19270-10-1Relevant academic research and scientific papers
Thermal dissociation of acetophenone molecular ions activated by infrared radiation
Sena, Marcelo,Riveros, Jose M.
, p. 4384 - 4391 (1997)
The thermal dissociation of the molecular ions of acetophenone (C6H5COCH3?+ → C6H5CO+ + ?CH3) and acetophenone-d3 (C6H5COCD3?+ → C6H5CO+ + ?CD3) induced by broad band infrared radiation has been studied in the cell of an FT-ICR spectrometer. Rate constants in the range of 0.5-10 s-1 have been obtained for the system of ions exposed to a radiation source equivalent to blackbody temperatures between 1100 and 1600 K. The unimolecular dissociation is almost pressure independent in the 4 × 10-8 to 5 × 10-7 Torr range indicating that the most important mechanism is of a noncollisional nature. Activation energies obtained from Arrhenius-type plots yield 46.6 ± 2.0 kJ mol-1 for acetophenone and 44.9 ± 2.2 kJ mol-1 for acetophenone-d3. The dissociation process has been modeled by a Monte Carlo simulation and by numerical solution of the master equation of a process which takes into account interaction with the background radiation field through absorption and emission. These calculations reveal that meaningful activation energies can be obtained from these experiments even though the exact radiance viewed by the ions is not known. Solution of the master equation reveals that the experimental activation energies are consistent with a dissociation energy of 80.5 kJ mol-1 for the acetophenone molecular ion. This result is used to derive a heat of formation of 745 kJ mor-1 for the C6H5CO+ ion.
Generation and reactivity of the phenyl cation in cryogenic argon matrices: Monitoring the reactions with nitrogen and carbon monoxide directly by IR spectroscopy
Winkler, Michael,Sander, Wolfram
, p. 6357 - 6367 (2006)
The phenyl cation 1 has been prepared by co-deposition of iodobenzene 6 or bromobenzene 7 with a microwave-induced argon plasma and characterized by IR spectroscopy in cryogenic argon matrices. The cation can clearly be identified by its strongest absorpt
Synthesis of oxazoles by silver catalysed oxidative decarboxylation-cyclization of α-oxocarboxylates and isocyanides
Ma, Yiyang,Yan, Zhiyuan,Bian, Changliang,Li, Ke,Zhang, Xiaowen,Wang, Mengfan,Gao, Xinlong,Zhang, Heng,Lei, Aiwen
supporting information, p. 10524 - 10527 (2015/06/25)
A silver catalysed synthesis of oxazoles by the oxidative decarboxylation-cyclization of α-oxocarboxylates and isocyanides was developed. This method provided a novel strategy to construct oxazole rings compared to traditional methods. Mechanistic investigations such as operando IR, EPR and radical inhibition experiments were carefully done and confirmed the acyl cation and Ag(ii) as the intermediates in this transformation, and the involvement of a radical decarboxylative process.
Mass-Spectrometric Study on Ion-Molecule Reactions of CF3+ with Monosubstituted Benzenes Carrying a Carbonyl Group at Near-Thermal Energies
Tsuji, Masaharu,Aizawa, Masato,Nishimura, Yukio
, p. 1055 - 1063 (2007/10/03)
The gas-phase ion-molecule reactions of CF3+ with five monosubstituted benzenes carrying a carbonyl group (PhCOX: X=H, CH3, C2H5, OCH3, OC2H5) have been studied at near-thermal energies using an ion-beam apparatus. The major product channel for PhCHO, PhCOCH3, and PhCOOCH3 is electrophilic addition to the O-atom leading to initial adduct ions, which are 80.3 - 95.0% of the total product ions. Although no initial adduct ions are observed for PhCOC2H5 and PhCOOC2H5, major product ions are formed by electrophilic addition to the O-atom followed by dissociation and molecular eliminations. The reaction mechanism is discussed based on product ion distributions and semi-empirical calculations of the energies of intermediates and products. The results obtained are compared with reported-ion-cyclotron-resonance data for aliphatic carbonyl compounds.
Determination of the Enthalpies of Formation of C6H5CH2O·, p-CH3OC6H4CH2O·, and C6H5CHOH Radicals by Photoionization Mass Spectrometry
Ponomarev,Takhistov,Orlov
, p. 1774 - 1776 (2007/10/03)
The enthalpies of formation (kJ mol-1) of PhCH2O· (125), p-CH3OC6H4CH2O· (-37), and PhCHOH radicals (28) were determined from the energies of appearance of the corresponding fragment ions. The reliability of these data is confirmed by the coincidence of the experimental results with those calculated by the method of isodesmic reactions.
Reaction of Ammonia with Accelerated Benzoyl Ions under Multiple-collision Conditions in a Triple Quadrupole Instrument
White, Earl L.,Tabet, Jean-Claude,Bursey, Maurice M.
, p. 132 - 139 (2007/10/02)
The reaction of benzoyl ion with ammonia in multiple-collision conditions in the second quadrupole assembly of a triple quadrupole mass spectrometer at (laboratory) ion kinetic energies from 0 to 20 eV produced the even-electron ions +, m>+ (m=0,1) and + (n=0,1,2,3) and the odd-electron ions p>+. (p=0,1).Thermochemical information could not be obtained under multiple-collision conditions: both exotermic and endotermic reactions were observed, with no translational-energy onset measurable for the endothermic pr/cesses, nor decrease in the yield of the exothermic processes at high energies.The behaviour of cluster-ions intensities as pressure varied was qualitatively as expected.There are pressure and energy regions where spectra change little; if this feature were to be general, it would point to some utility for these conditions in qualitative analysis.
Dynamics of the Chemiionization Reaction of Antimony Pentafluoride
Russell, J. A.,Hershberger, J. F.,McAndrew, J. J.,Cross, R. J.,Saunders, M.
, p. 4494 - 4497 (2007/10/02)
Using crossed molecular beams we have measured the product angular and energy distributions for SbF5 + C6H5COCl -> SbF5Cl- + C6H5CO+ and for Sb2F10 + C6H5CH2Cl -> SbF6- + C7H7+ + SbF4Cl.In both cases the product distributions are symmetric about the center of mass which indicates that the reaction proceeds by way of a long-lived collision complex.However, in the first reaction, this symmetry appears to be broken at the highest energy studied so that the reaction becomes direct at higher energies.The first reaction has a threshold at roughly 2.9 eV.
Gas-Phase Chemiionization Reactions of Antimony Pentafluoride
Lee, L.,Russel, J.A.,Su, R.T.M.,Cross, R.J.,Saunders, M.
, p. 5031 - 5034 (2007/10/02)
Using crossed molecular beams, we have studied the reactions of SbF5 and its polymers with organic halides (RX).Monomer SbF5 reacts with some RX species to produce R(1+) + SbF5X(1-).Dimer reacts with a wider variety of RX species to produce R(1+) + SbF6(1-) + SbF4X.Unless R(1+) is particularly subject to cleavage, only the parent R(1+) is observed; this indicates that the product is formed with only a small amount of internal energy.
