The dissociation constant for potassium methylamide ion pairs in methylamine

1978 ◽  
Vol 56 (11) ◽  
pp. 1518-1523
Author(s):  
E. Allan Symons ◽  
J. Douglas Bonnett
Keyword(s):  
Dielectric Constant ◽  
Dissociation Constant ◽  
Lower Limit ◽  
Ion Pairs ◽  
Ion Pair ◽  
Solvent Viscosity ◽  
Temperature Range ◽  
Conductance Data ◽  
Heat Of Dissociation ◽  
Good Agreement

The limiting equivalent conductance (Λ0) and ion pair dissociation constant (Kd) have been obtained for potassium methylamide in methylamine from conductance data measured over the temperature range −55 to + 25° C. The value of Kd increases from 6.3 × 10−8 mol L−1 at the highest temperature to 9.4 × 10−7 mol L−1 at the lower limit. The results show good agreement with literature data for potassium amide in ammonia after corrections for differences in solvent viscosity and dielectric constant. The heat of dissociation is −26 kJ mol−1 above −15 °C, but decreases gradually at progressively lower temperatures as a shift occurs from tight to loose ion pair structures.

The reaction of trimethylamine in liquid hydrogen sulphide: an electrical conductivity study

1983 ◽  
Vol 61 (6) ◽  
pp. 1142-1145 ◽  
Author(s):  
James D. Halliday ◽  
Patrick E. Bindner
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Constant ◽  
Hydrogen Sulphide ◽  
Liquid Hydrogen ◽  
Weak Electrolyte ◽  
Temperature Range ◽  
Conductance Data ◽  
Brønsted Base ◽  
Electrical Conductivity Study ◽  
Hydrogen Bonded

The electrical conductivity of trimethylamine solutions (2.26 × 10−4 to 2.89 × 10−1 mol L−1) in liquid hydrogen sulphide over the temperature range −72.5 °C to +25.0 °C has been measured. The data indicate that the trimethylamine behaves as a Brønsted base in liquid hydrogen sulphide [1] and is protonated to form trimethylammonium hydrogensulphide. The latter[Formula: see text]behaves as a normal weak electrolyte in a solvent of low to medium dielectric constant [Formula: see text]. The conductance data as a function of temperature also show that trimethylamine exists both as a hydrogen bonded complex with H2S and as an unassociated molecule in liquid H2S.

Anionic polymerization of styrene in oxepane (hexamethylene oxide)•counter-ion, sodium

1970 ◽  
Vol 48 (13) ◽  
pp. 2031-2034 ◽  
Author(s):  
G. Löhr ◽  
S. Bywater
Keyword(s):  
Dielectric Constant ◽  
Dipole Moment ◽  
Rate Constant ◽  
Wide Temperature Range ◽  
Anionic Polymerization ◽  
Propagation Rate ◽  
Ion Pair ◽  
Temperature Range ◽  
Counter Ion ◽  
Propagation Rate Constant

The propagation reaction in the anionic polymerization of styrene in oxepane has been studied as a function of temperature and concentration of polystyrylsodium. Conductance measurements on polystyrylsodium were also made together with determinations of density, viscosity, dielectric constant, and dipole moment of oxepane itself. The measurements enabled the propagation rate constant to be determined of the polystyryl anion at 30 °C and of the ion-pair over a wide temperature range. The results have been compared with those obtained in tetrahydrofuran and tetrahydropyran.

Electrical Conductances of Tetrabutylammonium Bromide, Sodium Tetraphenylborate and Sodium Bromide in 2-Ethoxyethanol in the Temperature Range 35–50°C

2004 ◽  
Vol 218 (5) ◽  
pp. 599-610 ◽  
Author(s):  
Purushottam Haldar ◽  
Bijan Das
Keyword(s):  
Ion Pairs ◽  
Tetrabutylammonium Bromide ◽  
Molar Conductance ◽  
Sodium Bromide ◽  
Sodium Tetraphenylborate ◽  
Temperature Range ◽  
Electrical Conductances ◽  
Conductance Data ◽  
Limiting Molar Conductance ◽  
Concentration Equation

AbstractThe electrical conductances of the solutions of tetrabutylammonium bromide (Bu4NBr), sodium tetraphenylborate (NaPh4B) and sodium bromide (NaBr) in 2-ethoxyethanol have been reported at 35, 40, 45 and 50°C. The conductance data have been analyzed by the 1978 Fuoss conductance–concentration equation in terms of the limiting molar conductance (Λ0), the association constant (KΛ) and the association diameter (R). The ionic contributions to the limiting molar conductances (Λ0) have been estimated using the “reference electrolyte” tetrabutylammonium tetraphenylborate (Bu4NPh4B). Appreciable ionic association was observed for all of these electrolytes which were found to exist in the form of solvent-separated ion-pairs in 2-ethoxyethanol. The tetrabutylammonium and tetraphenylborate ions are found to remain scarcely solvated whereas the sodium and bromide ions undergo substantial solvation in 2-ethoxyethanol medium in the temperature range investigated here.

Conductometric Study of Some Tetraalkylammonium Bromides in 2-Ethoxyethanol in the Temperature Range 35–50 °C

2004 ◽  
Vol 218 (9) ◽  
pp. 1129-1138 ◽  
Author(s):  
Purushottam Haldar ◽  
Bijan Das
Keyword(s):  
Ion Pairs ◽  
Molar Conductance ◽  
Tetraethylammonium Bromide ◽  
Temperature Range ◽  
Tetraalkylammonium Bromide ◽  
Conductance Data ◽  
Limiting Molar Conductance ◽  
Bromide Ion ◽  
Conductometric Study ◽  
Concentration Equation

AbstractThe electrical conductances of the solutions of four tetraalkylammonium bromide salts (R4NBr), namely tetraethylammonium bromide (Et4NBr), tetrapropylammonium bromide (Pr4NBr), tetrapentylammonium bromide (Pen4NBr) and tetraheptylammonium bromide (Hep4NBr) in 2-ethoxyethanol have been reported at 35, 40, 45 and 50 °C. The conductance data have been analyzed by the 1978 Fuoss conductance–concentration equation in terms of the limiting molar conductance (Λ0), the association constant (KA) and the association diameter (R). The ionic contributions to the limiting molar conductance have also been estimated. Appreciable ionic association was observed for all of these electrolytes in 2-ethoxyethanol. The tetraalkylammonium ions (R4N+) were found to remain scarcely solvated in the present solvent medium within the temperature range investigated here. The solvation of the bromide ion in these tetraalkylammonium bromide is found to be weakened as soon as the ion-pairs are formed. An increase in the temperature results in a lower level of ion-pairing for each of these salts.

Effects of substituents on ion-association properties. II. 1H N.M.R. studies of substituted pyridinium and tetraalkylammonium Bis(4-methylbenzene-1,2-dithiolato)cobaltate(III) in non-aqueous solvents

1981 ◽  
Vol 34 (11) ◽  
pp. 2321 ◽  
Author(s):  
N Tsao ◽  
Y Lim
Keyword(s):  
Dielectric Constant ◽  
Complex Anion ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Ionic Clusters ◽  
Isotropic Shift ◽  
Large Size ◽  
Pyridinium Cations

A series of nine compounds containing quaternary ammonium and substituted pyridinium cations and the bis(4-methylbenzene-1,2-dithiolato)cobaltate(III) complex anion have been prepared andtheir ion-pair properties studied by lH n.m.r. spectroscopy. Their concentration association constants in nitrobenzene at 307 K range from 9 to 20. In the pyridinium series of ion pairs, it is concludedfrom the measured isotropic shift ratios that methyl substituents at the meta and para positions favour a geometry where the anion is tilted towards the ring of the cation but the ortho substituents push the anion away from the ring. In the methyltrioctylammonium ion pair, there is linear correlation between the observed isotropic shift of the N-methyl or the N-methylene protons and the dielectric constant of the solvents (E) from 4.56 to 12.3 for the 0.06, 0.09 and 0.12 M solutions. Its implication is discussed in terms of the formation of the ionic clusters of sufficiently large size.

Structure and criticality of ionic fluids

2004 ◽  
Vol 76 (1) ◽  
pp. 19-27 ◽  
Author(s):  
W. Schröer ◽  
H. Weingärtner
Keyword(s):  
Dielectric Constant ◽  
Long Range ◽  
Ion Pairs ◽  
Electrical Conductance ◽  
Universality Class ◽  
Ion Pair ◽  
Coulomb Energy ◽  
Coulomb Interactions ◽  
Ion Distribution ◽  
Free Ions

Two properties render electrolyte theories difficult, namely the long-range nature of the Coulomb interactions and the high figures of the Coulomb energy at small ion separations. In solvents of low dielectric constant, where the Coulomb interactions are particularly strong, electrical conductance and dielectric spectra suggest that the ion distribution involves dipolar ion pairs, which then interact with the free ions and with other dipolar pairs. The dipole-dipole interactions between ion pairs lead to an increase of the dielectric constant, which in turn stabilizes the free ions, thus leading to redissociation at high salt concentrations. An equation of state that accounts for ion pairing, ion-ion pair, and ion pair-ion pair interactions rationalizes the basic features of the ion distribution. It also predicts a fluid-phase transition at low reduced temperatures, which closely corresponds to simulation results and to experimentally observed liquid-liquid phase transitions. The long-range nature of the Coulomb potential driving these transitions raises questions concerning their universality class. Experiments suggest that the Ising universality class applies, but there is cross-over to mean-field behavior rather close to the critical, not yet well explained by theory.

Flash photolysis of alkali metal anions in tetrahydrofuran and dimethoxyethane

1979 ◽  
Vol 57 (14) ◽  
pp. 1792-1800 ◽  
Author(s):  
W. A. Seddon ◽  
J. W. Fletcher ◽  
F. C. Sopchyshyn ◽  
E. B. Selkirk
Keyword(s):  
Pulse Radiolysis ◽  
Shape Function ◽  
Flash Photolysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Parent Metal ◽  
Initial Formation ◽  
Extinction Coefficients ◽  
Best Fit ◽  
Good Agreement

Flash photolysis of K−, Rb−, and Cs− in tetrahydrofuran (THF) produces the corresponding ion-pairs (K+, es−), (Rb+, es−), and (Cs+, es−), followed by the regeneration of the parent metal anion, M−. In mixed-metal solutions containing Na and M where M is K, Rb, or Cs, photolysis of Na− also forms the (M+, es−) ion-pair and M−, but with the latter then reforming Na− on an extended time scale. Similar results were obtained in dimethoxyethane (DME) at 213 K, but in this case with the initial formation of a loose ion-pair, (M+, es−)loose.Based on a Gaussian–Lorenztian shape function, the 'best-fit' optical bands for the (M+, es−) and M− species were used to simulate the experimental spectra and deduce the corresponding extinction coefficients in both solvents.The overall mechanism is complex but is in good agreement with previous interpretations deduced by pulse radiolysis.

Stereospecific 1,3-H Transfer of Indenols Proceeds via Persistent Ion-Pairs Anchored By NH···Pi Interactions

2018 ◽  
Author(s):  
David Ascough ◽  
Fernanda Duarte ◽  
Robert Paton
Keyword(s):  
Computational Analysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Chirality Transfer ◽  
Activation Barriers ◽  
Sense And Avoid ◽  
Phase Dynamics ◽  
Pi Interactions

The base-catalyzed rearrangement of arylindenols is a rare example of a suprafacial [1,3]-hydrogen atom transfer. The mechanism has been proposed to proceed via sequential [1,5]-sigmatropic shifts, which occur in a selective sense and avoid an achiral intermediate. A computational analysis using quantum chemistry casts serious doubt on these suggestions: these pathways have enormous activation barriers and in constrast to what is observed experimentally, they overwhelmingly favor a racemic product. Instead we propose that a suprafacial [1,3]-prototopic shift occurs in a two-step deprotonation/reprotonation sequence. This mechanism is favored by 15 kcal mol<sup>-1</sup> over that previously proposed. Most importantly, this is also consistent with stereospecificity since reprotonation occurs rapidly on the same p-face. We have used explicitly-solvated molecular dynamics studies to study the persistence and condensed-phase dynamics of the intermediate ion-pair formed in this reaction. Chirality transfer is the result of a particularly resilient contact ion-pair, held together by electrostatic attraction and a critical NH···p interaction which ensures that this species has an appreciable lifetime even in polar solvents such as DMSO and MeOH.

Dynamics of Ion Locking in Doubly Polymerized Ionic Liquids

2020 ◽  
Author(s):  
Swati Arora ◽  
Julisa Rozon ◽  
Jennifer Laaser
Keyword(s):  
Dielectric Constant ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Ion Pairs ◽  
Polymer Chains ◽  
Ion Motion ◽  
Charged Species ◽  
Broadband Dielectric Spectroscopy ◽  
Covalently Linked ◽  
Insight Into

<div>In this work, we investigate the dynamics of ion motion in “doubly-polymerized” ionic liquids (DPILs) in which both charged species of an ionic liquid are covalently linked to the same polymer chains. Broadband dielectric spectroscopy is used to characterize these materials over a broad frequency and temperature range, and their behavior is compared to that of conventional “singly-polymerized” ionic liquids (SPILs) in which only one of the charged species is attached to the polymer chains. Polymerization of the DPIL decreases the bulk ionic conductivity by four orders of magnitude relative to both SPILs. The timescales for local ionic rearrangement are similarly found to be approximately four orders of magnitude slower in the DPILs than in the SPILs, and the DPILs also have a lower static dielectric constant. These results suggest that copolymerization of the ionic monomers affects ion motion on both the bulk and the local scales, with ion pairs serving to form strong physical crosslinks between the polymer chains. This study provides quantitative insight into the energetics and timescales of ion motion that drive the phenomenon of “ion locking” currently under investigation for new classes of organic electronics.</div>

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