3170-69-2Relevant articles and documents
Cooperative Effect of Surface Sites on the Laser Flash Photolysis of 1,1-Diphenylacetone and 1,1,3,3-Tetraphenylacetone Adsorbed on Layered Clays. Generation of Radicals and Carbocations
Cozens, Frances L.,Garcia, Hermengildo,Gessner, F.,Scaiano, J. C.
, p. 8494 - 8497 (1994)
Laser flash photolysis of 1,1-diphenyl- and 1,1,3,3-tetraphenylacetone adsorbed onto a series of clays has been carried out under dry conditions.The photochemical behavior of the guests was investigated by using time-resolved diffuse reflectance techniques.Deposition of the organic compounds onto the solids was performed by slow removal of the solvent from dilute solutions at low temperature.Distinct transient spectra in the microsecond time domain were obtained for the guest-host composites.The formation of the diphenylmethyl radical (DPM.) was observed with montmorillonites SWy-1 (λmax = 310 nm) and STx-1 (λmax = 340 nm).The decay of DPM. on the bidimensional geometry of the layered clays was found to be much slower than within a tridimensional large-pore zeolite.By contrast, in the case of pillared Al13SWy-1 and Al13STx-1 clays, additional reflectance at 450 nm characteristic of the diphenylmethyl cation (DPM+) was present.This intermediate presumably arises from the cooperative interaction with the acid sites of the clay.These results show that these ketones are convenient probes to report on the chemical and topological properties of solid surfaces.
Kinetics of Intramolecular Alkyl Radical Attack on Sulfur in Disulfides and Thioesters
Beckwith, Athelstan L. J.,Duggan, Sandhya A. M.
, p. 1509 - 1518 (2007/10/02)
The 4-(alkyldithio)butyl radicals 8a and c, and the 4-(phenyldithio)butyl radical 8b, generated from the corresponding esters of N-hydroxypyridine-2(1H)-thione, undergo fast exo-cyclisation by SHi attack at sulfur.Similarly, the 5-(alkyldithio)pentyl radical 8d undergoes 1,6-ring formation.The rate constants for cyclisation were determined by photolysis of the radical precursors in the presence of appropriate thiols.Butyl and pentyl radicals bearing ω-acetylthio or ω-benzoylthio substituents also undergo ring closure but much more slowly.The kinetics of these intramolecular SH2 reactions are discussed and compared with those for the intermolecular attack of hexyl radicals on diphenyl disulfide and on dibutyl disulfide.
Generation, Thermodynamics, and Chemistry of the Diphenylcarbene Anion Radical (Ph2C.-)
McDonald, Richard N.,Gung, Wei Yi
, p. 7328 - 7334 (2007/10/02)
Dissociative electron attachment with Ph2C=N produced Ph2C.- (m/z 166).The reactions of Ph2C.- with potential proton donors of known gas-phase acidity were used to bracket PA(Ph2C.-) = 380 +/- 2 kcal mol-1 from which ΔHf0(Ph2C.-) = 81.8 +/- 2 kcal mol-1 was calculated.The reactions of Ph2C.- with CH3OH and C2H5OH proceeded with major and minor amounts, respectively, of a H2.+-transfer channel, forming Ph2CH2, RCHO, and an electron.The kinetic nucleophilicity of Ph2C.- in SN2 displacement reactions with CH3X and C2H5X molecules was shown to be medium, which requires a significant intrinsic barrier in these reaction.The reactions of Ph2C.- with various aldehydes, ketones, and esters were fast and established two principal product-forming channels: (1) H+ transfer if the neutral reactant contains activated C-H bonds and (2) carbonyl addition followed by radical β-fragmentation of one of the groups originally attached to the carbonyl carbon.The order for the ease of radical β-fragmentation in the tetrahedral intermediates was RO > alkyl >> H, and CO2CH3 > CH3.Since the reactions of Ph2C.- with the simple esters HCO2CH3 and CH3CO2CH3 were fast, it should now be possible to examine the reactions of carbonyl-containing organic molecules, which are expected to react slower than these esters and obtain their relative reactivities.
