Polar substituent and solvent effects on the kinetics of radical reactions with thiols

Tronche, Christopher; Martinez, Felix N.; Horner, John H.; Newcomb, Martin; Senn, Martin; Giese, Bernd

doi:10.1016/0040-4039(96)01241-5

Cited by 65 publications

(88 citation statements)

References 13 publications

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“…The rates of H-transfer from alkanethiols to alkyl radicals depend strongly upon the radical substituents. [21,22] For example, the a,b-dialkoxyalkyl radical reacts about 10 times slower than the analogous unsubstituted alkyl radical. A reasonable assumption for the reaction of C2' radical 11 with GSH is a rate constant of about 10 6 m À1 s…”

Section: Independent Generation Of the 2'-adenosinyl Radical (11)mentioning

confidence: 99%

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Selective Generation and Reactivity of 5′‐Adenosinyl and 2′‐Adenosinyl Radicals

Chatgilialoglu

Duca

Ferreri

et al. 2004

Chemistry A European J

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The reaction of hydrated electrons (e(-)(aq) with 8-bromoadenosine 7 has been investigated by radiolytic methods coupled with product studies. Pulse radiolysis revealed that one-electron reductive cleavage of the C-Br bond gives the C8 radical 8 followed by a fast radical translocation to the sugar moiety. The reaction is partitioned between C5' and C2' positions in a 60:40 ratio leading to 5'-adenosinyl radical 9 and 2'-adenosinyl radical 11. This radical translocation from C8 to different sites of the sugar moiety has also been addressed computationally by means of DFT B3LYP calculations. In addition, ketone 21 was prepared and photolyzed providing an independent generation of C2' radical 11. Both C5' and C2' radicals undergo unimolecular reactions. Radical 9 attacks adenine with a rate constant of 1.0 x 10(4) s(-1) and gives the aromatic aminyl radical 10, whereas C2' radical 11 liberates adenine with a rate constant of 1.1 x 10(5) s(-1).

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Section: Independent Generation Of the 2'-adenosinyl Radical (11)mentioning

confidence: 99%

“…, [21] which suggests a rate constant k f of about 2 î 10 5 s À1 for the b-elimination. This is in good agreement with the rate observed in the radiolysis studies.…”

mentioning

confidence: 99%

Selective Generation and Reactivity of 5′‐Adenosinyl and 2′‐Adenosinyl Radicals

Chatgilialoglu

Duca

Ferreri

et al. 2004

Chemistry A European J

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“…Hydrogen atoms add very fast to 1,2-dialkyl substituted olefins [Equation (4) ] [7] to give the hydrogenated olefin. Therefore, in the presence of unsaturated fatty acid derivatives, the direct photolysis of alkanethiols in solution will afford large amounts of hydrogenated products.…”

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confidence: 99%

The Kinetics of Z/E Isomerization of Methyl Oleate Catalyzed by Photogenerated Thiyl Radicals

et al. 2005

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The reaction of beta-mercaptoethanol with methyl oleate in tertbutyl alcohol was investigated under photochemical conditions. The time-dependent Z/E isomerization of the unsaturated moiety as well as the thiol-adduct formation were analyzed on the basis of radical generation rates and established rate constants. This provides precise room-temperature rate constants for the reversible thiyl radical addition to both Z and E isomers. The rate constants for HOCH2CH2S* addition to the Z and E forms were found to be 1.6 x 10(5) and 2.9 x 10(5) M(-1) S(-1), respectively. For the beta-elimination of the thiyl radical from the alkyl radical adduct, the rate constants were 1.7 x 10(7) and 1.6 x 10(8) S(-1), the faster associated with the formation of the E isomer. DFT-BB1K calculations on 2-butene assign this large preference of fragmentation for the E isomer to a lower activation barrier for the formation of the E transition state from the equilibrium radical adduct structure.

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“…1 H NMR (CDCl 3 with CD 3 OD): d 7.17 (d, J 1.2 Hz, 1 H, H-6), 6.70 (dd, J 4.1, 9.7 Hz, 1 H, H-1'), 5.04 ± 5.07 (m, 1 H, H-3'), 4.18 ± 4.21 (m, 2 H, H-5'), 3.24 (ddq, J 9.7, 17.3, 2.0 Hz, 1 H, H-2'), 2.86 (br s, 1 H, OH), 2.52 (ddq, J 4.1, 17.3, 1.5 Hz, 1 H, H-2'), 1.91 (d, J 1.2 Hz, 3 H, Me-5); 13 C NMR (CDCl 3 with CD 3 OD): d 164.3 (C q , C-4), 156.7 (C q , C-4'), 150.3 (C q , C-2), 135.1 (C t , C-6), 111.6 (C q , C-5), 95.5 (C t , C-3'), 84.7 (C t , C-1'), 56.4 (C s , C-5'), 36.1 (C s , C-2'), 11.9 (C p , Me-5); FAB-MS (NBA KCl): m/z 263 [MK] , 225 [M1] . Because of the lability of the substance a correct elemental analysis could not be achieved.…”

Section: Identification Of Ketoaldehyde 16mentioning

confidence: 99%

“…for GSH, [13] a cleavage rate coefficient of k cleav 70 s À1 was Figure 1. Ratio of the elimination product 6 to the H-abstraction products 14 a 14 b of radical 12 as a function of the glutathione diester (GSH) concentration in buffered water solution (pH 7.0) at 20 8C.…”

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confidence: 99%

Electron Transfer in DNA from Guanine and 8-Oxoguanine to a Radical Cation of the Carbohydrate Backbone

et al. 2000

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Photolysis of a 4'-pivaloyl-substituted nucleotide in single- and double-stranded DNA (1) generated an enol ether radical cation 4 that was reduced to enol ether 17 by electron transfer from the nearest guanoside (G). Variation of the nucleotide sequence demonstrated a strong distance dependence of this electron-transfer rate with beta = 1.0 +/- 0.1 A(-1). When 8-oxoguanosine (G(oxo)) was used as the electron donor, the rate of the electron transfer increased by a factor of 4 but the distance dependence of the transfer remained unchanged within experimental error. In single strands, the number of intervening A, T, and C nucleotides had a much smaller effect; the rate remained nearly constant for two, three, or four intervening nucleotides. This is explained by the flexibility of the single-stranded oligonucleotides.

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Polar substituent and solvent effects on the kinetics of radical reactions with thiols

Cited by 65 publications

References 13 publications

Selective Generation and Reactivity of 5′‐Adenosinyl and 2′‐Adenosinyl Radicals

Selective Generation and Reactivity of 5′‐Adenosinyl and 2′‐Adenosinyl Radicals

The Kinetics of Z/E Isomerization of Methyl Oleate Catalyzed by Photogenerated Thiyl Radicals

Electron Transfer in DNA from Guanine and 8-Oxoguanine to a Radical Cation of the Carbohydrate Backbone

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