Switchover of reactions of solvated electrons with nitrate ions and ammonium ions in propanol–water solvents

1993 ◽  
Vol 71 (9) ◽  
pp. 1297-1302 ◽  
Author(s):  
Tae Bum Kang ◽  
Gordon R. Freeman
Keyword(s):  
Rate Constants ◽  
Pure Water ◽  
Reaction Rates ◽  
Binary Solvents ◽  
Ammonium Ions ◽  
Concentrated Solutions ◽  
Solvated Electrons ◽  
Reaction Rate Constants ◽  
Water Solvent ◽  
Arrhenius Temperature

The reaction rate constants of [Formula: see text] with ammonium nitrate (~ 0.1 mol m−3) in 1-propanol-water and 2-propanol–water binary solvents correspond to [Formula: see text] reaction in the water-rich solvents, and to [Formula: see text] reaction in alcohol-rich solvents. The overall rate constant is smaller in solvents with 40–99 mol% water, with a minimum at 70 mol% water. The Arrhenius temperature coefficient is 26 kJ mol−1 in each pure propanol solvent, increases to 29 kJ mol−1 at 40 mol% water, then decreases to 17 kJ mol−1 in pure water solvent. The high reaction rates in the single component solvents, alcohol or water, are limited mainly by solvent processes related to shear viscosity (diffusion) and dielectric relaxation (dipole reorientation). Rate constants reported for concentrated solutions (50–1000 mol m−3) of ammonium and nitrate salts in methanol (Duplâtre and Jonah. J. Phys. Chem. 95, 897 (1991)) have been quantitatively reinterpreted in terms of the ion atmosphere model.

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.

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.

scholarly journals Optical absorption spectra of solvated electrons in 1-butylamine–water mixed solvents

1995 ◽  
Vol 73 (12) ◽  
pp. 2126-2130 ◽  
Author(s):  
Yixing Zhao ◽  
Gordon R. Freeman
Keyword(s):  
Optical Absorption ◽  
Absorption Spectra ◽  
Pure Water ◽  
Mixed Solvents ◽  
Binary Solvents ◽  
Optical Absorption Spectra ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Selective Solvation ◽  
Ideal Mixing

The optical absorption spectra of es− in 1-butylamine–water mixed solvents increase smoothly in energy and intensity as the water content is increased, with the exception of a small decrease in intensity on going from 95 to 100 mol% water. At 298 K the value of Gεmax increases from 1.42 × 10−21 m2/16 aJ (8.6 × 103 es−L/100 eV mol cm) in pure 1-butylamine to 8.3 × 10−21 m2/16 aJ (50 × 103 es−L/100 eV mol cm) in pure water, and the value of EAmax increases from 115 zJ (0.72 eV) to 278 zJ (1.74 eV). In the pure amine, if G(es−) = 0.27, then εmax = 5.3 × 10−21 m2/es− (3200 m2/mol). The solvent composition dependences of Gεmax and EAmax indicate little selective solvation of es− by water; this might be due to relatively "ideal" mixing of water and amine in the binary solvents. The temperature coefficient −dEAmax/dT = 0.43 zJ/K in pure 1-butylamine, 0.47 in pure water, and has a minimum of 0.27 in the 50:50 mixture. Keywords: 1-butylamine–water mixed solvents, optical absorption spectra, solvated electron, temperature dependence.

Reaction Rate Constants from Classical Trajectories of Atom-Diatomic Molecule Collisions

2008 ◽  
Vol 63 (3-4) ◽  
pp. 159-169
Author(s):  
Hamzeh M. Abdel-Halim ◽  
Sawsan M. Jaafreh
Keyword(s):  
Cross Sections ◽  
Rate Constants ◽  
Potential Energy Surfaces ◽  
Diatomic Molecules ◽  
Equations Of Motion ◽  
Strong Dependence ◽  
Three Dimensional ◽  
Reaction Rates ◽  
Classical Trajectory ◽  
Reaction Rate Constants

Classical trajectory calculations for various atom-diatomic molecules were preformed using the three-dimensional Monte Carlo method. The reaction probabilities, cross-sections and rate constants of several systems were calculated. Equations of motion, which predict the positions and momenta of the colliding particles after each step, have been integrated numerically by the Runge-Kutta-Gill and Adams-Moulton methods. Morse potential energy surfaces were used to describe the interaction between the atom and each atom in the diatomic molecules. The results were compared with experimental ones and with other theoretical values. Good agreement was obtained between calculated rate constants and those obtained experimentally. Also, reasonable agreement was observed with theoretical rate constants obtained by other investigators using different calculation methods. The effects of the temperature, the nature of the colliding particles and the thermochemistry were studied. The results showed a strong dependence of the reaction rates on these factors.

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.

scholarly journals Prediction of esterification rate constants for secondary alkan-2-ols based on one- and two-parameter Taft equations

2020 ◽  
Vol 45 ◽  
pp. 146867831989184
Author(s):  
Ján Vojtko ◽  
Jaroslav Durdiak ◽  
Zuzana Lukáčová-Chomisteková ◽  
Peter Tomčík
Keyword(s):  
Rate Constants ◽  
Equilibrium Constants ◽  
Correlation Equation ◽  
Reaction Rates ◽  
Experimental Conditions ◽  
Monocarboxylic Acids ◽  
Reaction Rate Constants ◽  
Inductive Effects ◽  
Esterification Rate ◽  
Two Parameter

Equilibrium constants and reaction rate constants for the esterification of secondary alkan-2-ols with acetic acid were measured at 60°C in 1,4-dioxane. Taft coefficients, as single parameter (without inductive effects), and two-parameter correlation (including inductive and steric effects), of the measurements were used for the prediction of esterification rate constants for secondary alkan-2-ols with monocarboxylic acids. For this prediction, previously observed results of linear correlation of rate constants for the esterification of propan-1-ol with monocarboxylic acids measured under identical experimental conditions were applied. Two parameter Taft equations for the correlation of secondary alkan-2-ols and for monocarboxylic acids were combined, resulting in an overall correlation equation usable for the prediction of reaction rates for secondary alkan-2-ols with any monocarboxylic acid. This equation was experimentally verified for the esterification of three randomly chosen alkan-2-ols with three randomly chosen monocarboxylic acids.

Solvent effects on the reactivity of solvated electrons with ions in isobutanol/water mixed solvents

1994 ◽  
Vol 72 (4) ◽  
pp. 1083-1093 ◽  
Author(s):  
Ruzhong Chen ◽  
Yuris Avotinsh ◽  
Gordon R. Freeman
Keyword(s):  
Proton Transfer ◽  
Pure Water ◽  
Mixed Solvents ◽  
Transition Metal Ions ◽  
Dielectric Relaxation Time ◽  
Solvated Electrons ◽  
Neutral Species ◽  
Water Solvent ◽  
Solvation Structure ◽  
Hydrogen Bonded

The effective reaction radii KRr, where Rr is the reactive encounter radius and K is the probability of reaction per encounter, for [Formula: see text] with [Formula: see text], are all 0.7 ± 0.1 nm in isobutanol containing 10–20 mol% water. The value remains at 0.7 ± 0.1 nm for [Formula: see text] in pure isobutanol, and for the two transition metal ions in pure water solvent. The value for [Formula: see text] reduces to 0.35 nm in pure isobutanol and pure water solvents, whereas for [Formula: see text] in pure water solvent it is only 0.14 nm and 2.6 × 10−5 nm, respectively. The low reactivity of [Formula: see text] with [Formula: see text] in water is attributed to the symmetry of the hydrogen-bonded solvation structure of [Formula: see text] in water, and the higher reactivity of [Formula: see text] is attributed to the lower symmetry of its hydrogen-bonded solvation structure. The [Formula: see text] ions have no low-lying orbital for an electron to occupy, so either reaction occurs by proton transfer to the electron site or the neutral species must decompose. We suggest that the proton transfer or the decomposition of the neutral species is facilitated by an unsymmetrical solvation structure.Reaction of [Formula: see text] in Al(ClO4)3 solutions in water is due mainly to [Formula: see text] from hydrolysis of [Formula: see text] and partly to partially hydroxylated aluminum(III) species. Reaction of [Formula: see text] with [Formula: see text] itself appears to be negligible in water. The reactivity of the solutions of Al(ClO4)3 in isobutanol-rich solvents is 3–5 times greater than that in water.In pure C1 to C4 1-alcanol solvents the value of [Formula: see text] increases linearly with the dielectric relaxation time τ1 of the solvent. In these solvents the probability of permanent capture per encounter increases approximately as the square of the encounter duration.

Effects of altitude acclimatization on rat myoglobin. Effect of viscosity and acclimatization on myoglobin reaction rates

1959 ◽  
Vol 196 (3) ◽  
pp. 517-519 ◽  
Author(s):  
G. K. Strother ◽  
Eugene Ackerman ◽  
Adam Anthony ◽  
E. Hardin Strickland
Keyword(s):  
Rate Constants ◽  
Reaction Rate ◽  
Preliminary Investigation ◽  
Reaction Rates ◽  
Association Rate ◽  
Glycerol Water ◽  
Reaction Rate Constants ◽  
Viscous Media ◽  
Nonlinear Fashion

Equipment and procedure used in the determination of myoglobin-oxygen reaction rate constants in viscous media are described briefly. The rate constants were determined for purified extracts of myoglobin from control and acclimatized rats over the viscosity range 0.87–53 centipoise. Glycerol-water mixtures were used as the viscous media. The reaction rates were found to vary with the viscosity of the suspending medium in a nonlinear fashion. No difference was observed in the reaction rates for acclimatized versus control rats using skeletal muscle extracts. A preliminary investigation of heart muscle extracts indicates a decrease in the oxygen association rate for the acclimatized rats. The significance of the kinetic data is discussed.

Adaptation of biofilm communities in a feast-famine regime: implications for degradation of organic micropollutants

2020 ◽  
Author(s):  
Chuanzhou Liang ◽  
Nadieh de Jonge ◽  
Pedro N. Carvalho ◽  
Jeppe Lund Nielsen ◽  
Kai Bester
Keyword(s):  
Microbial Communities ◽  
Relative Abundance ◽  
Rate Constants ◽  
Reaction Rate ◽  
Selective Pressure ◽  
Reaction Rates ◽  
Ammonia Oxidizing Bacteria ◽  
Organic Micropollutants ◽  
Dna Concentration ◽  
Reaction Rate Constants

&lt;p&gt;Feast-famine moving bed biofilm reactors (MBBRs) were found to be removing a number of organic micropollutants effectively from wastewater in previous studies. It was hypothesized that micropollutant-degrading organisms in the biofilm communities were possibly enriched by feast-famine selective pressure. We established a MBBR operated in feast-famine regimes (alternating influent/effluent wastewater) to test the hypothesis. The development of degradation kinetics of 36 micropollutants and the microbial communities in the biofilm were assessed simultaneously for 19 time points during the 70-day adaptation.&lt;/p&gt; &lt;p&gt;During this adaptation, 16S rRNA gene amplicon sequencing showed that the microbial communities shifted greatly from the initial biofilm composition in the first 8 days toward a more steady development afterwards. Ammonia oxidizing bacteria (Nitrosomonas) and nitrite oxidizing bacteria (Nitrospira) were strongly enriched (both &gt; 18 % relative abundance at day 43), which led to high nitrification capability. Notably, the biofilm absorbed and nitrified ammonia during the feast regime, while releasing stored nitrate during the famine regime. Twenty-four out of studied 36 micropollutants showed enhanced reaction rate constants k (especially for propranolol up to 6600 %) during the adaptation. Maximum k values were observed between day 22 and 67 during the adaptation. DNA concentration in the biofilm was used as a proxy for biomass, and normalized reaction rate constants relative to the DNA concentration as k&lt;sub&gt;DNA&lt;/sub&gt; were used for understanding the degradation reaction rates of MPs per DNA concentration unit. During the adaptation, the DNA concentration continuously increased suggesting growth and accumulation of microorganisms. However, k&lt;sub&gt;DNA&lt;/sub&gt; of 21 micropollutants showed a decreased removal after day 11, which suggests the relative abundance of the respective degraders decreased while their absolute abundance increased. It suggests that the colonization rates of the MP degraders were slower than the non-degraders under the selective pressure of the feast-famine regime. By mining correlations between the microbial community and k&lt;sub&gt;DNA&lt;/sub&gt; of micropollutants, 88 operational taxonomic units (OTUs) belonging to different taxonomic groups were found to correlate significantly with removal rates of micropollutants (Pearson correlation coefficients, r &gt; 0.5, p &lt; 0.05). Thus, these identified OTUs are potential candidates as the degraders of the respective micropollutants. In summary, the feast-famine strategy was successful for enhancing the degradation of some compounds, but the feast-famine regime in this study was not successful in selecting microorganisms in biofilm with high removal capability for many micropollutants. Nevertheless, this study contributed to a better understanding of what occurred during the adaptation process of biofilms with potential for micropollutant degradation.&lt;/p&gt;

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