16805-85-9Relevant articles and documents
1,1-Diphenylethylene adsorbed onto acid zeolites: Nature of the blue (605-nm) species
Fornes, Vicente,Garcia, Hermenegildo,Jovanovic, Slobodan,Marti, Vicente
, p. 4715 - 4726 (1997)
Diffuse reflectance spectra of HY (Si/Al 15) and Hβ (Si/Al 13) zeolites after adsorption of 1,1-diphenylethylene (DPE) show an intense 605-nm absorption band characteristic of an elusive blue species observed a long time ago for DPE-silica-alumina solids. This blue species was wrongly attributed to the corresponding DPE+. radical cation or a complex of DPE with Lewis sites of these solids. In our case, EPR spectra of DPE samples adsorbed on HY and Hβ zeolites indicate that the spin population of these samples is too low (15 spin · g-1) to contain significant amounts of any paramagnetic species. In addition, IR spectra of the organic material incorporated within HY and Hβ is very similar to those of some DPE dimers. Product studies after solid-liquid extraction of zeolites and silica-alumina in which DPE has been adsorbed also show the formation of the corresponding dimers derived from the acid-catalyzed mechanism. Variable amounts of oxidation products are also formed when the adsorption is carried out in the open air. In addition, 13C-NMR spectra in solution of blue samples generated by treatment of DPE with sulfuric acid in dimethyl sulfate also indicate the presence of the same dimer distribution and the absence of detectable low-field signals that could be attributed to any carbenium ion. With these data, it is clear that in spite of the intense color developed in these samples, the bulk of the organic material adsorbed on the zeolites does not correspond to any intermediate, but to dimers. Semiempirical ROHF calculations using the ZINDO program provide some support to the possibility that the blue color could be due to 1,1,3,3-tetraphenyl-1-butylium cation, the reaction intermediate involved in the DPE dimerization mechanism.
Straightforward formation of carbocations from tertiary carboxylic acids: Via CO release at room temperature
Bartalucci, Niccolò,Pampaloni, Guido,Marchetti, Fabio,Bortoluzzi, Marco,Zacchini, Stefano
supporting information, p. 1574 - 1577 (2019/04/02)
We report an unprecedented mode of reactivity of carboxylic acids. A series of tertiary carboxylic acids, containing at least one phenyl α-substituent, undergo loss of carbon monoxide at room temperature (295 K), by a one pot reaction with 0.5-1 molar equivalents of WCl6 in dichloromethane. A plausible mechanism for the Ph3CCO2H/WCl6 reaction, leading to [CPh3][WOCl5] and Ph3CCl, is proposed on the basis of DFT calculations. The analogous reactions involving CEt(Ph)2CO2H, CMe(Ph)2CO2H and CMe2(Ph)CO2H selectively afforded stable hydrocarbons (alkene or indene, depending on the case), apparently resulting from the rearrangement of elusive tertiary carbocations.
Lifetimes and UV-visible absorption spectra of benzyl, phenethyl, and cumyl carbocations and corresponding vinyl cations. A laser flash photolysis study
Cozens, Frances L.,Kanagasabapathy,McClelland, Robert A.,Steenken, Steen
, p. 2069 - 2082 (2007/10/03)
Benzyl (4-MeO, 4-Me, and 4-methoxy-1-naphthylmethyl), phenethyl (4- Me2N, 4-MeO, 3,4-(MeO)2, 4-Me, 3-Me, 4-F, 3-MeO, 2,6-Me2, parent, and 4- methoxy-1-naphthylethyl) and cumyl (4-Me2N, 4-MeO, 4-Me, parent) cations have been studied by laser flash photolysis (LFP) in 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). In most cases styrene or α-methylstyrene precursors were employed for the phenethyl and cumyl ions, the intermediate being obtained by solvent protonation of the excited state. Benzyl cations were generated by photoheterolysis of trimethylammonium and chloride precursors. While a 4-MeO substituent provides sufficient stabilization to permit observation of cations in TFE, cations with less stabilizing substituents usually require the less nucleophilic HFIP. Even in this solvent, the parent benzyl cation is too short-lived (lifetime 6H4C+(R)-CH3 (R = Me, Et, i-Pr, t-Bu, cyclopropyl, C6H5, 4-MeOC6H4) were generated in TFE via the photoprotonation route. The alkyl series shows that steric effects are important in the decay reaction. The cation with R = cyclopropyl is a factor of 1.5 less reactive than the cation where R = phenyl. Several vinyl cations have also been generated by photoprotonation of phenylacetylenes. ArC+=CH2 has a reactivity very similar to that of its analog ArC+H-CH3, the vinyl cation being slightly (factors of 2-5) shorter-lived. For the various series of cations, including vinyl, substituents in the aryl ring have a consistent effect on the κ(max), a shift to higher wavelength relative to hydrogen of 15 nm for 4-Me, 30 nm for 4-MeO, and 50 nm for 4-Me2N.
