Disproportionation of Cr V generated by the radiation-induced reduction of Cr VI in aqueous solution containing formate: a pulse radiolysis study

1996 ◽  
Vol 92 (21) ◽  
pp. 4173 ◽  
Author(s):  
George V. Buxton ◽  
Fathi Djouider
Keyword(s):  
Aqueous Solution ◽  
Pulse Radiolysis ◽  
Radiation Induced

Studies of radiation-induced reactions of ethylene in aqueous solution II. Reactions in the presence of oxygen as studied by pulse radiolysis and γ -irradiation techniques

1967 ◽  
Vol 300 (1463) ◽  
pp. 443-454 ◽  
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Peroxide ◽  
Rate Constants ◽  
Pulse Radiolysis ◽  
Major Product ◽  
Peroxy Radicals ◽  
Ferrous Ions ◽  
Constant Composition ◽  
Γ Irradiation ◽  
Radiation Induced

The radiolysis of dilute aqueous solutions containing ethylene and oxygen has been investigated. Pulse radiolysis was used to measure the rate constants for the addition of hydroxyl radicals to ethylene, the binary decomposition of the resulting hydroxyethyl radicals and their addition to ethylene and reaction with oxygen to yield peroxy radicals. The rate constants have also been determined for the mutual interaction of the peroxy radicals and their reaction with ferrous ions. The principal products of γ -irradiation were aldehydes and organic hydroperoxides. Hydrogen peroxide was found in yields close to the molecular yield from water. The polymer produced in the absence of oxygen was not formed, and glycollaldehyde, reported as a major product by previous workers, could not be detected. At constant composition of the gas mixtures, product yields were unaffected by total pressure in the range up to 40 atm, but were strongly dependent on the proportion of oxygen. Aldehyde yields were markedly greater at pH 1.2 than in neutral solution. The influence of ferrous ions an d of added hydrogen peroxide has been determined. The pulse radiolysis and γ -irradiation experiments complement one another and show that the radiation-induced oxidation of ethylene in aqueous solution involves the same primary reactions as occur in the absence of oxygen, followed by the formation and further reactions of peroxy radicals.

Nanosecond pulse radiolysis of methanolic and aqueous solutions of readily oxidizable solutes

1972 ◽  
Vol 328 (1572) ◽  
pp. 23-36 ◽  
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Pulse Radiolysis ◽  
Nanosecond Pulse ◽  
Forward Rate ◽  
Mechanism Of Formation ◽  
Methoxy Radicals ◽  
Nanosecond Pulses ◽  
Radiation Induced ◽  
Pure Methanol

The formation of I ̅ 2 and (CNS) ̅ 2 has been observed in aqueous solution of KI and KCNS respectively following irradiation with nanosecond pulses of 3 MeV electrons. In both cases it is necessary to invoke the intermediate and consecutive formation of two species which do not absorb light at the monitoring wavelength. The following mechanism is invoked for the formation of X ̅ 2 (where X ̅ = I ̅ or CNS ̅ ): OH + X ̅ → HOX ̅ , (5 a ) HOX ̅ → OH ̅ + X , (5 b ) X ̅ + X ̅ ⇌ X ̅ 2 (6) For the iodide solutions the rate constants were evaluated as k 5 a = k 6 = (1.21 + 0.08) x 10 10 1 mol -1 s -1 and k 5 b = (1.2 ± 1.0) x 10 8 s -1 . In the case of the thiocyanate solutions k 5 a = k 6 = (1.08 ± 0.10) x 10 10 1 mol -1 s -1 and HOCNS ̅ is estimated to have a lifetime of about 5 ns. The radiation induced oxidation of N, N , N', N' -tetramethyl- p -phenylenediamine (TMPD) to Wurster’s Blue cation (TMPD + ) has been observed by nanosecond pulse radiolysis of solutions of TMPD in methanol. It is concluded that the oxidation of TMPD is by methoxy radicals and the rate constants k CH 2 O. +TMPD and k CH 2 O.+CH 3 OH are evaluated to be (6·10 ± 0·05) x 10 9 1 mol -1 s -1 and 2·63 + 0·10 x 10 5 1 mol -1 s -1 respectively. Thus the half-life of methoxy radicals in pure methanol is 106 ns. The formation of I ̅ 2 was observed in methanolic solutions of KI. The oxidizing species is thought to be the m ethoxy radical and the mechanism of formation of I ̅ 2 is by the reactions CH 3 O + I ̅ → CH 3 O ̅ + I ̅ , I + I ̅ ⇌ I ̅ 2 . The rate constant of reaction (1) and the forward rate of the equilibrium (2) are estimated to be (3·7 ± 0.3) x 10 9 1 mol -1 s -1 an d (2·6 ± 0·4) x 10 10 1 mol -1 s -1 respectively. Observations on the transient u.v. absorption band of pulse irradiated methanol suggest that the spectra of CH 3 O and CH 2 OH are very similar for λ = 250 to 320 nm.

Pulse radiolysis: evidence for the reaction of HO2 with NO2 in aqueous solution

1978 ◽  
Vol 56 (14) ◽  
pp. 1961-1964 ◽  
Author(s):  
Harry Callender Sutton ◽  
William Arthur Seddon ◽  
Fred Charles Sopchyshyn
Keyword(s):  
Aqueous Solution ◽  
Formic Acid ◽  
Rate Constant ◽  
Pulse Radiolysis ◽  
First Order ◽  
Data Support ◽  
Radiation Induced ◽  
Three Stages ◽  
Ph Range ◽  
Saturated Solutions

Nitroform is the major radiation induced species observed after the pulse radiolysis of acidic oxygen saturated solutions of tetranitromethane (TNM) and formic acid. It is formed in three stages, of which a major component at pH < 3 is first order with t1/2 = 49 s, independent of [TNM] and pH. Evidence is provided for the reactions[Formula: see text]in which k14 = 0.014 ± 0.002 s−1. The data support similar conclusions reached previously in rapid mixingexperiments (1) from which it was concluded that k3 = 4 × 109 dm3 mol−1 s−1.Analysis of the fastest component of nitroform production over the pH range 1–4 shows that the COOH radical reduces TNM to nitroform with a rate constant about four times greater than that for its reaction with oxygen to produce HO2.

Pulse radiolysis of polymers in aqueous solution. Kinetics study

1997 ◽  
Vol 94 ◽  
pp. 244-250 ◽  
Author(s):  
I Janik ◽  
P Kujawa ◽  
P Ulanski ◽  
JM Rosiak
Keyword(s):  
Aqueous Solution ◽  
Pulse Radiolysis ◽  
Kinetics Study ◽  
Solution Kinetics

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
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