Trajectory study of dissociation reactions. Br2 in Ar at 3500 K

1977 ◽  
Vol 55 (3) ◽  
pp. 380-382 ◽  
Author(s):  
D. T. Chang ◽  
George Burns
Keyword(s):  
High Temperatures ◽  
Rate Constant ◽  
Rate Coefficient ◽  
Dissociation Rate ◽  
Experimental Results ◽  
Dissociation Rate Constant ◽  
Trajectory Calculations ◽  
Order Of Magnitude ◽  
Nonequilibrium Effects ◽  
The One

Dissociation of Br2 in Ar was studied at 3500 K using classical 3-D trajectory technique, and compared with earlier trajectory calculations. Some of the assumptions used previously were eliminated, while others were studied in some detail. The one-way flux, equilibrium rate coefficient, obtained from over 8400 trajectories, was found to be over an order of magnitude larger than the experimental rate constant. This was taken as an indication that at high temperatures the nonequilibrium effects are important in dissociation reactions. In order to understand these effects better, additional calculations using an improved set of assumptions were performed. The calculated dissociation rate constant for Br2 + Ar → 2Br + Ar reaction, which accounted for nonequilibrium effects, agrees reasonably well with experimental results.

scholarly journals Protein-ligand dissociation rate constant from all-atom simulation

2021 ◽  
Author(s):  
Ekaterina Maximova ◽  
Eugene Postnikov ◽  
Anastasia Lavrova ◽  
Vladimir Farafonov ◽  
Dmitry Nerukh
Keyword(s):  
Molecular Dynamics ◽  
Rate Constant ◽  
Md Simulations ◽  
Dissociation Rate ◽  
Dissociation Rate Constant ◽  
Zero Force ◽  
Ligand Dissociation ◽  
Random Acceleration

Abstract Dissociation of a ligand isoniazid from a protein catalase was investigated using all-atom Molecular Dynamics (MD) simulations. Random Acceleration MD (τ-RAMD) was used where a random artificial force applied to the ligand facilitates its dissociation. We have suggested an approach to extrapolate such obtained dissociation times to the zero-force limit that was never attempted before, thus allowing direct comparison with experimentally measured values. We have found that our calculated dissociation time was equal to 36.1 seconds with statistically significant values distributed in the interval 0.2-72.0 s, that quantitatively matches the experimental value of 50 ± 8 seconds despite the extrapolation over nine orders of magnitude in time.

scholarly journals A sequence-specific threading tetra-intercalator with an extremely slow dissociation rate constant

2011 ◽  
Vol 3 (11) ◽  
pp. 875-881 ◽  
Author(s):  
Garen G. Holman ◽  
Maha Zewail-Foote ◽  
Amy Rhoden Smith ◽  
Kenneth A. Johnson ◽  
Brent L. Iverson
Keyword(s):  
Rate Constant ◽  
Dissociation Rate ◽  
Dissociation Rate Constant ◽  
Slow Dissociation

scholarly journals Reversibility in radionuclide/bentonite bulk and colloidal ternary systems

2015 ◽  
Vol 79 (6) ◽  
pp. 1307-1315 ◽  
Author(s):  
Nick Sherriff ◽  
Ragiab Issa ◽  
Katherine Morris ◽  
Francis Livens ◽  
Sarah Heath ◽  
...  
Keyword(s):  
Rate Constant ◽  
Ethylenediaminetetraacetic Acid ◽  
Average Rate ◽  
Ternary Systems ◽  
Dissociation Rate ◽  
Convincing Evidence ◽  
Dissociation Rate Constant ◽  
Stage Process ◽  
Slow Dissociation ◽  
The Eu

AbstractTernary systems of 152Eu(III), bulk bentonite and ethylenediaminetetraacetic acid (EDTA) ([Eu] = 7.9 × 10–10 M; pH = 6.0–7.0) have been studied. Without EDTA, there was slow uptake in a two-stage process, with initial rapid sorption of Eu(III) (96%), followed by slower uptake of a much smaller fraction (3.0% over a period of one month). The reversibility of Eu(III) binding was tested by allowing Eu(III) to sorb to bentonite for 1–322 days. EDTA was added to the pre-equilibrated Eu bentonite systems at 0.01 M, a concentration that was sufficient to suppress sorption in a system where EDTA was present prior to the contact of Eu(III) with bentonite. A fraction of the Eu was released instantaneously (30–50%), but a significant amount remained bound. With time, the amount of Eu(III) retained by the bentonite reduced, with a slow fraction dissociation rate constant of approximately 4.3 × 10–8 s–1 (values in the range 2.2 × 10–8 – 1.0 × 10–7 s–1) for pre-equilibration times ≥7 days. Eventually, the amount of Eu(III) remaining bound to the bentonite was within error of that when EDTA was present prior to contact (4.5% ± 0.6), although in systems with pre-equilibration times >100 days, full release took up to 500 days. Europium interactions with colloidal bentonite were also studied, and the dissociation rate constant measured by a resin competition method. For the colloids, more Eu was found in the slowly dissociating fraction (60–70%), but the first-order dissociation rate constant was faster, with an average rate constant of 8.8 × 10–7 s–1 and a range of 7.7 × 10–7 –9.5 × 10–7 s–1. For both bulk and colloidal bentonite, although slow dissociation was observed for Eu(III), there was no convincing evidence for 'irreversible' binding.

scholarly journals Radical Chain Monoalkylation of Pyridines

2021 ◽  
Author(s):  
Samuel Rieder ◽  
Camilo Meléndez ◽  
Kleni Mulliri ◽  
Philippe Renaud
Keyword(s):  
Rate Constant ◽  
Iodine Atom ◽  
Radical Chain ◽  
Enol Ethers ◽  
Alkyl Radicals ◽  
Reaction Proceeds ◽  
Order Of Magnitude ◽  
Enol Esters ◽  
The One ◽  
Neutral Conditions

<p>The monoalkylation of N-methoxypyridinium salts with alkyl radicals generated from alkenes (via hydroboration with catecholborane), alkyl iodides (via iodine atom transfer) and xanthates is reported. The reaction proceeds under neutral conditions since no acid is needed to activate the heterocycle and does not require the use of an external oxidant. A rate constant for the addition of a primary radical to N-methoxylepidinium >107 M–1 s–1 was experimentally determined. This rate constant is more than one order of magnitude larger than the one measured for the addition of primary alkyl radical to protonated lepidine demonstrating the remarkable reactivity of methoxypyridinium salts towards radicals. The reaction could be extended to a three component carbopyridinylation of electron rich alkenes including enol esters, enol ethers and enamides.</p>

Protein–Ligand Dissociation Rate Constant from All-Atom Simulation

2021 ◽  
pp. 10631-10636
Author(s):  
Ekaterina Maximova ◽  
Eugene B. Postnikov ◽  
Anastasia I. Lavrova ◽  
Vladimir Farafonov ◽  
Dmitry Nerukh
Keyword(s):  
Rate Constant ◽  
Dissociation Rate ◽  
Dissociation Rate Constant ◽  
Ligand Dissociation
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