Molecular photochemistry. L. Molecular photochemistry of alkanones in solution. .alpha.-Cleavage, hydrogen abstraction, cycloaddition, and sensitization reactions

Turro, Nicholas J.; Dalton, J. C.; Dawes, K.; Farrington, G K; Hautala, Richard R.; Morton, Douglas R.; Niemczyk, Mark P.; Schore, Neil E.

doi:10.1021/ar50051a002

Cited by 192 publications

(80 citation statements)

References 19 publications

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“…However, for the intermediate diradical which would result from fission remote from the four-membered ring, H I is geometrically inaccessible such that ring closure should compete efficiently and 20 is thus the aldehyde expected. For carvonecamphor (21), the ester arises from a tert-cyclobutyl radical in preference to a primary alkyl radical in accord with expectations. Similarly the spiro ketone 23 gives the anticipated product arising from a tert-cyclobutyl radical intermediate.…”

Section: Ch3 Ch3supporting

confidence: 79%

Photoisomerization of Bicyclo[3.1.1]heptan-2-ones in Methanol: Chemical Transformations of 'Verbanones'

Fallis¹

1975

Can. J. Chem.

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ALEX G. FALLIS. Can. J. Chern. 53, 1657 (1975. The products (predominantly unsaturated aldehydes) from photolysis in methanol of a series of 6,6-dirnethylbicyclo[3.1 .l]heptan-2-ones are reported. These results are rationalized on the basis of stereochernical interactions and the apparent preference for cleavage to occur adjacent to the less highly substituted a-carbon but more stable alkyl radical. It is concluded that the photochemical behavior of a-cyclobutyl ketones displays a closer parallel to the a-cyclopropyl ketones than previously recognized and that cleavage will occur preferentially on the side of the carbonyl group remote from the four-membered ring whenever possible. The synthetic steps involved in the preparation of the ketones from 'pinene' precursors are described.ALEX G. FALLIS. Can. J. Chem. 53, 1657Chem. 53, (1975. On rapporte les produits (principalement des aldkhydes non-saturks) formis lors de la photolyse dans le methanol d'une sQie de dimkthyl-6,6 bicyclo[3.1.1]heptanones-2. On rationalise les resultats en se basant sur les interactions sterkochimiques et la prkfkrence apparente pour que la coupure se produise dans la position adjacente a celle du carbone a moins substitue rnais posskdant le radical alkyle le plus stable. On en conclut que le comportement photochimique des a-cyclobutyl dtones montre un parallklisrne plus pres de celui des a-cyclopropyl cetones qu'il n'avait kte reconnu auparavant; de plus, chaque fois que cette coupure sera possible, la coupure se produira prkferentiellement sur le c6tk du groupement carbonyle Cloignk du cycle a quatre rnernbres. On dkrit les ktapes synthktiques irnpliqukes dans la prkparation des cktones a partir de prkurseur du type 'pinhe'.[Traduit par le journal]

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Section: Ch3 Ch3supporting

confidence: 79%

Photoisomerization of Bicyclo[3.1.1]heptan-2-ones in Methanol: Chemical Transformations of 'Verbanones'

Fallis¹

1975

Can. J. Chem.

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“…Since the term K1(1 + K&l < 1, we can estimate k,, and k&'2 by eqs 14 and 13, respectively, (4 In our previous report on inter-HT, we obtained k,, = 9.1 X lo6 s-1 and k&$ = 1.2 X lo7 M-1 ~-1 . l~ Considering these values with eqs a and b, we estimate k,, lo7 s-l and k&' 2 N lo7 M-l s-1 for intra-HT.…”

Section: (14)mentioning

confidence: 86%

Laser flash photolysis studies on intramolecular hydrogen atom transfer of [(hydroxynaphthyl)propyl]benzophenone and intramolecular proton-induced electron transfer of [(methoxynaphthyl)propyl]benzophenone via triplet exciplexes

Sekiguchi¹,

Yamaji²,

Tatemitsu³

et al. 1993

J. Phys. Chem.

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Laser photolysis studies at 355 nm have been carried out on the intramolecular hydrogen atom transfer (intra-HT) reaction of [(hydroxynaphthyl)propyl] benzophenone, BP-(CH&-ROH, and the proton-induced intramolecular ionization (intra-pion) reaction of [ (methoxynaphth yl)propyl]benzophenone, BP-(CH2)3-ROMe, in acetonitrilewater (4:l v/v) at 295 K. After 355-nm laser pulsing to BP-(CH&-ROH and BP-(CH2)3-ROMe, the intramolecular triplet energy transfer (intra-ET) reactions from the triplet moiety (3BP*) to the naphthol (ROH) and methoxynaphthalene (ROMe) moieties occur to yield BP-(CH2)3-3ROH* and BP-( C H Z )~-~R O M~* on a nanosecond time scale. The former triplet molecule (BP-(CH2)3-3ROH*) undergoes intramolecular hydrogen atom transfer (intra-HT) with an efficiency (&T) of unity to yield a biradical molecule with benzophenone ketyl radical (>COH-) and naphthoxy radical (ROO) moieties (>C0H-(CH2)3-ROo). The rate constant (~H T ) for intra-HT was determined to be 9.8 X lo5 s-l and independent of [BP-(CH2)3-ROH]. The deuterium isotope effect on intra-HT was examined by using BP-(CH&-ROD. The rate constant (~D T ) for intra-DT was determined to be 5.1 X lo5 s-l. In the presence of protons, the rate constant of intra-HT is enhanced proportional to the acid concentration though the value of r#Jm (=1.0) is independent of the acid concentration. The triplet molecule (BP-(CH2)s-3ROMe*) undergoes ionization only in the presence of protons (intra-pion) to yield a biradical molecule with >COH-and methoxynaphthalene cation radical (-ROMe'+) moieties (>C0H-(CH2)3-ROMeo+) with efficiencies (&I) of 0.3 for [H2S04] = 0.005 M and 1.0 for [H2S04] = 0.5 M in acetonitrilewater (4:l v/v) at 295 K. The rate constant for intra-pion increases with an increaseof the acid concentration. The mechanisms for intra-HT and intra-p-ion were interpreted by considering the intramolecular triplet exciplexes, 3(>CO-(CH2)3-ROH)* and 3(>CO-(CH2)3-ROMe)*, and the intramolecular protonated triplet exciplexes, 3(>+COH-(CH2)3-ROH)* and 3(>+COH-(CH2)3-ROMe)*, respectively. On the basis of the mechanism for intra-HT and intra-pion of the two chromophores linked with a propyrene chain, the structures of the triplet exciplex and protonated triplet exciplex are suggested to be sandwichlike with weak charge-transfer character.

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“…The results were explained on the basis of the intermediacy of the biradical 3, OH ~ ~..,jR2 3a:R1 = H, R2 = CHs 3b:RI=CHa, R2=H R1 3 Feit's results are compared with the photochemistry of 2-hexanone (which leads to 3a) in Table 1. The thermolyses of other aliphatic cyclobutanols have been examined by Stephenson "Yield of 2-hexanone based on the quantum yield of reversal (see k_, in reaction (1)), using data from reference 36 and the quantum yield of intersystem crossing reported by Encina and photochemistry of a number of related molecules were also examined, at~a Hornback *~ has been able to show that the biradical 8 can be generated by photolysis of 1,4-diphenyl-4-penten-l-ol 6 or 1,4-diphenybl-pentanone 7, where the biradical is produced via abstraction by the excited alkene.…”

Section: H Generation Of Biradicalsmentioning

confidence: 99%

Chemistry of the biradicals produced in the Norrish Type II reaction

Scaiano

Lissi

Encina

1978

Reviews of Chemical Intermediates

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Molecular photochemistry. L. Molecular photochemistry of alkanones in solution. .alpha.-Cleavage, hydrogen abstraction, cycloaddition, and sensitization reactions

Cited by 192 publications

References 19 publications

Photoisomerization of Bicyclo[3.1.1]heptan-2-ones in Methanol: Chemical Transformations of 'Verbanones'

Photoisomerization of Bicyclo[3.1.1]heptan-2-ones in Methanol: Chemical Transformations of 'Verbanones'

Laser flash photolysis studies on intramolecular hydrogen atom transfer of [(hydroxynaphthyl)propyl]benzophenone and intramolecular proton-induced electron transfer of [(methoxynaphthyl)propyl]benzophenone via triplet exciplexes

Chemistry of the biradicals produced in the Norrish Type II reaction

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