous Systems ◽  
Solution Generation ◽  
Benzyl Radicals ◽  
Anionic Micelles ◽  
Decay Path

The photodecomposition of [Co(NH3)5OC(O)CH2C6H5](ClO4)2 is a convenient source of benzyl radicals in aqueous systems. The radicals react with cupric ions with a rate constant of (2.1 ± 0.2) × 107 M−1 s−1 to yield a complex that is formed reversibly. This complex can decay to Cu(I), but at high radical concentrations the recombination of benzyl radicals in equilibrium with it can become the predominant decay path. The reaction of benzyl radicals (from 1,3-diphenylacetone) in anionic micelles in the presence of Cu2+ leads to strong signals from the same intermediate, CuCH2C6H52+.

The 2-oxo-3,3,5,5-tetramethylcyclopentanecarboxylic acid keto–enol system in aqueous solution — Generation of the enol by flash photolytic Wolff rearrangement of 2-diazo-4,4,6,6-tetramethylcyclohexane-1,3-dione followed by hydration of the acylketene thus formed

2005 ◽  
Vol 83 (1) ◽  
pp. 68-76 ◽  
Author(s):  
Y Chiang ◽  
A J Kresge ◽  
V A Nikolaev ◽  
I Onyido ◽  
X Zeng
Keyword(s):  
Aqueous Solution ◽  
Sodium Hydroxide ◽  
Equilibrium Constant ◽  
Perchloric Acid ◽  
Flash Photolysis ◽  
Keto Form ◽  
Wolff Rearrangement ◽  
Buffer Solutions ◽  
Solution Generation ◽  
Oxocarboxylic Acids

Flash photolysis of 2-diazo-4,4,6,6-tetramethylcyclohexane-1,3-dione in aqueous solution produced 2-oxo-3,3,5,5-tetramethylcyclopentylideneketene, which underwent hydration to the enol of 2-oxo-3,3,5,5-tetramethylcyclo pentanecarboxylic acid; the enol then isomerized to the keto form of the acid. Rates of hydration of the ketene and rates of ketonization of the enol were measured in perchloric acid, sodium hydroxide, and buffer solutions, and rate profiles were constructed. Rates of enolization of 2-oxo-3,3,5,5-tetramethylcyclopentanecarboyxlic acid were also measured, using bromine to scavenge the enol as it formed, and rates of enolization and ketonization were then combined to give the keto–enol equilibrium constant pKE = 1.65. This and other results are discussed in comparison with the behavior of the unmethylated 2-oxocyclopentanecarboxylic acid system.Key words: flash photolysis, photo-Wolff reaction, ketene hydration, enolization, ketonization, keto–enol equilibria, β-oxocarboxylic acids.

Flash photolysis and pulse radiolysis of the Co(sep)3+-X- (sep = sepulchrate; X = I, Br) systems in aqueous solution

1986 ◽  
Vol 25 (23) ◽  
pp. 4249-4252 ◽  
Author(s):  
Fernando Pina ◽  
Mauro Maestri ◽  
Roberto Ballardini ◽  
Quinto G. Mulazzani ◽  
Mila D'Angelantonio ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Pulse Radiolysis ◽  
Flash Photolysis

Mechanistic studies of aromatic ketone-sensitized photoreduction of bis(acetylacetonato)copper(II)

1983 ◽  
Vol 61 (5) ◽  
pp. 801-808 ◽  
Author(s):  
Yuan L. Chow ◽  
Gonzalo E. Buono-Core ◽  
Bronislaw Marciniak ◽  
Carol Beddard
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Decay Rates ◽  
Polynuclear Aromatic Hydrocarbons ◽  
Aromatic Ketone ◽  
Quantum Yields ◽  
Triplet States ◽  
Quenching Rate ◽  
Triplet Energy

Bis(acetylacetonato)copper(II), Cu(acac)2, quenches triplet excited states of ketones and polynuclear aromatic hydrocarbons efficiently, but only aromatic ketones with high triplet energy successfully sensitize photoreduction of Cu(acac)2 in alcohols under nitrogen to give derivatives of aeetylacetonatocopper(I), Cu(acac). For the triplet state benzophenone-sensitized photoreduction of Cu(acac)2, the quantum yields of photoreduction (ΦC) and those of benzophenone disappearance (ΦB) were determined in methanol with various concentrations of Cu(acac)2. The values of the quenching rate constant, kq, determined from these two types of monitors on the basis of the proposed mechanism were in good agreement (6.89 ~ 7.35 × 109 M−1 s−1). This value was higher, by a factor of about two, than that obtained from the monitor of the benzophenone triplet decay rates generated by flash photolysis in the presence of Cu(acac)2. The quenching rate constants of various aromatic ketone and hydrocarbon triplet states by Cu(acac)2 were determined by flash photolysis to be in the order of the diffusion rate constant and the quantum yields of these photoreductions were found to be far from unity. Paramagnetic quenching, with contributions of electron exchange and charge transfer, was proposed as a possible quenching mechanism. For a series of aromatic ketone sensitizers with higher triplet energy, this mechanism was used to rationalize the observed high quenching rate constants in contrast to the low quantum yields of photoreduction.

THE OXIDATION OF NITRITE AND IODATE IONS BY HYPOCHLORITE IONS

1961 ◽  
Vol 39 (8) ◽  
pp. 1645-1651 ◽  
Author(s):  
M. W. Lister ◽  
P. Rosenblum
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Rate Constant ◽  
Hypochlorous Acid ◽  
Slow Stage ◽  
Iodate Ions

The oxidation of nitrite ions and of iodate ions by hypochlorite ions in aqueous solution has been examined. The oxidation of nitrite is really a reaction of hypochlorous acid, with the slow stage HOCl + NO2− + H2O → H3O+ + Cl− + NO3−. The rate constant is given by log k = 7.36−6450/RT (time in minutes, and the activation energy in calories). The oxidation of iodate is chiefly a reaction of hypochlorite ions, probably ClO− + IO3− → Cl− + IO4−, although the rate is somewhat increased by a higher concentration of hydroxide ions. The rate constant is given by log k = 16.15−26,100/RT. These results are compared with other oxidations by hypochlorite ions, to see if any general trends are apparent.

scholarly journals EFFECT OF DIATOMEAOUS EARTH TREATMENT USING HYDROGEN CHLORIDE AND SULFURIC ACID ON KINETICS OF CADMIUM(II) ADSORPTION

2010 ◽  
Vol 2 (2) ◽  
pp. 107-112
Author(s):  
Nuryono Nuryono ◽  
Narsito Narsito
Keyword(s):  
Aqueous Solution ◽  
Sulfuric Acid ◽  
Hydrogen Chloride ◽  
Rate Constant ◽  
Diatomaceous Earth ◽  
Adsorption Rate ◽  
Physical Interaction ◽  
First Order ◽  
Adsorption Rate Constant ◽  
Kinetics Of

In this research, treatment of diatomaceous earth, Sangiran, Central Java using hydrogen chloride (HCl) and sulfuric acid (H2SO4) on kinetics of Cd(II) adsorption in aqueous solution has been carried out. The work was conducted by mixing an amount of grounded diatomaceous earth (200 mesh in size) with HCl or H2SO4 solution in various concentrations for two hours at temperature range of 100 - 150oC. The mixture was then filtered and washed with water until the filtrate pH is approximately 7 and then the residue was dried for four hours at a temperature of 70oC. The product was used as an adsorbent to adsorb Cd(II) in aqueous solution with various concentrations. The Cd(II) adsorbed was determined by analyzing the rest of Cd(II) in the solution using atomic absorption spectrophotometry. The effect of treatment was evaluated from kinetic parameter of adsorption rate constant calculated based on the simple kinetic model. Results showed  that before equilibrium condition reached, adsorpstion of Cd(II) occurred through two steps, i.e. a step tends to follow a reaction of irreversible first order  (step I) followed by reaction of reversible first order (step II). Treatment with acids, either hydrogen chloride or sulfuric acid, decreased adsorption rate constant for the step I from 15.2/min to a range of 6.4 - 9.4/min.  However, increasing concentration of acid (in a range of concentration investigated) did not give significant and constant change of adsorption rate constant. For step II process,  adsorption involved physical interaction with the sufficient low adsorption energy (in a range of 311.3 - 1001 J/mol).     Keywords: adsorption, cdmium, diatomaceous earth, kinetics.

The Reaction of S(3P) Atoms with Molecular Oxygen

1971 ◽  
Vol 49 (10) ◽  
pp. 1659-1664 ◽  
Author(s):  
R. W. Fair ◽  
A. Van Roodselaar ◽  
O. P. Strausz
Keyword(s):  
Molecular Oxygen ◽  
Rate Constant ◽  
Ground State ◽  
Vacuum Ultraviolet ◽  
Flash Photolysis ◽  
Ultraviolet Region ◽  
Kinetic Spectroscopy ◽  
Vacuum Ultraviolet Region

The rate constant of the reaction of ground state S(3P) atoms with molecular oxygen, S(3P) + O2(X3Σg−) → SO(X3Σ−) + O(3P), has been determined as (1.7 ± 0.2) × 1012 cm3 mol−s− at 298 °K by means of kinetic spectroscopy in the vacuum ultraviolet region. The source of S(3P) atoms was the isothermal flash photolysis of COS in the presence of Ar or CO2.

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