One-electron-transfer reactions of the couple sulfur dioxide/sulfur dioxide radical anion in aqueous solutions. Pulse radiolytic and cyclic voltammetric studies

1987 ◽  
Vol 91 (6) ◽  
pp. 1606-1611 ◽  
Author(s):  
P. Neta ◽  
Robert E. Huie ◽  
Anthony. Harriman
Keyword(s):  
Electron Transfer ◽  
Sulfur Dioxide ◽  
Aqueous Solutions ◽  
Radical Anion ◽  
Transfer Reactions ◽  
Cyclic Voltammetric ◽  
Electron Transfer Reactions ◽  
Voltammetric Studies ◽  
Cyclic Voltammetric Studies

Electron transfer reactions. Reaction of nitrones with potassium

1987 ◽  
Vol 65 (9) ◽  
pp. 2039-2049 ◽  
Author(s):  
Konda Ashok ◽  
Pallikkaparambil M. Scaria ◽  
Prashant V. Kamat ◽  
Manapurathu V. George
Keyword(s):  
Electron Transfer ◽  
Transfer Reactions ◽  
Radical Anions ◽  
Cyclic Voltammetric ◽  
Electron Transfer Reactions ◽  
Reduction Potentials ◽  
Dimeric Product ◽  
Voltammetric Studies ◽  
Electron Transfer Processes ◽  
Cyclic Voltammetric Studies

Treatment of nitrones (1a–d, 26a,b, 34, 49) with potassium in tetrahydrofuran (THF) gives rise to radical anion (2a–d, 27a,b, 35, 50) and dianion intermediates (3a–d, 28a,b, 36) through electron transfer reactions. These intermediates undergo further transformations to give a variety of products. Thus, the aldehydonitrones (1a–d) give the corresponding aldehydes (10a–c), carboxylic acids (25a–c), and azobenzenes (19a,d), whereas the ketonitrones (26a,b) give deoxygenation products (31a,b). The nitrone 34 gave a mixture of products consisting of benzoic acid (25a), dibenzyl (48), the dimeric product 38, and tetraphenylpyrazine (46), whereas 49 did not give any isolable product. Cyclic voltammetric studies have been employed to measure the reduction potentials for both one-electron and two-electron transfer processes, leading to the radical anions and dianions respectively. These intermediates have been characterized through their electronic spectra and they were quenched by oxygen. Pulse radiolysis of the nitrones 1a–d, 26a,b, 34, and 49 also gave the corresponding radical anions 2a–d, 27a,b, 35, and 50, characterized by their spectra.

Electron transfer reactions. Reaction of Δ2-oxazoline-5-ones and related substrates with potassium

1987 ◽  
Vol 65 (7) ◽  
pp. 1624-1630 ◽  
Author(s):  
Mohammed Muneer ◽  
Ravindra K. Tikare ◽  
Prashant V. Kamat ◽  
Manapurathu V. George
Keyword(s):  
Radical Anion ◽  
Transfer Reactions ◽  
Radical Anions ◽  
Cyclic Voltammetric ◽  
Subsequent Transformation ◽  
Reduction Potentials ◽  
Potassium Superoxide ◽  
Similar Product ◽  
Voltammetric Studies ◽  
Cyclic Voltammetric Studies

The reaction of several Δ2-oxazolin-5-ones (1a–c, 12) and bioxazolinones (17, 26) with potassium in THF has been investigated. Treatment of 1a with potassium in THF gave a mixture of dibenzamide (11a), N-benzoyl-C-phenylglycine (6a), and C-phenylglycine (10a). A higher yield of 11a was obtained, together with benzoic acid (9), when the reaction of 1a was carried out in THF saturated with oxygen. The reaction of 1b gave a mixture of β-phenylalanine (10b) and 9, whereas 1c gave a mixture of N-benzoyl-C,C-diphenylglycine (6c) and N-benzoyl-C,C-diphenylmethylamine (5c). Similarly, the reaction of 12 gave a mixture of α-benzamidocinnamic acid (15) and 9. The reaction of the bioxazolinone 17 with potassium gave a mixture of 11a, 6a, and 10a, along with an appreciable yield of 2,3,5,6-tetraphenylpyrazine (25), whereas 26 under analogous conditions gave a mixture of 15, 6b, and benzamide (29). Reasonable mechanisms, involving the initial formation of radical anion intermediates and their subsequent transformation to give the observed products, have been suggested. Potassium superoxide oxidation of some of these substrates gives similar product mixtures. Cyclic voltammetric studies have been carried out to measure the reduction potentials of 1a–c, 12, 17, and 26 in the generation of their radical anions. The radical anions of these substrates were also generated pulse radiolytically in methanol and their spectra showed absorption maxima in the region 295–350 nm.

Fast voltammetric studies of the kinetics and energetics of coupled electron-transfer reactions in proteins

2000 ◽  
Vol 116 ◽  
pp. 191-203 ◽  
Author(s):  
Fraser A. Armstrong ◽  
Raúl Camba ◽  
Hendrik A. Heering ◽  
Judy Hirst ◽  
Lars J. C. Jeuken ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Transfer Reactions ◽  
Electron Transfer Reactions ◽  
Voltammetric Studies

Effect of Pressure on Proton-Coupled Electron Transfer Reactions of Seven-Coordinate Iron Complexes in Aqueous Solutions

2005 ◽  
Vol 44 (21) ◽  
pp. 7624-7633 ◽  
Author(s):  
David Sarauli ◽  
Roland Meier ◽  
Gao-Feng Liu ◽  
Ivana Ivanović-Burmazović ◽  
Rudi van Eldik
Keyword(s):  
Electron Transfer ◽  
Aqueous Solutions ◽  
Iron Complexes ◽  
Transfer Reactions ◽  
Electron Transfer Reactions ◽  
Effect Of Pressure ◽  
Proton Coupled Electron Transfer

Electron transfer reactions. Reaction of nitrogen heterocycles with potassium

1990 ◽  
Vol 68 (6) ◽  
pp. 969-975 ◽  
Author(s):  
Mohammed Muneer ◽  
Prashant V. Kamat ◽  
Manapurathu V. George
Keyword(s):  
Benzoic Acid ◽  
Pulse Radiolysis ◽  
Nitrogen Heterocycles ◽  
Transfer Reactions ◽  
Radical Ions ◽  
Cyclic Voltammetric ◽  
Reduction Potentials ◽  
Potassium Superoxide ◽  
Voltammetric Studies ◽  
Cyclic Voltammetric Studies

The results of our studies on potassium-induced transformations of some selected nitrogen heterocycles are presented. The substrates under investigation include 2,3-diphenylindole (1a), 2,3-diphenyl-1-methylindole (1b), 1,2,3-triphenylindole (1c), 2,3,4,5-tetraphenylpyrrole (5a), 1,2,3,5-tetraphenylpyrrole (5b), 1-benzyl-2,3,5-triphenylpyrrole (5c), 2,4,5-triphenyloxazole (15a), 4,5-diphenyl-2-methyloxazole (15b), 2,4-diphenyl-5-methyloxazole (15c), and 2,4,5-triphenylimidazole (19). Treatment of 1a with potassium in THF gave 9H-dibenzo[a,c]carbazole (3a), whereas 1c gave a mixture of 9-phenyl-9H-dibenzo-[a,c]carbazole (3c) and 2,3-diphenylindole (1a). Under identical conditions, 1b gave only the cleavage product 1a. In contrast, when the reactions of 1a,c were carried out with potassium in THF saturated with oxygen, and with potassium superoxide in benzene containing 18-crown-6, a mixture of 2-benzamidobenzophenone (4a), the carbazoles 3a,c, and 1a was formed. Although no product was isolated on treatment of 5a with potassium in THF, the reaction of 5a with potassium in THF saturated with oxygen gave a mixture of tetraphenylpyrazine (7a), the benzoylaminostilbene 8a, the lactam 12a, benzamide (11a), and benzoic acid (14). Similar results were obtained in the reaction of 5a with potassium superoxide. The reaction of N-substituted pyrroles such as 5b,c with potassium gave the NH pyrrole 9b in each case, whereas the reaction of 5b,c with potassium in THF, saturated with oxygen, gave a mixture of 9b, the butanone 10b, the 1,4-dione 13b, the lactam 12b, the amides 11a–c, and benzoic acid (14). Attempted reactions of 5b,c with potassium superoxide did not give any isolable product; most of the starting material could be recovered unchanged in each case. A mixture of N-(1,2-diphenylethyl)benzamide (18a) and benzoic acid (14) was formed in the reaction of the oxazole 15a with potassium, whereas 15b,c, under analogous conditions, gave the N-vinylamides 17b,c and benzoic acid (14). In contrast, treatment of the imidazole 19 with potassium in THF did not give any product; however, when the reaction of 19 was carried out with potassium in THF saturated with oxygen, and with potassium superoxide, dibenzamide (21) was isolated, in each case.Radical ions have been invoked as intermediates in the transformation of the different substrates to the observed products. Cyclic voltammetric studies have been carried out to measure the reduction potentials of these radical anion intermediates. These radical anions have also been generated by pulse radiolysis in methanol, and their absorption spectra recorded. Keywords: nitrogen heterocycles, radical ions, potassium-induced transformations, pulse radiolysis, cyclic voltammetry.

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