Electron Transfer Reactions in Organic Chemistry. II. An Analysis of Alkyl Halide Reduction by Electron Transfer Reagents on the Basis of the Marcus Theory.

Eberson, Lennart; Karlsen, Jan; Mostad, Arvid; Samuelsson, Bertil; Enzell, Curt R.; Berg, Jan-Eric

doi:10.3891/acta.chem.scand.36b-0533

Cited by 100 publications

(57 citation statements)

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“…The mechanism of tryptophan fluorescence quenching by chloroform is unclear but may involve electron transfer (29,30) from the excited indole ring to the anesthetic. Whether the same mechanism is operative in the case of tryptophan residues located in different protein environments remains to be determined.…”

Section: Discussionmentioning

confidence: 99%

“…Because electron transfer (29,30) from the excited indole ring to chloroform might be responsible for the observed fluorescence quenching, which would involve free radical production, the reversibility of the protein-anesthetic interaction was examined. Samples of BSA with chloroform (35 mM) were examined fluorometrically and degassed with nitrogen for 45 min, at which time a second tryptophan emission spectrum was obtained.…”

Section: Methodsmentioning

confidence: 99%

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Binding of the Volatile Anesthetic Chloroform to Albumin Demonstrated Using Tryptophan Fluorescence Quenching

Johansson

1997

Journal of Biological Chemistry

143

115

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The site(s) of action of the volatile general anesthetics remain(s) controversial, but evidence in favor of specific protein targets is accumulating. The techniques to measure directly volatile anesthetic binding to proteins are still under development. Further experience with the intrinsic protein fluorescence quenching approach to monitor anesthetic-protein complexation is reported using chloroform. Chloroform quenches the steady-state tryptophan fluorescence of bovine serum albumin (BSA) in a concentration-dependent, saturable manner with a K d ‫؍‬ 2.7 ؎ 0.2 mM. Tryptophan fluorescence lifetime analysis reveals that the majority of the quenching is due to a static mechanism, indicative of anesthetic binding. The ability of chloroform to quench BSA tryptophan fluorescence was decreased markedly in the presence of 50% 2,2,2-trifluoroethanol, which causes loss of tertiary structural contacts in BSA, indicating that protein conformation is crucial for anesthetic binding. Circular dichroism spectroscopy revealed no measurable effect of chloroform on the secondary structure of BSA. The results suggest that chloroform binds to subdomains IB and IIA in BSA, each of which contains a single tryptophan. Earlier work has shown that these sites are also occupied by halothane. The present study therefore provides experimental support for the theory that structurally distinct general anesthetics may occupy the same domains on protein targets.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Binding of the Volatile Anesthetic Chloroform to Albumin Demonstrated Using Tryptophan Fluorescence Quenching

Johansson

1997

Journal of Biological Chemistry

143

115

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“…9 operates for 1d. Dissociative electron transfer has been discussed in terms of a modified Marcus-Hush model, 13,[14][15][16][17][18] and a quantitative agreement between experimental parameters and those calculated on this basis has been found both for electrochemical reduction and for homogeneous electron transfer from organic anions and from excited states. With a more effective acceptor such as 1c, quenching is more efficient (kq = 0.5kdiff) and, by analogy with the electrochemical reduction process, the photoinduced process is believed to occur mainly by path a.…”

mentioning

confidence: 94%

Photoinduced benzylation of 1,4-dimethoxynaphthalene by benzyl halides

Albini¹,

Siviero²,

Mella³

et al. 1995

J. Chem. Soc., Perkin Trans. 2

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Irradiation of 1,4-dimethoxynaphthalene (DMNH) in the presence of 4-substituted benzyl chlorides (X-C 6 H 4 CH 2 Cl, X = H, Cl, CN, or NO 2 ) in either acetonitrile or benzene solution results in benzylation of DMNH, predominantly at position 2 and to a lesser extent on the unsubstituted ring. Steady state and flash photolysis studies show that charge transfer between singlet excited DMNH and the chlorides is involved. The reaction occurs predominantly in-cage via concerted electron transfer and carbon-chlorine bond cleavage with X = H or Cl , while with X = NO 2 fragmentation of the benzyl chloride radical anion occurs out-of-cage, but the process in this case is much less efficient due to competing back electron transfer.--

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“…The classic work of Eberson shows that the l values for a wide variety of single electron transfer reagents in their reactions with a range of alkyl halides are in the 167-209 kJ mol À1 range. [31] Furthermore, earlier work of Moore suggests that the presence of large polarizable ligands on metals (such as I À ) results in lower l values for metal complexes. [32] Based on this analysis, a l value of approximately 167 kJ mol À1 best represents the system under study in this report.…”

mentioning

confidence: 99%

“…[29] The elegant work of Daasbjerg and co-workers provides a value~293 kJ mol À1 for self-exchange reorganization energy of Sm 3 + /Sm 2 + system in THF. [30] Since the self-reorganization energies of alkyl chlorides fall in the range of 234-377 kJ mol À1 [31] one would expect an average value for the total reorganization energy of the system to be closer to 293 kJ mol…”

mentioning

confidence: 99%

Photoinduced Electron Transfer Reactions by SmI₂ in THF: Luminescence Quenching Studies and Mechanistic Investigations

Prasad

Knettle

Flowers

2005

Chemistry A European J

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Photoluminescence quenching studies of SmI2 in dry THF were carried out in the presence of five different classes of compounds: ketone, alkyl chloride, nitrile, alkene and imine. The free energy change (DeltaG0) of the photoinduced electron transfer (PET) reactions was calculated from the redox potentials of the donor (SmI2) and acceptors. The bimolecular quenching constants (k(q)) derived from the Stern-Volmer experiments parallel the free energy changes of the PET processes. The observed quenching constants were compared with the theoretically derived electron transfer rate constants (k(et)) from Marcus theory and found to be in good agreement when a value of lambda = 167 kJ mol(-1) (40 kcal mol(-1)) was used for the reorganization energy of the system. A careful comparison of the excited state dynamics of SmII in the solid state to the results obtained in solution (THF) provides new insight in to the excited states of SmII in THF. The activation parameters determined for the PET reactions in SmI2/1-chlorobutane system are consistent with a less ordered transition state and high degree of bond reorganization in the activated complex compared to similar ground state reactions. Irradiation studies clearly show that SmI2 acts as a better reductant in the excited state and provides an alternative pathway for rate enhancement in known and novel functional group reductions.

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Electron Transfer Reactions in Organic Chemistry. II. An Analysis of Alkyl Halide Reduction by Electron Transfer Reagents on the Basis of the Marcus Theory.

Cited by 100 publications

References 0 publications

Binding of the Volatile Anesthetic Chloroform to Albumin Demonstrated Using Tryptophan Fluorescence Quenching

Binding of the Volatile Anesthetic Chloroform to Albumin Demonstrated Using Tryptophan Fluorescence Quenching

Photoinduced benzylation of 1,4-dimethoxynaphthalene by benzyl halides

Photoinduced Electron Transfer Reactions by SmI₂ in THF: Luminescence Quenching Studies and Mechanistic Investigations

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Electron Transfer Reactions in Organic Chemistry. II. An Analysis of Alkyl Halide Reduction by Electron Transfer Reagents on the Basis of the Marcus Theory.

Cited by 100 publications

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Binding of the Volatile Anesthetic Chloroform to Albumin Demonstrated Using Tryptophan Fluorescence Quenching

Binding of the Volatile Anesthetic Chloroform to Albumin Demonstrated Using Tryptophan Fluorescence Quenching

Photoinduced benzylation of 1,4-dimethoxynaphthalene by benzyl halides

Photoinduced Electron Transfer Reactions by SmI2 in THF: Luminescence Quenching Studies and Mechanistic Investigations

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Photoinduced Electron Transfer Reactions by SmI₂ in THF: Luminescence Quenching Studies and Mechanistic Investigations