scholarly journals Radiolysis of methylcyclohexane. IV. Effects of carbon tetrachloride and nitrous oxide in the vapor phase

1967 ◽  
Vol 45 (14) ◽  
pp. 1661-1668 ◽  
Author(s):  
W. J. Holtslander ◽  
G. R. Freeman
Keyword(s):  
Nitrous Oxide ◽  
Carbon Tetrachloride ◽  
Vapor Phase ◽  
Electron Affinity ◽  
Exothermic Reaction ◽  
Product Formation ◽  
Chain Termination ◽  
Chain Reaction ◽  
Positive Ions ◽  
Radiation Induced

There is a radiation-induced chain reaction in methylcyclohexane (MCH) – CCl4 mixtures in the vapor phase at 110° and 380 Torr. The chain-propagation products are chloroform and methylcyclohexylchloride (Gmax ≈ 40) and the chain-termination products are mainly methylcyclohexene (MC), bimethylcyclohexyl (C14), and hexachloroethane, depending on the composition of the mixture. At CCl4 concentrations < 1 mole%, HCl is formed mainly by reaction of Cl− with positive ions, e.g. Cl− + C7H14+ → HCl + C7H13. The value of the ratio G(MC)/G(C14) is 8 ± 1 in pure MCH and in the mixtures up to 44 mole% CCl4.There is a radiation-induced chain reaction in MCH–N2O mixtures in the vapor phase. At 110° and 380 Torr, G(N2) = 22, G(MC) = 16, and G(C14) = 1.6, independent of N2O concentration between 2 and 10 mole%. The G-values are independent of MCH pressure between 50 and 520 Torr. Product formation is inhibited by the addition of SF6 or DI. The half-life of the ion N2O− with respect to decomposition to N2 + O− is 10−4–10−3 s under these conditions. It is suggested that the mechanism contains the reactions [Formula: see text] [Formula: see text]Reaction [24] is slightly exothermic. Reaction [25] is exothermic if the electron affinity of N2O is greater than that of C7H13.

Radiation Induced Incorporation of CO in Pure and Aqueous Methanol

1994 ◽  
Vol 49 (4-5) ◽  
pp. 617-622
Author(s):  
Hak-Jin Jung ◽  
Nikola Getoff ◽  
Eberhard Lorbeer
Keyword(s):  
Oxalic Acid ◽  
Reaction Mechanisms ◽  
Elevated Pressure ◽  
Product Formation ◽  
Aqueous Methanol ◽  
Radiation Induced ◽  
Probable Reaction ◽  
Pure Methanol

Abstract Pure and aqueous methanol were used for radiation induced incorporation of CO at elevated pressure (up to 15 bar). The initial yields (Gi) of the main products in pure methanol under 15 bar CO and 1 bar N2O were found to be: Gi(formaldehyde) = 3.80 and Gi(glycolic aldehyde) = 2.0. For aqueous (10-2 mol · dm-3) methanol under 15 bar CO (dose: 0.557 kGy, pH = 2): the yields were G(formaldehyde) = 5.44, G(glycolic aldehyde) = 4.0 and G(oxalic acid) = 7.7. At pH = 7 the yields were essentially lower, namely: G(formaldehyde) = 3.2, G(glycolic aldehyde) = 2.0, G(formate) = 3.8 and G(oxalate) = 5.0. Probable reaction-mechanisms for the product formation are discussed.

scholarly journals Template-dependent inhibition of coronavirus RNA-dependent RNA polymerase by remdesivir reveals a second mechanism of action

2020 ◽  
Vol 295 (47) ◽  
pp. 16156-16165 ◽  
Author(s):  
Egor P. Tchesnokov ◽  
Calvin J. Gordon ◽  
Emma Woolner ◽  
Dana Kocinkova ◽  
Jason K. Perry ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Structural Model ◽  
Antiviral Agent ◽  
Product Formation ◽  
Chain Termination ◽  
Rna Dependent Rna Polymerase ◽  
Biologically Relevant ◽  
Direct Acting Antiviral ◽  
Dependent Inhibition ◽  
Direct Acting

Remdesivir (RDV) is a direct-acting antiviral agent that is used to treat patients with severe coronavirus disease 2019 (COVID-19). RDV targets the viral RNA-dependent RNA polymerase (RdRp) of severe acute respiratory syndrome coronavirus 2 (SARS–CoV-2). We have previously shown that incorporation of the active triphosphate form of RDV (RDV-TP) at position i causes delayed chain termination at position i + 3. Here we demonstrate that the S861G mutation in RdRp eliminates chain termination, which confirms the existence of a steric clash between Ser-861 and the incorporated RDV-TP. With WT RdRp, increasing concentrations of NTP pools cause a gradual decrease in termination and the resulting read-through increases full-length product formation. Hence, RDV residues could be embedded in copies of the first RNA strand that is later used as a template. We show that the efficiency of incorporation of the complementary UTP opposite template RDV is compromised, providing a second opportunity to inhibit replication. A structural model suggests that RDV, when serving as the template for the incoming UTP, is not properly positioned because of a significant clash with Ala-558. The adjacent Val-557 is in direct contact with the template base, and the V557L mutation is implicated in low-level resistance to RDV. We further show that the V557L mutation in RdRp lowers the nucleotide concentration required to bypass this template-dependent inhibition. The collective data provide strong evidence to show that template-dependent inhibition of SARS–CoV-2 RdRp by RDV is biologically relevant.

Absorption Spectrum and Chemical Reactions of Colloidal Cadmium in Aqueous Solution

1992 ◽  
Vol 272 ◽  
Author(s):  
M. Gutiérrez ◽  
A. Henglein
Keyword(s):  
Aqueous Solution ◽  
Nitrous Oxide ◽  
Absorption Spectrum ◽  
Carbon Tetrachloride ◽  
Chemical Reactions ◽  
Redox Reactions ◽  
Methyl Viologen ◽  
Narrow Band ◽  
Optical Data

ABSTRACTA radiolysis method is described to prepare isolated cadmium particles in aqueous solution. The spectrum of these particles (narrow band at 260nm) agrees with the spectrum calculated from the optical data of cadmium. Clusters of particles absorb at longer wavelengths. Redox reactions of the particles with methyl viologen, nitrous oxide and carbon tetrachloride were also investigated. It is shown that the absorption spectrum of the particles changes during these reactions as de-clustering takes place.

Radiolysis of ethyl iodide and carbon tetrachloride mixtures at 77°K

1968 ◽  
Vol 46 (10) ◽  
pp. 1625-1632 ◽  
Author(s):  
R. M. Leblanc ◽  
F. C. Thyrion ◽  
J. A. Herman
Keyword(s):  
Electron Spin Resonance ◽  
Charge Transfer ◽  
Carbon Tetrachloride ◽  
Electron Spin ◽  
Ethyl Iodide ◽  
Ion Molecule Reactions ◽  
Positive Ions ◽  
Spin Resonance ◽  
Γ Rays ◽  
The Difference

The radical yields of C2H5• and CCl3• observed by electron spin resonance of CCl4 + C2H5I mixtures irradiated by γ rays at 77°K are compared with yields of HCl, I2, and HI measured after thawing. The dissociative capture of thermalized electrons by CCl4 is extremely effective and accounts for most of the observed radicals. The difference between yields of HCl and CCl3• results from charge transfer from C2H5I+ to CCl3•. The formation of iodine proceeds both from neutralization processes of Cl− ions with positive ions formed from C2H5I, and from ion–molecule reactions.

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