Complex Formation in Ether–Chloroform Systems: Comparison of Thermodynamic and Spectroscopic Results

1974 ◽  
Vol 52 (11) ◽  
pp. 2139-2142 ◽  
Author(s):  
Neil F. Pasco ◽  
David V. Fenby ◽  
Loren G. Hepler
Keyword(s):  
Complex Formation ◽  
Equilibrium Constants ◽  
Liquid Vapor

A number of procedures for evaluation of equilibrium constants and standard enthalpies of complex formation from equilibrium liquid–vapor and calorimetric results have been applied to ether–chloroform systems. The results are compared with published spectroscopic values.

Ionic dissociation in complexes of iodine with triphenylarsine and triphenylstibine

1991 ◽  
Vol 69 (4) ◽  
pp. 606-610 ◽  
Author(s):  
Ying Ru Zhang ◽  
Ira Solomon ◽  
Seymour Aronson
Keyword(s):  
Complex Formation ◽  
Chemical Nature ◽  
Equilibrium Constants ◽  
Electrochemical Technique ◽  
High Iodine ◽  
Ionic Complex ◽  
Ionization Mechanisms ◽  
Iodine Complex ◽  
Ionic Dissociation ◽  
Iodine Complexes

An electrochemical technique has been employed to study the ionization of the iodine complexes of (C6H5)3As, (C6H5)3Sb, and pyridine. Several different ionization mechanisms are proposed depending on the chemical nature and concentration of the reactants. A new ionic complex, (C6H5)3MI22+ is postulated for the interaction of iodine with (C6H5)3As and (C6H5)3Sb at high iodine concentrations. Equilibrium constants have been calculated from the emf data for the various ionization steps. Key words: triphenylarsine, triphenylstibine, iodine, complex formation, ionization.

Pressure effect on rate and equilibrium constants of reversible anionic .sigma.-complex formation between polynitroaromatics and lyate ions of water and methanol

1980 ◽  
Vol 102 (24) ◽  
pp. 7268-7272 ◽  
Author(s):  
Muneo Sasaki ◽  
Noboru Takisawa ◽  
Fujitsugu Amita ◽  
Jiro Osugi
Keyword(s):  
Complex Formation ◽  
Pressure Effect ◽  
Equilibrium Constants ◽  
Sigma Complex

1-Iodoacétylènes. IV. Relations structure–réactivité pour la complexation des 1-iodoacétylènes substitués avec des bases de Lewis

1983 ◽  
Vol 61 (1) ◽  
pp. 135-138 ◽  
Author(s):  
Christian Laurence ◽  
Michèle Queignec-Cabanetos ◽  
Bruno Wojtkowiak
Keyword(s):  
Complex Formation ◽  
Triple Bond ◽  
Vibrational Frequency ◽  
Chemical Shifts ◽  
Structural Parameters ◽  
Equilibrium Constants ◽  
Lewis Acidity ◽  
Frequency Shifts ◽  
Substituent Constants ◽  
Substituted 1

The equilibrium constants for complex formation between the substituted 1-iodoacetylènes 1–8 and the vibrational frequency shifts induced by complex formation are related to the electronic substituent constants. The 13C chemical shifts of the triple bond are also useful structural parameters for predicting the Lewis acidity of iodoalkynes.

Studies of complex formation from permittivity measurements: a statistical reexamination

1992 ◽  
Vol 70 (7) ◽  
pp. 1873-1878 ◽  
Author(s):  
Otto Exner
Keyword(s):  
Dipole Moment ◽  
Complex Formation ◽  
Classical Method ◽  
Dipole Moments ◽  
Equilibrium Constants ◽  
Statistical Treatment ◽  
Statistical Procedure ◽  
Variable Ratio ◽  
Transformation Of Variables ◽  
Permittivity Measurements

Permittivity measurements on solutions of two compounds present in a variable ratio may reveal complex formation: both the equilibrium constant and the dipole moment of the complex can be in principle estimated. However, an incorrect statistical treatment involving transformation of variables is used quite often, for example, in the classical method of Few and Smith. In this case the estimates obtained are usually biased, or loaded with such a great uncertainty that they are practically worthless. The results of numerous papers, even some recent ones, are thus completely at variance with facts. This is shown in this paper by recalculating equilibrium constants and dipole moments of the complex in 17 examples from the literature. Simultaneously, a correct and simple statistical procedure is suggested. The danger of an incorrect and (or) incomplete statistical treatment may be encountered, for the same reason, even in other, quite different, areas.

Kinetics and Equilibrium of Binding of Fe3+ by a Fulvic Acid: A Study by Stopped Flow Methods

1975 ◽  
Vol 53 (20) ◽  
pp. 2979-2984 ◽  
Author(s):  
Cooper H. Langford ◽  
Tahir R. Khan
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Fulvic Acid ◽  
Metal Ion ◽  
Equilibrium Constants ◽  
Acid Dissociation ◽  
Stopped Flow ◽  
Solution Ph ◽  
Sulfosalicylic Acid ◽  
Flow Measurements

The first report of a rate of binding of a metal ion (Fe3+) by a soluble fulvic acid is derived from stopped flow measurements. The rate of complex formation is normal in Wilkins' sense and similar to that for sulfosalicylic acid. Dissociation is slow (t1/2 > 10 s). The binding of Fe3+ by the fulvic acid in acid solution, pH = 1–2.5, was investigated by kinetic analysis in which the reaction of free Fe3+ with sulfosalicylic acid was followed by stopped flow spectrophotometry on a time scale short compared to release of Fe3+ by fulvic acid. Conditional equilibrium constants found were 1.5 ± 0.3 × 104 at pH = 1.5 and 2.5, and 2.8 ± 0.3 × 103 at pH = 1.0 at 25 °C (ionic strength 0.1).

Meisenheimer Complex Formation Between 1,3,5-Trinitrobenzene and Hydroxide Ion. Equilibrium Constants for the Dimethylformamide–Water Solvent System

1972 ◽  
Vol 50 (11) ◽  
pp. 1729-1733 ◽  
Author(s):  
E. A. Symons ◽  
E. Buncel
Keyword(s):  
Complex Formation ◽  
Aqueous Medium ◽  
Equilibrium Constant ◽  
Equilibrium Constants ◽  
Solvent System ◽  
Medium Composition ◽  
Hydroxide Ion ◽  
Spectrophotometric Methods ◽  
Water Solvent ◽  
Sigma Complex

Sigma-complex formation between 1,3,5-trinitrobenzene (TNB) and hydroxide ion has been studied quantitatively as a function of medium composition for part of the dimethylformamide (DMF)–water solvent system by spectrophotometric methods. Only a 1:1 complex is detected under the conditions of measurement, with [TNB] ≥ [OH−]. The equilibrium constant (Keq) for complex formation in 22 mol % DMF has the value 3 × 10−3 l mol−1, compared with 3 l mol−1 in purely aqueous medium. Further increases in Kcq occur as the DMF content of the medium is raised; in 50 mol % DMF Keq ≈ 105, but reliable Keq values could not be obtained in this region of medium composition. The increase in Keq with increasing DMF content is interpreted largely on the basis of hydroxide ion desolvation.

Factor analysis as a complement to band resolution. V. Complexing of pentachlorophenol and acetone in carbon tetrachloride solution

1978 ◽  
Vol 56 (23) ◽  
pp. 2959-2965 ◽  
Author(s):  
J. Korppi-Tommola ◽  
H. F. Shurvell
Keyword(s):  
Factor Analysis ◽  
Carbon Tetrachloride ◽  
Complex Formation ◽  
Infrared Spectrum ◽  
Equilibrium Constants ◽  
Complex Model ◽  
Carbon Tetrachloride Solution ◽  
Linear Relationships

Complex formation between pentachlorophenol and acetone and acetone-d6 in carbon tetrachloride solution has been studied in both the hydroxyl and carbonyl stretching regions of the infrared spectrum. Factor analysis of the digitized spectra indicates three absorbing components for each set of solutions in the hydroxyl stretching region. Concentration studies revealed roughly linear relationships between the areas of the 'free' ν(OH) band and both of the resolved complex bands, suggesting that two different 1:1 complexes occur in CCl4 solution. In the ν(CO) region only one band due to complex formation was detected. Equilibrium constants for the isotopically different complexes at about 30 °C are reported. In the hydroxyl stretching region, band resolution was also carried out using four components which gave a better fit to the observed spectrum. A set of equilibrium constants were then obtained. However, considerable difficulties were met in the calculations and in the interpretation of these results, so that the three band, two complex model is preferred.

scholarly journals Proton transfer equilibria, temperature and substituent effects on hydrogen bonded complexes between chloranilic acid and anilines

2000 ◽  
Vol 14 (3) ◽  
pp. 99-107 ◽  
Author(s):  
Gamal A. Gohar ◽  
Moustafa M. Habeeb
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Proton Transfer ◽  
Equilibrium Constants ◽  
Bond Formation ◽  
Substituent Effects ◽  
Substituted Anilines ◽  
Chloranilic Acid ◽  
Hydrogen Bond Formation ◽  
Linear Relationships

The proton transfer equilibrium constants (KPT) for 1 : 1 complex formation between Chloranilic Acid (CA) and a series ofp- andm‒substituted anilines have been measured in 1,4-dioxane spectrophotometrically. The results supported the concept of amine-solvent hydrogen bond formation (short range solvation effect). Beside, this effect, theKPTvalues were apparently affected by the electron donation power of the aniline ring substituent, which was transmitted to the interaction center via resonance and inductive effects. Linear relationships betweenKPTand σ-Hammett substituent constants, or pKvalues formandpanilines,were obtained verifying the above conclusions. The solute-solvent hydrogen bond formation might increase the reactivity of the aniline nitrogen than would the inductive effect of the alkyl group, in case of CA-N-alkyl aniline complexes. The thermodynamic parameters for the proton transfer complex formation were estimated and it was indicated that the solvent–aniline hydrogen bond formation was preferred in the case ofp-substituted aniline complexes more than in the case of the correspondingm‒isomer. It has been found that the proton transfer process was enthalpy and entropy controlled.

Chemical shifts for compounds of the group IV elements silicon and tin

1968 ◽  
Vol 46 (8) ◽  
pp. 1399-1414 ◽  
Author(s):  
B. K. Hunter ◽  
L. W. Reeves
Keyword(s):  
Chemical Shift ◽  
Complex Formation ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Shielding Effect ◽  
Spin Lattice ◽  
Group Iv Elements

Chemical shifts for 29Si in seven series of molecules of the type XnSiY4−n have been measured where Y is an alkyl group and X varies widely in electronegativity. A considerable amount of proton and fluorine chemical shift data has been obtained for the same compounds and in one series (CH3)nSiCl4−n the 13C chemical shifts in the methyl groups have been measured.The gross features of the 29Si chemical shifts are understood by considering the series (Alkyl)3SiX with the electronegativity of X widely varied. The hybridization at silicon is approximately conserved in these series and the theoretically anticipated linear dependence on electronegativity of X is demonstrated. The ligands X = O, N, and F are exceptional and these 29Si chemical shifts have a high field shift. This additional shielding has been associated with (p → d)π bonding. The approximate nature of present chemical shift theories is not likely to provide a measure of the order of (p → d)π bonding.The 29Si chemical shifts in the series XnSiY4−n are discussed and also indicate a net shielding effect with (p → d)π bonding. A comparison is always made with corresponding 13C chemical shifts. A long range proton–proton coupling in molecules Me3SnX and Me2SnX2, H—C—Si—C—H, is observed when and only when X = O, (N?), F.119Sn chemical shifts in a series of alkyltin compounds have been measured. The same dependence on the electronegativity of X in the series (Alkyl)3SnX is noted, but the variation of X is much more limited. Some shielding due to (p → d)π bonding in the series (n-Butyl)nSnCl4−n is suggested. The tin chemical shift has been measured as a function of concentration and solvent for simple methyltin bromides and chlorides. In donor solvents, it has been possible to obtain equilibrium constants for complex formation from tin dilution chemical shifts. The nature of the bonding in complexes suggested previously is consistent with the variations in the coupling constant |JSn–C–H| with concentration. The distinction between ionization and complex formation with the solvent for (CH3)2SnCl2 can be made on the basis of the concentration dependence of |JSn–C–H|The spin–lattice relaxation time T1for 13C and 29Si in natural abundance in several pure degassed compounds has been measured. These are not in the case of 13C (as has been suggested) of the order several minutes, but are always less than 50 s and in one case as low as 3–4 s. Both 29Si and 13C T1 values follow what might be expected on the basis of a dipole–dipole mechanism from the closest protons. The short value of 35 s in CS2 is probably a result of spin–rotation interaction in the liquid state.

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