Ion-molecule reactions in acetone-water mixtures

1966 ◽  
Vol 19 (1) ◽  
pp. 59 ◽  
Author(s):  
Souza BC de ◽  
JH Green
Keyword(s):  
Hydrogen Atom ◽  
Proton Transfer ◽  
Transfer Process ◽  
Hydrogen Atom Transfer ◽  
Mass Spectrometric ◽  
Transfer Mechanism ◽  
Atom Transfer ◽  
Ion Molecule Reactions ◽  
Acetone Water

Mass-spectrometric studies of ion-molecule reactions in acetone-water mixtures at 70 eV and 20 eV electron energies are described. The results provide evidence in favour of the proton transfer mechanism rather than for a hydrogen atom transfer process for the production of M + 1 ions.

Carbonylative Coupling of Simple Alkanes and Alkenes Enabled by Organic Photoredox Catalysis

2021 ◽  
Author(s):  
Ling Chen ◽  
Jing Hou ◽  
Ming Zheng ◽  
Le-Wu Zhan ◽  
Wan-Ying Tang ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Visible Light ◽  
Transfer Process ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Photoredox Catalysis ◽  
Visible Light Driven

A visible-light-driven direct carbonylative coupling of simple alkanes and alkenes via the combination of the hydrogen atom transfer process and photoredox catalysis has been demonstrated. Employing the N-alkoxyazinium salt as...

Radical Catalyzed Debromination of Bromo-Alkanes by Formate in Aqueous Solutions via a Hydrogen Atom Transfer Mechanism.

ChemInform ◽  
2004 ◽  
Vol 35 (20) ◽  
Author(s):  
Elisabetha Shandalov ◽  
Israel Zilbermann ◽  
Eric Maimon ◽  
Yeoshua Nahmani ◽  
Haim Cohen ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Aqueous Solutions ◽  
Hydrogen Atom Transfer ◽  
Transfer Mechanism ◽  
Atom Transfer

Microsolvation, hydrogen bond dynamics and excited state hydrogen atom transfer mechanism of 2′,4′-dihydroxychalcone

2020 ◽  
Vol 739 ◽  
pp. 137030
Author(s):  
Yelechakanahalli Lingaraju Ramu ◽  
Kandigowda Jagadeesha ◽  
Tavarekere Shivalingaswamy ◽  
Mariyappa Ramegowda
Keyword(s):  
Hydrogen Bond ◽  
Excited State ◽  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Transfer Mechanism ◽  
Atom Transfer ◽  
Hydrogen Bond Dynamics

scholarly journals Carboxylate breaks the arene C–H bond via a hydrogen-atom-transfer mechanism in electrochemical cobalt catalysis

2020 ◽  
Vol 11 (22) ◽  
pp. 5790-5796
Author(s):  
Xin-Ran Chen ◽  
Shuo-Qing Zhang ◽  
Tjark H. Meyer ◽  
Chun-Hui Yang ◽  
Qin-Hao Zhang ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Transfer Mechanism ◽  
Atom Transfer

A formal Co(iv) intermediate in electrochemical cobalt-catalyzed C–H oxygenation allows pivalate to break the arene C–H bond via a hydrogen-atom-transfer mechanism.

The water–boryl radical as a proton-coupled electron transfer reagent for carbon dioxide, formic acid, and formaldehyde — Theoretical approach

2013 ◽  
Vol 91 (2) ◽  
pp. 155-168
Author(s):  
Waled Tantawy ◽  
Ahmed Hashem ◽  
Nabil Yousif ◽  
Eman Flefel
Keyword(s):  
Carbon Dioxide ◽  
Hydrogen Bond ◽  
Electron Transfer ◽  
Hydrogen Atom ◽  
Transfer Process ◽  
Carbonyl Compounds ◽  
Hydrogen Atom Transfer ◽  
Transfer Reactions ◽  
Atom Transfer ◽  
Proton Coupled Electron Transfer

The thermochemistry of the hydrogen atom transfer reactions from the H2O–BX2 radical system (X = H, CH3, NH2, OH, F) to carbon dioxide, formic acid, and (or) formaldehyde, which produce hydroxyformyl, dihydroxymethyl, and hydroxymethyl radicals, respectively, were investigated theoretically at ROMP2/6–311+G(3DF,2P)//UB3LYP/6–31G(D) and UG3(MP2)-RAD levels of theory. Surprisingly, in the cases of a strong Lewis acid (X = H, CH3, F), the spin transfer process from the water–boryl radical to the carbonyl compounds was barrier-free and associated with a dramatic reduction in the B–H bond dissociation energy (BDE) relative to that of isolated water–borane complexes. Examining the coordinates of these reactions revealed that the entire hydrogen atom transfer process is governed by the proton-coupled electron transfer (PCET) mechanism. Hence, the elucidated mechanism has been applied in the cases of weak Lewis acids (X = NH2, OH), and the variation in the accompanied activation energy was attributed to the stereoelectronic effect interplaying in CO2 and HCOOH compared with HCHO. We ascribed the overall mechanism as a SA-induced five-center cyclic PCET, in which the proton transfers across the so-called complexation-induced hydrogen bond (CIHB) channel, while the SOMOB–LUMOC=O′ interaction is responsible for the electron migration process. Owing to previous reports that interrelate the hydrogen-bonding and the rate of proton-coupled electron-transfer reactions, we postulated that “the rate of the PCET reaction is expected to be promoted by the covalency of the hydrogen bond, and any factor that enhances this covalency could be considered an activator of the PCET process.” This postulate could be considered a good rationale for the lack of a barrier associated with the hydrogen atom transfer from the water-boryl radical system to the carbonyl compounds. Light has been shed on the water–boryl radical reagent from the thermodynamic perspective.

Selected-ion flow tube studies of reactions of the radical cation (HC3N)+• in the interstellar chemical synthesis of cyanoacetylene

1986 ◽  
Vol 64 (2) ◽  
pp. 399-403 ◽  
Author(s):  
A. Fox ◽  
A. B. Raksit ◽  
S. Dheandhanoo ◽  
D. K. Bohme
Keyword(s):  
Hydrogen Atom ◽  
Proton Transfer ◽  
Radical Cation ◽  
Covalent Bond ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Flow Tube ◽  
Ion Flow ◽  
Wide Range ◽  
Selected Ion Flow Tube

The radical cation (HC3N)+• was produced in a Selected-Ion Flow Tube (SIFT) apparatus from cyanoacetylene by electron impact and reacted at room temperature in helium buffer gas with a selection of molecules including H2, CO, HCN, CH4, H2O, O2, HC3N, C2H2, OCS, C2H4, and C4H2. The observed reactions exhibited a wide range of reactivity and a variety of pathways including charge transfer, hydrogen atom transfer, proton transfer, and association. Association reactions were observed with CO, O2, HCN, and HC3N. With the latter two molecules association was observed to proceed close to the collision limit, which is suggestive of covalent bond formation perhaps involving azine-like N—N bonds. For HC3N an equally rapid association has been observed by Buckley etal. with ICR (Ion Cyclotron Resonance) measurements at low pressures and this is suggestive of radiative association. The hydrogen atom transfer reaction of ionized cyanoacetylene with H2 is slow while similar reactions with CH4 and H2O are fast. The reaction with CO fails to transfer a proton. These results have implications for synthetic schemes for cyanoacetylene as proposed in recent models of the chemistry of interstellar gas clouds. Proton transfer was also observed to be curiously unfavourable with all other molecules having a proton affinity higher than (C3N)•. Also, hydrogen-atom transfer was inefficient with the polar molecules HCN and HC3N. These results suggest that interactions at close separations may lead to preferential alignment of the reacting ion and molecule which is not suited for proton transfer or hydrogen atom transfer.

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