1889-67-4Relevant articles and documents
Solid-state photodecarbonylation of diphenylcyclopropenone: A quantum chain process made possible by ultrafast energy transfer
Kuzmanich, Gregory,Natarajan, Arunkumar,Chin, Khin K.,Veerman, Marcel,Mortko, Christopher J.,Garcia-Garibay, Miguel A.
, p. 1140 - 1141 (2008)
It has been reported that electronic excitation of diphenylcyclopropenone (DPCP) into the second excited state (S2) results in an adiabatic ring-opening process within 200 fs to give an excited product with a lifetime of ca. 8 ps in S2. Knowing that energy transfer in crystals may occur within 1-2 ps, we recognized that the conditions could be right for a quantum chain process with the excited-state product sensitizing a neighboring ground-state reactant to set up a domino effect. In agreement with that, we discovered that excitation or macroscopic crystals result in a remarkably efficient reaction to give diphenylacetylene as a polycrystalline powder by a process that releases a great deal of mechanical energy. By taking advantage of nanocrystalline suspensions and using dicumyl ketone as an internal actinometer and after accounting for differences in absorbance at the irradiation wavelength, we were able to establish that the quantum yield of the reaction for DPCP was ΦDPCP = 3.30 ± 0.35, which is well above unity and consistent with a remarkable quantum chain process. Copyright
Photo-Fries reaction in water made selective with a capsule
Kaanumalle, Lakshmi S.,Gibb, Corinne L. D.,Gibb, Bruce C.,Ramamurthy
, p. 236 - 238 (2007)
The water soluble capsule formed by a deep cavity cavitand with eight carboxylic acid groups controls product distribution during photo-Fries rearrangement of naphthyl esters in water by restricting the mobility of primary singlet radical pair. The Royal Society of Chemistry.
Large-scale photochemical reactions of nanocrystalline suspensions: A promising green chemistry method
Veerman, Marcel,Resendiz, Marino J. E.,Garcia-Garibay, Miguel A.
, p. 2615 - 2617 (2006)
Photochemical reactions in the solid state can be scaled up from a few milligrams to 10 grams by using colloidal suspensions of a photoactive molecular crystal prepared by the solvent shift method. Pure products are recovered by filtration, and the use of H2O as a suspension medium makes this method a very attractive one from a green chemistry perspective. Using the photodecarbonylation of dicumyl ketone (DCK) as a test system, we show that reaction efficiencies in colloidal suspensions rival those observed in solution.
Enhanced cage effects in supercritical fluid solvents. The behavior of diffusive and geminate caged-pairs in supercritical carbon dioxide
Tanko,Pacut
, p. 5703 - 5709 (2001)
The behavior of geminate and diffusive radical caged-pairs arising from the photolysis of dicumyl ketone in conventional and supercritical carbon dioxide (SC-CO2) solvents has been examined. The results suggest that locally enhanced solvent density about a solute (solvent/solute clustering) can lead to an enhanced cage effect near the critical pressure in supercritical fluid solvents. This enhanced cage effect is similar in magnitude for both diffusive and geminate caged-pairs.
Oxidation of Isopropylbenzene by Iron Tetraphenylporphyrin: Evidence for the Interaction of the Cumyl Radical with Oxygen Donors
Baciocchi, Enrico,d'Acunzo, Francesca,Galli, Carlo,Ioele, Marcella
, p. 429 - 430 (1995)
Evidence is presented for an unprecedented oxygen transfer from oxygen donors to a cumyl radical in the oxidation of isopropylbenzene catalysed by tetraphenyl metalloporphyrins.
Synthesis and Thermal Decomposition of Di-t-Butyl Peroxydicarbonate
Komai, Takeshi,Matsuyama, Kazuo
, p. 2207 - 2211 (1985)
Di-t-butyl peroxydicarbonate(DBPD) has been synthesized in a novel route and thermally decomposed at 40-70 deg C.The decomposition exhibits first-order kinetics and the values of ΔH* and ΔS* are 122 kJ mol-1 and 46 J K-1 mol-1, respectively. 2-Methyl-2-propanol is obtained quantitatively as a decomposition product and the rates are a little dependant on the viscosities of solvents, normal alkanes.The mechanism that involves the initial scission of the O-O bond is discussed and the values of the rates and the activation parameters of DBPD are compared withthose of diacetyl peroxide and dibenzoyl peroxide.
Pressure Effects on Azocumene Decomposition Rates, Efficiencies of Radical Production, and Semibenzene Dimers
Neuman, Robert C.,Amrich, Michael J.
, p. 4629 - 4636 (1980)
Rates of thermal decomposition of azocumene (1a) and p,p'-dimethylazocumene (1b) in cumene or chlorobenzene are decreased by pressure with decomposition activation volumes of +5 cm3/mol (1a,cumene), +4.3 cm3/mol (1a,chlorobenzene) and +4.6 cm3/mol (1b,cumene).Efficiencies (f) of radical production, with di-tert-butyl nitroxide (DBNO) or thiophenol as scavengers, decrease with pressure; however, the pressure dependence of f with DBNO is anomalous.This is explained by the formation of semibenzene dimers as cage products, which subsequently decompose to give cumyl radicals.The corresponding α-ortho semibenzene dimers of cumyl radicals are formed from both 1a and 1b.The α-para semibenzene dimer from decomposition of 1a in chlorobenzene appears to rearrange to give p-cumylcumene.No such rearrangements appears to occur from the α-ortho dimers nor is it likely that any α-para dimer is formed from 1b decomposition.An apparent activation volume for thermal decomposition of the α-ortho semibenzene dimer in cyclohexane at 20 deg C is ca. +6 cm3/mol.Pressure favors disproportionation over coupling for geminate cumyl radicals.
Synthesis of Sterically Hindered α-Hydroxycarbonyls through Radical-Radical Coupling
Ota, Kenji,Nagao, Kazunori,Ohmiya, Hirohisa
supporting information, p. 4420 - 4425 (2021/05/26)
We describe a synthetic approach to sterically hindered α-hydroxy carbonyl compounds through radical-radical coupling. An organic photoredox catalysis reaction converts an aliphatic carboxylic acid and α-ketocarbonyl to a transient alkyl radical and a persistent ketyl radical, respectively, which couple selectively based on the persistent radical effect. This protocol allows the use of primary, secondary, and tertiary aliphatic carboxylic acids to introduce various alkyl substituents onto ketone moieties of α-ketocarbonyls under mild reaction conditions.
Phenylene-bridged bis(benzimidazolium) (BBIm2+): a dicationic organic photoredox catalyst
Kodama, Takuya,Kubo, Maiko,Shinji, Wataru,Ohkubo, Kei,Tobisu, Mamoru
, p. 12109 - 12117 (2020/11/27)
A dicationic photoredox catalyst composed of phenylene-bridged bis(benzimidazolium) (BBIm2+) was designed, synthesised and demonstrated to promote the photochemical decarboxylative hydroxylation and dimerisation of carboxylic acids. The catalytic activity of BBIm2+ was higher than that for a monocation analogue, suggesting that the dicationic nature of BBIm2+ plays a key role in these decarboxylative reactions. The rate constant for the decay of the triplet-triplet absorption of the excited BBIm2+ increased with increasing concentration of the carboxylate anion with a saturated dependence, suggesting that photoinduced electron transfer occurs within the ion pair complex composed of the triplet excited state of BBIm2+ and a carboxylate anion.
