Geminate ion recombination of electron and radical cation in non-polar liquid studied by laser-synchronized pico and subpicosecond pulse radiolysis

2003 ◽  
Author(s):  
Y. Yoshida ◽  
Y. Mizutani ◽  
T. Kozawa ◽  
M. Miki ◽  
S. Seki ◽  
...  
Keyword(s):  
Radical Cation ◽  
Pulse Radiolysis ◽  
Polar Liquid ◽  
Ion Recombination

Phenylalanine: Its ˙OH and SO4˙⁻-Induced Oxidation and Decarboxylation. A Pulse Radiolysis and Product Analysis Study

1993 ◽  
Vol 48 (6) ◽  
pp. 761-770 ◽  
Author(s):  
Degui Wang ◽  
Heinz-Peter Schuchmann ◽  
Clemens von Sonntag
Keyword(s):  
Radical Cation ◽  
Pulse Radiolysis ◽  
Side Reactions ◽  
Intramolecular Electron Transfer ◽  
Oh Radical ◽  
Product Analysis ◽  
Water Elimination ◽  
Deprotonation Reaction ◽  
Type Radical ◽  
Radical Yield

Phenylamine has been oxidized by radiolytically generated hydroxyl and sulfate radicals, the ensuing intermediates and their reactions have been studied by pulse radiolysis and product analysis in the absence and presence of oxidants such as Fe(CN)63- and O2. Upon OH radical attack, hydroxycyclohexadienyl-type radicals are mainly formed while Η-abstraction reactions can be neglected. In the presence of Fe(CN)63- these radicals are for the most part oxidized to the corresponding tyrosines (80%), except for the ipso-OH-adduct radicals (≈ 20%). It is concluded that ˙OH-addition is almost random, but with a slight avoidance of the metaposition relative to the ortho-, para- and ipso-positions. Oxygen adds reversibly to the OH-adduct radicals (kf = 1.8 × 108 dm3 mol-1 s-1, kr = 5.4 × 104 s-1). In this case, tyrosine formation occurs by HO2˙-elimination. However, due to side reactions, tyrosine formation only reaches 52% of the OH radical yield. The tyrosine yield drops to 10% in the absence of an oxidant.Upon SO4˙⁻-attack, decarboxylation becomes a major process (33% of SO4˙⁻) alongside the production of tyrosines (43%). Here, with Fe(CN)63- as the oxidant the formation of p-Tyr (18.5%) and m-Tyr (16.5%) is preferred over o-Tyr formation (8.5%). It is believed that in analogy to other systems a radical cation is formed immediately upon SO4˙⁻-attack which either reacts with water under the formation of hydroxycyclohexadienyl-type (“OH-adduct”) radicals, or decarboxylates after intramolecular electron transfer. The radical cation can also arise indirectly through H+-catalysed water elimination from the ˙OH-adduct radicals. At pH 2 and a dose rate of 0.0046 Gy s-1 CO2 formation matches the OH radical yield when ˙OH is the attacking radical. Below pH 2, G(CO2) decreases with falling pH. This indicates the occurrence of another, unimolecular, pathway under these conditions competing effectively with decarboxylation. This appears to be a relatively slow deprotonation reaction of the carboxylprotonated phenylalanine radical cation which gives rise to the benzyl-type radical.

Picosecond pulse radiolysis studies on geminate ion recombination in saturated hydrocarbon

1983 ◽  
Vol 21 (1-2) ◽  
pp. 45-52 ◽  
Author(s):  
S. Tagawa ◽  
M. Washio ◽  
H. Kobayashi ◽  
Y. Katsumura ◽  
Y. Tabata
Keyword(s):  
Pulse Radiolysis ◽  
Saturated Hydrocarbon ◽  
Picosecond Pulse ◽  
Ion Recombination

Subpicosecond Pulse Radiolysis Study on Geminate Ion Recombination Process in n-Dodecane

2005 ◽  
pp. 479-481
Author(s):  
Yoichi Yoshida ◽  
Akinori Saeki ◽  
Takahiro Kozawa ◽  
Jinfeng Yang ◽  
Seiichi Tagawa
Keyword(s):  
Pulse Radiolysis ◽  
Recombination Process ◽  
Ion Recombination

Geminate-ion kinetics with competing ion fragmentation in nonpolar liquids with halocarbons

1990 ◽  
Vol 68 (9) ◽  
pp. 918-924 ◽  
Author(s):  
Rolf E. Bühler
Keyword(s):  
Low Temperatures ◽  
Pulse Radiolysis ◽  
Room Temperature ◽  
Ion Concentration ◽  
Geminate Recombination ◽  
Rate Law ◽  
Ion Fragmentation ◽  
Nonpolar Liquids ◽  
Ion Recombination ◽  
Semi Empirical

The semi-empirical rate law for geminate-ion recombination by van den Ende, Warman, and Hummel, which predicts a linear dependence of the ion concentration with t−0.6, is modified to include simultaneous ion fragmentation. The theory is applied to the kinetics, as observed by pulse radiolysis of liquid methylcyclohexane (MCH) solutions of N2O, CHCl3, or tert-butylchloride (t-BuCl) at low temperatures. In MCH saturated with N2O (−130 °C), the solvent cation (MCH+, λmax = 550 nm) moves about 400 times faster than prediced by diffusion. With the known conductivity data at room temperature, an activation energy of about 2.7 kJ/mol can be derived. The solvent cation MCH+ does not appear to fragment. With t-BuCl added to MCH (−134 °C), MCH+ (λmax = 550 nm) and t-BuCl− (λmax = 450 nm) are observed simultaneously. The initial kinetics corresponds to the parent ion (MCH+) recombination with t-BuCl−. Then the MCH+ fragmentation with k1(−134 °C) = 3 × 105 s−1 is observed, followed by the geminate recombination of some fragment cation with t-BuCl−. The fragment cation recombines 300 times slower than the parent cation. With CHCl3 added to MCH (−130 °C), the MCH+ absorption is hidden within the [Formula: see text] band (λmax = 470 nm); however, the fragmentation is detected from kinetic analysis to occur in about 2 × 106 s−1. The modified t−0.6 rate law appears to be a very useful tool to study simultaneous ion recombination and ion fragmentation.

Subpicosecond Pulse Radiolysis Study of Geminate Ion Recombination in Liquid Benzene

2003 ◽  
Vol 32 (9) ◽  
pp. 834-835 ◽  
Author(s):  
Kazumasa Okamoto ◽  
Akinori Saeki ◽  
Takahiro Kozawa ◽  
Yoichi Yoshida ◽  
Seiichi Tagawa
Keyword(s):  
Pulse Radiolysis ◽  
Liquid Benzene ◽  
Ion Recombination

Photochemical Nitration by Tetranitromethane. XVII. The Regiochemistry of Adduct Formation in the Photochemical Reaction of 1-Methylnaphthalene and Tetranitromethane

1994 ◽  
Vol 47 (8) ◽  
pp. 1591 ◽  
Author(s):  
JL Calvert ◽  
L Eberson ◽  
MP Hartshorn ◽  
n Maclaga ◽  
WT Robinson
Keyword(s):  
Crystal Structure ◽  
Charge Transfer ◽  
Radical Cation ◽  
Photochemical Reaction ◽  
Charge Transfer Complex ◽  
Adduct Formation ◽  
X Ray ◽  
Analogous Manner ◽  
Structure Determinations ◽  
Ion Recombination

Photolysis of the 1-methylnaphthalene/tetranitromethane charge-transfer complex yields the triad of 1-methylnaphthalene radical cation, nitrogen dioxide and trinitromethanide ion. Recombination of this triad gives predominantly 4-methyl-t-2-nitro-r-1-trinitromethyl-1,2- dihydronaphthalene (1), the epimeric 1-methyl-1-nitro-4-trinitromethyl-1,4-dihydronaphtha-lenes (2) and (3), 8-methyl-c-4-trinitromethyl-1,4-dihydronaphthalen-r-l-ol (4), nitro cyclo -adduct (5), 8-methyl-c-4-trinitromethyl-1,4-dihydronaphthalen-r-l-ol (6), hydroxy cyclo-adduct (7) and 4-methyl-t-1-trinitromethyl-1,2-dihydronaphthalen-r-2-ol (8). Adducts (1)- (3), (5), (7) and (8) are formed by attack of the trinitromethanide ion at C4 of the 1-methylnaphthalene radical cation, while adducts (4) and (6) are formed by corresponding attack at C5. Adduct (1) undergoes thermal cycloaddition to give the nitro cycloadduct (5) and it is assumed that the hydroxy cycloadduct (7) is formed in analogous manner from 4-methyl-t-1-trinitromethyl-1,2-dihydronaphthalen-r-2-ol (8). X-Ray crystal structure determinations are reported for adducts (1), (3)-(5) and (7).

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