Enol intermediates in photoreduction and type I cleavage reactions of aliphatic aldehydes and ketones

Blank, B.; Henne, Andreas; Laroff, Gary P.; Fischer, Hanns

doi:10.1351/pac197541040475

Cited by 55 publications

(20 citation statements)

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“…Alpha cleavage at these wavelengths does not occur [Yang, 1967;Henne and Fischer, 1975], but the species does undergo H abstraction. The same is true of propanal [Blank et al, 1975], although in this case some alpha cleavage may occur in the 290 nm _< X _< 310 nm region [Chen et al, 1973]. Acetone in aqueous solution also undergoes H atom abstraction following irradiation at 300 nm _< X To summarize, the case for carbonyl photochemistry in attoospheric aerosols is tenuous.…”

Section: But May Results As Well From Reactions In the Gas Phase And Imentioning

confidence: 93%

Chemistry within aqueous atmospheric aerosols and raindrops

Graedel¹,

Weschler²

1981

Reviews of Geophysics

392

154

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1] Chemical and physical Earth models agree little as to the radioactive power of the planet. Each predicts a range of radioactive powers, overlapping slightly with the other at about 24 TW, and together spanning 14-46 TW. Approximately 20% of this radioactive power (3-8 TW) escapes to space in the form of geoneutrinos. The remaining 11-38 TW heats the planet with significant geodynamical consequences, appearing as the radiogenic component of the 43-49 TW surface heat flow. The nonradiogenic component of the surface heat flow (5-38 TW) is presumably primordial, a legacy of the formation and early evolution of the planet. A constraining measurement of radiogenic heating provides insights to the thermal history of the Earth and potentially discriminates chemical and physical Earth models. Radiogenic heating in the planet primarily springs from unstable nuclides of uranium, thorium, and potassium. The paths to their stable daughter nuclides include nuclear beta decays, producing geoneutrinos. Large subsurface detectors efficiently record the energy but not the direction of the infrequent interactions of the highest-energy geoneutrinos, originating only from uranium and thorium. The measured energy spectrum of the interactions estimates the relative amounts of these heatproducing elements, while the intensity estimates planetary radiogenic power. Recent geoneutrino observations in Japan and Italy find consistent values of radiogenic heating. The combined result mildly excludes the lowest model values of radiogenic heating and, assuming whole mantle convection, identifies primordial heat loss. Future observations have the potential to measure radiogenic heating with better precision, further constraining geological models and the thermal evolution of the Earth. This review presents the science and status of geoneutrino observations and the prospects for measuring the radioactive power of the planet.

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Section: But May Results As Well From Reactions In the Gas Phase And Imentioning

confidence: 93%

Chemistry within aqueous atmospheric aerosols and raindrops

Graedel¹,

Weschler²

1981

Reviews of Geophysics

392

154

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“…The factor of 0.1 represents the detection limit of the HPLC reacted by combination (23). Thus, it is difficult to predict a priori the fraction of combination.…”

Section: Aah0xch3c(h)=ch2+ch3c(oh)=ch) =mentioning

confidence: 99%

Radical-induced degradation of a lignin model compound. Decomposition of 1-phenyl-2-phenoxyethanol

Huang¹,

Pagé²,

Wayner³

1995

Can. J. Chem.

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Reaction of 1-phenyl-2-phenoxyethanol(1) with thermally or photochemically generated tertbutoxyl radicals leads, via the intermediate ketyl radical, to the formation of the corresponding ketone, aphenoxyacetophenone (4), as the only product at low conversion under an inert atmosphere. An approximately twofold increase in the product yield is observed when the reactions are carried out under oxygen. Under the photochemical conditions it is shown that 4 is the primary product and that acetophenone and phenol are formed as a result of secondary photolysis of 4. These data suggest that the rate constant for fragmentation of the ketyl radical derived from 1 is on the order of 10 s-I at 298 K and contradict a report in the literature that suggests a rate constant of >lo6 sf'. The relevance of this study to the photodegradation of lignin and consequent photoyellowing is discussed and a revised mechanism for the photoyellowing of pulp is proposed.Key words: ketyl radical, photochemical degradation, thermal degradation, lignin.ResumC : Lorsqu'on effectue la reaction du 1-phCnyl-2-phCnoxyCthanol (1) avec des radicaus tert-butoxyles gCnCrCs thermiquement ou photochimiquement B de faibles taux de conversion, sous une atmosphere inerte, le seul produit 2. se former, par le biais du radical cCtyle intermediaire, est la cCtone correspondante, a-phCnoxyacCtophtnone (4). Lorsqu'on effectue la rCaction sous une atmosphere d'oxygbne, le rendement en produit est approximativement double. Dans des conditions photochimiques, il a Ct C dCmontrC que 4 est le produit primaire et que de llacCtophtnone et du phCnol se forment par le biais d'une photolyse secondaire de 4. Ces donnCes suggbrent que la constante de vitesse de fragmentation du radical cCtyle dCrivC de 1 est de l'ordre de 10 s-', B 298 K, et elles sont en contradiction avec des donnCes de la 1ittCrature qui suggbrent que la constante de vitesse est >lo6 S-I. On discute de IYintCr&t de cette Ctude pour la photodCgradation de la lignine et jaunissement photochimique qui en dCcoule et on propose un mCcanisme rCvisC pour jaunissement de la pulpe.

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“…A free radical mechanism which involves decarbonylation and radical recombination was suggested on the basis of the analyses of the chemical products (7)(8)(9) and CIDNAP studies (11). The question of whether the mechanism is concerted, or stepwise, involving the formation of phenylacetyl radical and benzyl radical, has been decided in favor of the latter (10) by experiments of radical recombination of these two radicals with the nitroxide 2,2,6,6-tetramethylpiperidine-1-oxyl.…”

Section: P I C~h~c H Z C C H Z C~h~mentioning

confidence: 99%

Spin-trapping with 2-methyl-2-nitrosopropane: photochemistry of carbonyl-containing compounds. Methyl radical formation from dimethyl sulfoxide

Rosenthal¹,

Mossoba²,

Riesz³

1982

Can. J. Chem.

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The photochemical reactions of several carbonyl-containing compounds investigated by spin-trapping with 2-methyl-2-nitrosopropane revealed different modes of scission depending on the structure of the initial compound. Thus, in photo-Fries rearrangements, the acyl radical was detected. 1,3-Diphenyl-2-propanone decarbonylated to yield the benzyl radical. Finally, valerophenone yielded the radicals expected by γ-hydrogen abstraction. In a dark reaction, dimethyl sulfoxide reacts with NaOH to generate methyl radicals. The latter result suggests the need for caution in the use of dimethyl sulfoxide with 2-methyl-2-nitrosopropane for the detection of hydroxyl radicals.

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Enol intermediates in photoreduction and type I cleavage reactions of aliphatic aldehydes and ketones

Abstract: Abstract

Cited by 55 publications

References 0 publications

Chemistry within aqueous atmospheric aerosols and raindrops

Chemistry within aqueous atmospheric aerosols and raindrops

Radical-induced degradation of a lignin model compound. Decomposition of 1-phenyl-2-phenoxyethanol

Spin-trapping with 2-methyl-2-nitrosopropane: photochemistry of carbonyl-containing compounds. Methyl radical formation from dimethyl sulfoxide

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