Photochemische Primärreaktionen α‐verzweigter aliphatischer Ketone und Aldehyde in lösung

Blank, B.; Henne, Andreas; Fischer, Hanns

doi:10.1002/hlca.19740570348

Cited by 53 publications

(19 citation statements)

References 36 publications

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“…The proton CIDNP studies were performed at 100 MHz (Varian HA 100D) during continuous UV-irradiation (1000 W Xe/Hg lamp, filtered) and at 200 MHz (Bruker CXP 200) after laser pulse excitation (Lambda Physics EMG 100, XeCl) with arrangements described earlier [8,19]. Auxiliary experiments involved a Varian E-4 ESR spectrometer and a Perkin Elmer 204 fluorescence spectrometer.…”

Section: Methodsmentioning

confidence: 99%

Photoinduced electron transfer from naphthalenes to dicyanoethenes and subsequent radical ion processes studied by time resolved CIDNP

et al. 1993

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Abstract. Absolute net nuclear polarizations and their time and concentration dependences are reported for the products of laser pulse initiated electron transfer from naphthalene and naphthalene derivatives to 1,2-dicyanoethenes. They represent different prototype cases for radical ion pair formation and decay pathways and are used to test predictions from the highfield radical pair theory of CIDNP. By quantitative analyses reaction efficiencies, rate constants for degenerate electron exchange and nuclear relaxation times of the radical ions are obtained.

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Section: Methodsmentioning

confidence: 99%

Photoinduced electron transfer from naphthalenes to dicyanoethenes and subsequent radical ion processes studied by time resolved CIDNP

et al. 1993

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“…38,39 The subsequent radical reactions are where R ) (CH 3 ) 3 C and R′ ) CH 2 dC(CH 3 ) 2 for 2,2,4,4-tetramethylpentan-3-one, and R ) (CH 3 ) 2 COH and R′ ) CH 3 -COCH 3 or CH 2 dC(CH 3 )OH for 2,4-dihydroxy-2,4-dimethylpentan-3-one.…”

Section: Theorymentioning

confidence: 99%

Time-Resolved CIDNP Investigation of the Cross-Relaxation Mechanism of ¹H Nuclear Polarization

Batchelor

Fischer

1996

J. Phys. Chem.

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Time-resolved chemically induced dynamic nuclear polarization (CIDNP) studies are reported for radical reactions following laser pulse excitation of 2,2,4,4-tetramethylpentan-3-one and 2,4-dihydroxy-2,4-dimethylpentan-3-one in various solvents and of acetone in propan-2-ol-d 8 . The results show that crossrelaxation does not lead to polarization of the protons of 2-hydroxy-2-propyl and tert-butyl radicals at the 4.7 T field of the CIDNP experiment. Effects previously ascribed to cross-relaxation for the acetone/propan-2-ol system are due to side reactions and a fast solvent dependent nuclear relaxation. In radicals containing hydroxy groups, the CIDNP is strongly influenced by hydrogen bonding, which also affects their OH to CH disproportionation ratios. Auxiliary CIDEP experiments with 2,4-dihydroxy-2,4-dimethylpentan-3-one clearly indicate that the triplet mechanism polarization for this ketone is in absorption.

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“…[lo] [ll] [13] [14]. At low temperatures R1 can also be observed and a semidione type radical is found which arises by a photoreaction of the primary dione (7) with the solvent [lo] h v…”

Section: Solution Photochemistry Of Di-t-butylketone and Radical Reacmentioning

confidence: 99%

“…(14). 2k, is obtained at temperatures of fast decomposition by time resolved studies according to (15).…”

Section: Solution Photochemistry Of Di-t-butylketone and Radical Reacmentioning

confidence: 99%

Reaction Rates of t‐Butyl and Pivaloyl Radicals in Solution

Schuh

Hamilton

Paul

et al. 1974

Helvetica Chimica Acta

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Summary. The rate constants of the unimolecular decomposition of the pivaloyl radical (AD) and of the bimolecular self terminations of pivaloyl (k,) and t-butyl radicals (k,) in liquid mcthylcyclopentane arc determined by ESR.-spectroscopy :The viscosity dependence of K, is analysed with respect to diffusion control of tlie reaction.Comparison of k D values of different acyl radicals reveals a strong dependence of the activation energies on radical structure. . The studies were limited to small temperature ranges and few activation parameters were reported.In this paper, we extend our previous studies of photochemically produced radicals and their reaction rates [lo-121 to a determination of the absolute rate constants of self termination of the pivaloyl (R1= (CH,),CCO) and t-butyl (R2-(CH,),C.) radicals and of decomposition of pivaloyl (R1 --f R2 + CO) in a wide temperature range. The radicals are produced by photocleavage of di-t-butylketone in methylcyclopentane solutions. Steady state and time resolved ESR.-spectroscopy is applied.The particular chemical system was chosen for several reasons: Firstly, the radical reactions are rather simple and well known at room temperature [13] [14]. Secondly, the high quantum yield of cleavage leads to strong ESR.-signals of R1and R2 [lo] [ll]. Thirdly, though the self termination of t-butyl (R2) has been reported for several systems at or near room temperature 1-31 [5] 1-12] [15] the data show a considerable scatter and no activation parameters have been given. These would be highly instructive with respect to the possibIe diffusion control of this reaction in solution and for a comparison with tlie recent gas phase values [16]. Finally, the rate constant for decomposition of pivaloyl, a reaction reported for liquids [17], is of interest because a comparison with the known constants of other l)

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Photochemische Primärreaktionen α‐verzweigter aliphatischer Ketone und Aldehyde in lösung

Cited by 53 publications

References 36 publications

Photoinduced electron transfer from naphthalenes to dicyanoethenes and subsequent radical ion processes studied by time resolved CIDNP

Photoinduced electron transfer from naphthalenes to dicyanoethenes and subsequent radical ion processes studied by time resolved CIDNP

Time-Resolved CIDNP Investigation of the Cross-Relaxation Mechanism of ¹H Nuclear Polarization

Reaction Rates of t‐Butyl and Pivaloyl Radicals in Solution

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Photochemische Primärreaktionen α‐verzweigter aliphatischer Ketone und Aldehyde in lösung

Cited by 53 publications

References 36 publications

Photoinduced electron transfer from naphthalenes to dicyanoethenes and subsequent radical ion processes studied by time resolved CIDNP

Photoinduced electron transfer from naphthalenes to dicyanoethenes and subsequent radical ion processes studied by time resolved CIDNP

Time-Resolved CIDNP Investigation of the Cross-Relaxation Mechanism of 1H Nuclear Polarization

Reaction Rates of t‐Butyl and Pivaloyl Radicals in Solution

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Time-Resolved CIDNP Investigation of the Cross-Relaxation Mechanism of ¹H Nuclear Polarization