Solvent effects on the reactivity of solvated electrons with organic solutes in methanol/water and ethanol/water mixed solvents

1990 ◽  
Vol 94 (1) ◽  
pp. 302-308 ◽  
Author(s):  
Charles C. Lai ◽  
Gordon R. Freeman
Keyword(s):  
Solvent Effects ◽  
Mixed Solvents ◽  
Organic Solutes ◽  
Solvated Electrons

Solvent effects on the reactivity of solvated electrons with charged solutes in methanol/water and ethanol/water mixed solvents

1990 ◽  
Vol 94 (12) ◽  
pp. 4891-4896 ◽  
Author(s):  
Charles C. Lai ◽  
Gordon R. Freeman
Keyword(s):  
Solvent Effects ◽  
Mixed Solvents ◽  
Solvated Electrons

Solvent effects on the reactivity of solvated electrons with organic solutes in 1-butylamine–water mixtures

1996 ◽  
Vol 74 (3) ◽  
pp. 300-306 ◽  
Author(s):  
Yixing Zhao ◽  
Gordon R. Freeman
Keyword(s):  
Solvent Effects ◽  
Rate Constants ◽  
Pure Water ◽  
Strong Dependence ◽  
Mixed Solvents ◽  
Reaction Rates ◽  
Organic Solutes ◽  
Rich Region ◽  
Water Solvent ◽  
Solvent Molecules

The values of the rate constants of the reactions of es− with the efficient scavengers nitrobenzene and acetone are ≥ 2 × 106 m3 mol−1 s−1 in the whole range of 1-butylamine–water mixtures at 298 K; the reaction rates in the mixed solvents vary approximately as the solvent fluidity. In pure butylamine at 298 K, k2(es− + nitrobenzene) = 84 × 106 m3 mol−1 s−1 and k2(es− + acetone) = 7.3 × 106 m3 mol−1 s−1. The values of the rate constants of the reactions of es− with the inefficient scavengers phenol and toluene are < 2 × 105 m3 mol−1 s−1 in the whole range of 1-butylamine–water mixtures at 298 K and have a maximum at 50 mol% water and a minimum at 99 mol% water. In pure 1-butylamine at 298 K, k2(es− + phenol) = 1.0 × 104 m3 mol−1 s−1 and k2(es− + toluene) = 0.28 × 104 m3 mol−1 s−1. The reaction rates with inefficient scavengers show strong dependence on the solvent composition and selective solvation of electron and scavenger. In the amine-rich region (0–30 mol% water), the rate constants increase with the increase of viscosity, indicating the chemical participation of solvent molecules in the reaction. In the water-rich region from 50 to 99 mol% water, the decrease of the rate constants indicates the nonhomogeneous solvation of the electrons by water and of the organic solutes by 1-butylamine. From 99 mol% to pure water the rate constant increases rapidly, which we attribute to insufficient 1-butylamine to coat the phenol or toluene molecules. The variation of the activation energies E2 for the efficient scavengers, 14–27 kJ mol−1, are similar to the variation of Eη in the mixed solvents. The values of E2 for the inefficient scavengers are from 15 to 38 kJ mol−1 for phenol and from 6 to 21 kJ mol−1 for toluene. Both k2 and E2 for the inefficient scavenger reactions show a correlation with the temperature coefficient −dEAmax/dT of the optical absorption of es− in the mixed solvents, but the reason is obscure. Key words: 1-butylamine–water solvent, solvated electron, organic solutes, reactivity, solvent effects.

Solvent effects on the reactivity of solvated electrons with ammonium and nitrate ions in 1-butanol–water solvents

1993 ◽  
Vol 71 (9) ◽  
pp. 1303-1310 ◽  
Author(s):  
Ruzhong Chen ◽  
Gordon R. Freeman
Keyword(s):  
Solvent Effects ◽  
Pure Water ◽  
Reaction Rates ◽  
Dielectric Relaxation Time ◽  
Unusual Behavior ◽  
Solvated Electrons ◽  
Water Solvent ◽  
Electrical Conductances ◽  
Average Size ◽  
Effective Reaction

Values of the rate constants, k2 (106 m3 mol−1 s−1), of solvated electrons,[Formula: see text] with several related salts, in pure water and pure 1-butanol solvents at 298 K are, respectively, as follows: LiNO3, 9.2, 0.19; NH4NO3, 10, 8.3; NH4ClO4, 1.5 × 10−3, 12 in 20 mol% water; LiClO4, 1.0 × 10−4, < 1.0 × 10−4. The value of [Formula: see text] in water solvent is 48 times larger than that in 1-butanol solvent, whereas [Formula: see text] in water is 10−4 times smaller than the value in 1-butanol. This enormous reversal of solvent effects on [Formula: see text] reaction rates is the first observed for ionic reactants. The solvent participates chemically in the [Formula: see text] reaction, and the overall rate constant increases with increasing viscosity and dielectric relaxation time. This unusual behavior is attributed to a greatly increased probability of reaction of an encounter pair with increasing duration of the encounter. Effective reaction radii κRr for [Formula: see text] and [Formula: see text] were estimated with the aid of measured electrical conductances of the salt solutions in all the solvents. Values of κRr are (2–7) × 10−10 m, except for NH4,s+ in 100 and 99 mol% water, which are 2.6 and 2.7 × 10−14 m, respectively. The effective radii of the ions for mutual diffusion increase with increasing butanol content of the solvent, from ~50 pm in water to ~150 pm in 1-butanol, due to the increasing average size of the molecules that solvate the ions.

Dissociation of Hydroxamic Acids: Solvent Effects

1993 ◽  
Vol 58 (5) ◽  
pp. 1109-1121 ◽  
Author(s):  
Otto Exner ◽  
Martin Hradil ◽  
Jiří Mollin
Keyword(s):  
Ionic Strength ◽  
Solvent Effects ◽  
Dissociation Constants ◽  
Mixed Solvents ◽  
Hydroxamic Acids ◽  
Polar Solvents ◽  
Benzohydroxamic Acid ◽  
Methyl Cellosolve ◽  
Methyl Derivatives

The dissociation constants of benzohydroxamic, 4-chlorobenzohydroxamic, and 4-nitrobenzohydroxamic acids, and their N-methyl and O-methyl derivatives, were measured spectrophotometrically or potentiometrically in mixtures of 2-propanol and water. The results were extrapolated to zero ionic strength. The ratio of dissociation constants of the N-methyl and O-methyl derivatives can be taken to represent - with some approximation - the ratio of NH and OH acidities of the parent acid. This ratio increases with substitution by electron-attracting substituents, and decreases with solvent permittivity: some irregularities might be attributable to the effects of mixed solvents, It follows that 4-nitrobenzohydroxamic acid behaves essentially as N-acid in all solvents, 4-chlorobenzohydroxamic acid only in 90% 2-propanol or 80% methyl cellosolve. In benzohydroxamic acid the NH and OH acidities are comparable, the latter prevails slightly in water, the former in less polar solvents. Some apparent discrepancies in the literature can be explained in the same terms, only a few results have not yet been explained.

Solvent effects on the supercritical gas extraction of coal The role of mixed solvents

1982 ◽  
Vol 5 (3-4) ◽  
pp. 241-246 ◽  
Author(s):  
John R. Kershaw
Keyword(s):  
Solvent Effects ◽  
Mixed Solvents ◽  
Gas Extraction

Solvent Effects on Reactivity of Solvated Electrons with Nitrate Ion and on Electrolyte Conductivity in C1 to C10 n-Alcohols

1995 ◽  
Vol 99 (14) ◽  
pp. 4970-4975 ◽  
Author(s):  
Ruzhong Chen ◽  
Gordon R. Freeman
Keyword(s):  
Solvent Effects ◽  
Solvated Electrons ◽  
Nitrate Ion ◽  
Electrolyte Conductivity

Weak complexes of sulphur and selenium: a thermodynamic view on solvent effects in mixed solvents

1982 ◽  
Vol 80 ◽  
pp. 229-234 ◽  
Author(s):  
S. Wasif ◽  
S.B. Salama
Keyword(s):  
Solvent Effects ◽  
Mixed Solvents ◽  
Weak Complexes

Substituent and solvent effects on the reaction between 2,6-Di-t-butyl-α-(3,5-di-t-butyl-4-oxocyclohexa-2,5-dien-1-ylidene)-p-tolyloxyl (galvinoxyl) and phenols

1978 ◽  
Vol 31 (6) ◽  
pp. 1201 ◽  
Author(s):  
N Nishimura ◽  
K Okahashi ◽  
T Yukutomi ◽  
A Fujiwara ◽  
S Kubo
Keyword(s):  
Carbon Tetrachloride ◽  
Binary Mixtures ◽  
Solvent Effects ◽  
Rate Constants ◽  
Isotope Effects ◽  
Mixed Solvents ◽  
Transition States ◽  
Activation Parameters ◽  
Substituted Phenols ◽  
Kinetic Behaviour

Rate constants and associated activation parameters for the reaction of galvinoxyl with substituted phenols were obtained in carbon tetrachloride and in cyclohexane-dioxan binary mixtures. Substantial isotope effects were observed for O-deuterated phenols. The rate constants are correlated with σ+ values. These findings are discussed by considering the polar contribution of substituents to the stabilization of the transition states. In the mixed solvents, the kinetic behaviour is well expressed by the equations which are based on the theory of Kondo and Tokura.

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