Anionic polymerization of isoprene. Ion and ion-pair contributions to polymerization in tetrahydrofuran

1967 ◽  
Vol 45 (16) ◽  
pp. 1821-1824 ◽  
Author(s):  
S. Bywater ◽  
D. J. Worsfold
Keyword(s):  
Dissociation Constant ◽  
Lithium Ion ◽  
Ion Pair ◽  
Ionic Dissociation ◽  
Free Ion ◽  
Common Ion ◽  
The Common ◽  
Kinetics Of ◽  
Tetrahydrofuran Solution ◽  
Directing Effect

The kinetics of the propagation reaction in the polymerization of isoprene initiated by butyllithium in tetrahydrofuran solution have been studied. The kinetic behavior has indicated that the reactive species involves both the polyisoprenyllithium ion-pair and the free poly-isoprenyl carbanion. The conductances of solutions of polyisoprenyllithium have been measured and the ionic dissociation constant derived. From these the free ion rate constant has been evaluated. It has also been shown that the free ion reaction may be suppressed by the common ion effect when the salt lithium tetraphenylboron is added. The rate constants for the ion-pair and free ion are 0.20 M−1 s−1 and 2.8 × 103 M−l s−1 respectively; the ionic dissociation constant is 5.0 × 10−10. Nuclear magnetic resonance determinations of the structures of the polymers formed primarily by the free carbanion, and by the ion-pair only, show that the lithium ion has only a small directing effect.

Kinetics of hypso anhydrites dissolution in water. Experimental studies

2019 ◽  
pp. 93-96
Author(s):  
A. L. Lebedev ◽  
I. V. Avilina
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Riccati Equation ◽  
Balance Equation ◽  
Experimental Studies ◽  
Common Ion ◽  
The Common ◽  
Common Ion Effect ◽  
Kinetics Of Dissolution ◽  
Kinetics Of

Experimental study of kinetics of dissolution of hypso anhydrites at 25 ᵒC made it possible to formulate model of the process in the form of a balance equation for the kinetics of dissolution of gypsum, anhydrite (first and second orders, respectively) and kinetics of precipitation of gypsum (second order). The processing of the experimental data were carried out on the basis of the solution of the Riccati equation. When taking into account the common-ion effect on the solubility of gypsum and anhydrite, the calculated values turned out to be more comparable with the experimental ones.

scholarly journals Transformation Kinetics of Burnt Lime in Freshwater and Sea Water

2020 ◽  
Author(s):  
Harald Justnes ◽  
Carlos Escudero-Oñate ◽  
Øyvind Aaberg Garmo ◽  
Martin Mengede
Keyword(s):  
Calcium Hydroxide ◽  
Magnesium Hydroxide ◽  
Open System ◽  
Sea Water ◽  
Particle Surface ◽  
Calcium Sulphate ◽  
Burnt Lime ◽  
Common Ion ◽  
The Common ◽  
Kinetics Of

The reaction kinetics of burnt lime (CaO) in contact with sea water has been elucidated and compared to its behaviour in fresh water. In the first minutes of contact between burnt lime and water, it "slaked" as CaO reacted with water to yield calcium hydroxide (Ca(OH)2). Subsequently, calcium hydroxide reacted with magnesium, sulphate and carbonate from the sea water to yield magnesium hydroxide (Mg(OH)2), calcium sulphate dihydrate (gypsum, CaSO4·2H2O) and calcium carbonate (CaCO3), respectively. In a closed system of 1% CaO in natural sea water (where the supply of sulphate, magnesium and carbonate is limited), more than 90% reacted within the first 5 hours. It is foreseen that in an open system, like a marine fjord, it will react even faster. The pH 8 of sea water close to the CaO particle surface will immediately increase to a theoretical value of about 12.5 but will, in an open system with large excess of sea water, rapidly fall back to pH 10.5 being equilibrium pH of magnesium hydroxide. This is further reduced to < 9 due to the common ion effect of dissolved magnesium in sea water and then be diluted to the sea water background pH, about 8. Field test dosing CaO particles to sea water showed that the pH of water between the particles stayed around 8.

Kinetics of Ion-Pair Effect of Aquation of Bromopentaammine Cobalt(III) Complex in Different Dicarboxylate Media

2011 ◽  
Vol 324 ◽  
pp. 166-169 ◽  
Author(s):  
Farah Zeitouni ◽  
Gehan El-Subruiti ◽  
Ghassan Younes ◽  
Mohammad Amira
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Compensation Effect ◽  
Ion Pairing ◽  
Reaction Rates ◽  
Ion Pair ◽  
Free Energy Of Activation ◽  
Different Types ◽  
Different Temperatures ◽  
Kinetics Of

The rate of aquation of bromopentaammine cobalt(III) ion in the presence of different types of dicarboxylate solutions containing tert-butanol (40% V/V) have been measured spectrophotometrically at different temperatures (30-600°C) in the light of the effects of ion-pairing on reaction rates and mechanism. The thermodynamic and extrathermodynamic parameters of activation have been calculated and discussed in terms of solvent effect on the ion-pair aquation reaction. The free energy of activation ∆Gip* is more or less linearly varied among the studied dicarboxylate ion-pairing ligands indicating the presence of compensation effect between ∆Hip* and ∆Sip*. Comparing the kip values with respect of different buffers at 40% of ter-butanol is introduced.

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