Comparison of solvated electron reaction rates in water and ammonia

1977 ◽  
Vol 55 (11) ◽  
pp. 2159-2164 ◽  
Author(s):  
U. Schindewolf ◽  
P. Wünschel
Keyword(s):  
Rate Constant ◽  
Liquid Ammonia ◽  
Inorganic Ions ◽  
Reaction Rates ◽  
The Other ◽  
Solvated Electron ◽  
Aromatic Molecules ◽  
Rate Determining Step ◽  
Diffusion Controlled ◽  
Electrostatic Contribution

New and literature data of solvated electron reactions in ammonia with some inorganic ions and organic neutral molecules are compared with corresponding data in water. In ammonia only a few reactions with aromatic molecules are diffusion controlled and therefore faster than in water (k ≈ 1 × 1011 and 1 × 1010 M−1 s−1,respectively). After correcting for the electrostatic contribution to the rate constant of the other reactions it is concluded that in general the reactivity of the solvated electron in ammonia is appreciably lower, than in water. For the slow reactions of ammoniated electrons with acetonitrile and dimethylsulfoxide we find activation energies of 7 to 9 kcal/mol and activation volumes of −40 to −60 ml/mol. In these reactions it is suggested that the rate determining step is associated with the collapse of the large electron cavity in liquid ammonia.

Solvent structure effects on solvated electron reactions with ions in 2-butanol/water mixed solvents

1991 ◽  
Vol 69 (5) ◽  
pp. 884-892 ◽  
Author(s):  
Sedigallage A. Peiris ◽  
Gordon R. Freeman
Keyword(s):  
Rate Constant ◽  
Pure Water ◽  
Mixed Solvents ◽  
Reaction Rates ◽  
Bimolecular Reaction ◽  
Activation Energies ◽  
Solvated Electron ◽  
Polar Species ◽  
Water Solvent ◽  
Alcohol Water

The Smoluchowski–Debye–Stokes–Einstein equation for the rate constant k2 of a bimolecular reaction between charged or polar species[Formula: see text]was used to evaluate effects of bulk solvent properties on reaction rates of solvated electrons with [Formula: see text] and [Formula: see text] in 2-butanol/water mixed solvents. To explain detailed effects it was necessary to consider more specific behavior of the solvent. Rate constants k2, activation energies E2, and pre-exponential factors A2 of these reactions vary with the composition of 2-butanol/water mixtures. The values of E2 were in general similar to activation energies of ionic conductance EΛ0 of the solutions, except for much higher values of E2 of [Formula: see text] in alcohol-rich solvents and of [Formula: see text] in pure water solvent. The solvent apparently participates chemically in the [Formula: see text] reaction, and the [Formula: see text] reaction is multistep. Rate constant and conductance measurements of thallium acetate solutions in 2-butanol containing zero and 10 mol% water were complicated by the formation of ion clusters larger than pairs. Key words: alcohol/water mixed solvents, ions, reaction kinetics, solvated kinetics, solvated electron, solvent effects.

Reaction rates of electrons in liquid methanol and ethanol: effects of pressure

1976 ◽  
Vol 54 (8) ◽  
pp. 1177-1188 ◽  
Author(s):  
Gerald L. Bolton ◽  
Maurice G. Robinson ◽  
Gordon R. Freeman
Keyword(s):  
Rate Constant ◽  
Reaction Rates ◽  
Alcohol Molecule ◽  
High Concentration ◽  
Diffusion Controlled ◽  
Pure Alcohol ◽  
Wide Range ◽  
Solvent Density ◽  
Benzene Toluene ◽  
Experimental Values

The value of the rate constant k1 for the reaction e−solv → RO−solv + H, [1], at 295 K and 1 bar is ≤1.4 × 105 s−1 in methanol and ≤8 × 104 s−1 in ethanol. The respective volumes of activation averaged between 1 bar and 2 kbar are ΔV1≠ ≤ −21 and ≤ −22 cm3 mol−1. A high concentration of potassium hydroxide (1 M) or water (5 M) decreases the apparent value of k1 somewhat but has little or no effect on the value of ΔV1≠. The effect of pressure on the rate constant of e−solv + S → product, [2], was also measured for a series of solutes that displays a wide range of reactivity. Experimental values of ΔV2≠ depend on the relative contributions of the effects of solvent density on the reactant diffusion rates, the concentrations of the actual reacting species, and the relative energies of the reactant and intermediate states. For reactions whose rates are near the diffusion controlled limit, k2 ≈ 1010 M−1 s−1 in methanol and ethanol, the values of ΔV2≠ are positive and similar to those for the diffusion of simple ions. ΔV≠(e−solv diffusion) = 4 cm3 mol−1 in methanol and 6 cm3 mol−1 in ethanol. Cadmium chloride is apparently not completely dissociated in alcohols, and k(e−solv + CdCl2) < k(e−solv + CdCl+) < k(e−solv + Cd2+). For a series of compounds with lower rate constants there is a correlation between log k2 and ΔV2≠, the latter being negative for very low values of k2. The products of electron capture by benzene, toluene, ethyl acetate, and possibly acetonitrile appear to be stabilized by protonation: [Formula: see text] S−solv + ROH → SH + RO−slov, [4]. The results indicate that the decomposition of e−solv in a pure alcohol occurs by protonation of the electron site, e−solv + ROH → H + RO−slov, [4′], rather than by electron transfer to an alcohol molecule followed by decomposition of the anion.

Joining of Ti3SiC2 with Ti–6Al–4V Alloy

2002 ◽  
Vol 17 (1) ◽  
pp. 52-59 ◽  
Author(s):  
N.F. Gao ◽  
Y. Miyamoto
Keyword(s):  
Solid State ◽  
Rate Constant ◽  
Liquid State ◽  
Parabolic Rate Constant ◽  
Diffusion Path ◽  
Solid State Diffusion ◽  
Diffusion Controlled ◽  
State Diffusion ◽  
Rate Controlled ◽  
Higher Temperature

The joining of a Ti3SiC2 ceramic with a Ti–6Al–4V alloy was carried out at the temperature range of 1200–1400 °C for 15 min to 4 h in a vacuum. The total diffusion path of joining was determined to be Ti3SiC2/Ti5Si3Cx/Ti5Si3Cx + TiCx/TiCx/Ti. The reaction was rate controlled by the solid-state diffusion below 1350 °C and turned to the liquid-state diffusion controlled with a dramatic increase of parabolic rate constant Kp when the temperature exceeded 1350 °C. The TiCx tended to grow at the boundarywith the Ti–6Al–4V alloy at a higher temperature and longer holding time. TheTi3SiC2/Ti–6Al–4V joint is expected to be applied to implant materials.

Die Reaktionen chlorierter Äthylene mit hydratisierten Elektronen und OH-Radikalen in wäßriger Lösung / The Reaction of Chlorinated Ethylenes with Hydrated Electrons and OH-Radicals in Aqueous Solution

1971 ◽  
Vol 26 (11) ◽  
pp. 1108-1116 ◽  
Author(s):  
R. Köster ◽  
K.-D. Asmus
Keyword(s):  
Rate Constant ◽  
Oh Radicals ◽  
Capture Process ◽  
Chlorinated Ethylenes ◽  
Diffusion Controlled ◽  
Hydrated Electrons ◽  
Cl Atoms ◽  
Type Radical ◽  
Cl Atom ◽  
Steric Hinderance

The reactions of chlorinated ethylenes with hydrated electrons and OH radicals have been investigated by using the method of pulse radiolysis. In addition γ-ray experiments were carried out. The reduction of the solutes occurs via a dissoziation electron capture process. The rate constant for the reaction of eaq⊖ with the more chlorinated compounds is essentially diffusion controlled (k= (1 - 2×1010 l-mole-1 sec-1). Vinylchloride and 1,2-trans-dichloroethylene react more slowly. This can be related to the higher stability of the C-Cl bond in these compounds.Hydroxyl radicals add to the C=C double bond of the chlorinated ethylenes. The rate constant for the reaction with vinylchloride was determined to 7.1 × 109 1 · mole-1 sec-1, and decreases with increasing degree of chlorination of the ethylenes. This effect is explained by the decreasing electron density on the C-atoms and steric hinderance. The hydroxyl radical always adds to the C-atom carrying the smallest number of Cl-atoms. In its reaction with 1,2-dichloro-, trichloro- and tetrachloroethylene a radical is produced with an OH group and a Cl-atom on the same C-atom. It eliminates HCl to form a C=O bond with k>7 × 105 sec-1. The type radical produced in this reaction has an optical absorption in the near UV (ε265 nm = (1-3)×103 1 · mole-1 cm-1).The OH radical addition products of vinylchloride and 1,1-dichloroethylene do not eliminate HCl and have no absorption in the visible and near UV.

Diffusion‐controlled reactions: Upper bounds on the effective rate constant

1991 ◽  
Vol 94 (12) ◽  
pp. 7967-7971 ◽  
Author(s):  
J. Blawzdziewicz ◽  
G. Szamel ◽  
H. Van Beijeren
Keyword(s):  
Rate Constant ◽  
Effective Rate Constant ◽  
Effective Rate ◽  
Upper Bounds ◽  
Diffusion Controlled

scholarly journals Viscoadaptation controls intracellular reaction rates in response to heat and energy availability

2019 ◽  
Author(s):  
Laura Persson ◽  
Vardhaan S. Ambati ◽  
Onn Brandman
Keyword(s):  
Cellular Response ◽  
Reaction Rates ◽  
Acute Response ◽  
Cellular Environment ◽  
Diffusion Controlled ◽  
Intracellular Diffusion ◽  
Response To Temperature ◽  
And Diffusion ◽  
Tunable Property ◽  
Multiple Conditions

Summary/AbstractCells must precisely orchestrate thousands of reactions in both time and space. Yet reaction kinetics are highly dependent on uncontrollable environmental conditions such as temperature. Here, we report a novel mechanism by which budding yeast influence reaction rates through adjustment of intracellular viscosity. This “viscoadaptation” is achieved by production of two carbohydrates, trehalose and glycogen, which combine to create a more viscous cellular environment in which biomolecules retain solubility. We demonstrate that viscoadaptation functions as both an acute response to temperature increase as well as a homeostatic mechanism, allowing cells grown at temperatures spanning from 22°C to 40°C to maintain equivalent rates of intracellular diffusion and diffusion-controlled chemical reactions. Multiple conditions that lower ATP trigger viscoadaptation, suggesting that viscoadaptation may be a general cellular response to low energy. Viscoadaptation reveals viscosity to be a tunable property of cells through which they can regulate diffusion-controlled processes dynamically in response to a changing environment.

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