Search results for "Homolysis"
showing 6 items of 6 documents
Unravelling the kinetics and molecular mechanism of the degenerate Cope rearrangement of bullvalene
2020
The kinetics and molecular mechanism of the gas phase degenerate Cope rearrangement (DCR) of bullvalene have been investigated by applying quantum mechanical calculations. Highly accurate energies (CBS-QB3 and CBS-APNO) and RRKM calculations were employed to study the kinetics and ‘fall-off’ behavior. It was found that the DCR of bullvalene (C3v) occurs through a bishomoaromatic transition structure (C2v) with an energy barrier of ∼49 kJ mol−1. The calculated activation energy and enthalpy were in good agreement with the available values in the literature, but lower than those of common Cope rearrangement; this result is related to the high stabilization energy due to the interaction of the…
The Taming of Redox‐Labile Phosphidotitanocene Cations
2019
International audience; Tame d0 phosphidotitanocene cations stabilized with a pendant tertiary phosphane arm are reported. These compounds were obtained by one-electron oxidation of d1 precursors with [Cp2Fe][BPh4]. The electronic structure of these compounds was studied experimentally (EPR, UV/Vis, and NMR spectroscopy, X-ray diffraction analysis) and through DFT calculations. The theoretical analysis of the bonding situation by using the electron localization function (ELF) shows the presence of π-interactions between the phosphido ligand and Ti in the d0 complexes, whereas dπ–pπ repulsion prevents such interactions in the d1 complexes. In addition, CH–π interactions were observed in seve…
Ultrasound-assisted MnO2 catalyzed homolysis of peracetic acid for phenol degradation: The assessment of process chemistry and kinetics
2013
Abstract The combination of peracetic acid (PAA) and heterogeneous catalyst (MnO 2 ) was used for the degradation of phenol in an aqueous solution in the presence of ultrasound irradiation (US). As a relevant source of free radicals (e.g. OH), peracetic acid was comprehensively studied by means of electron spin resonance (ESR) spin trapping (ST) techniques with the subsequent identification of free radicals by simulation based fitting (SBF) technique. The radical reaction mechanism, where hydroxyl radical was a primary product of O O bond rupture of PAA, was established taking into account radical reactions, occurring during sonolysis. The potential barriers and the reaction heat were deter…
Anchimer beschleunigte Homolysen, V. Thermische und Fluoridionen‐katalysierte Umlagerungen von Benzyl)‐[9‐(trimethylgermyl)‐9‐fluorenyl]‐ether
1980
Anchimerically Enhanced Homolyses, V. Fluoride Ion Catalysed Rearrangements of Benzyl 9-(Trimethylgermyl)-9-fluorenyl Ether The thermal rearrangement (homolysis) of the germanium compound 1d into 4d is considerably slower than that of the analogous Si compound 1c. Thus, a correlation is suggested between the velocity of the rearrangement and the strength of the new bond to oxygen. The rearrangement 1d4d is also induced by fluoride ions at room temperature.
Coordinatively Unsaturated Amidotitanocene Cations with Inverted σ and π Bond Strengths: Controlled Release of Aminyl Radicals and Hydrogenation/Dehy…
2021
Cationic amidotitanocene complexes [Cp2 Ti(NPhAr)][B(C6 F5 )4 ] (Cp=η5 -C5 H5 ; Ar=phenyl (1 a), p-tolyl (1 b), p-anisyl (1 c)) were isolated. The bonding situation was studied by DFT (Density Functional Theory) using EDA-NOCV (Energy Decomposition Analysis with Natural Orbitals for Chemical Valence). The polar Ti-N bond in 1 a-c features an unusual inversion of σ and π bond strengths responsible for the balance between stability and reactivity in these coordinatively unsaturated species. In solution, 1 a-c undergo photolytic Ti-N cleavage to release Ti(III) species and aminyl radicals ⋅NPhAr. Reaction of 1 b with H3 BNHMe2 results in fast homolytic Ti-N cleavage to give [Cp2 Ti(H3 BNHMe2 )…
A novel photochemical 1,4-acyl migration in enol esters. The photolysis of enol acetates of 3-phenylpropiophenones
1987
Abstract Photolysis of the enol acetates 1a,b gives the 1,4-diketones 4a,b by a mechanism involving a primary homolytic carbonyl—oxygen bond cleavage, followed by 1,2-hydrogen shift and in cage recombination.