Reduction of chlorothallium(III) complexes by arsenic(III)

1973 ◽  
Vol 26 (10) ◽  
pp. 2115 ◽  
Author(s):  
PD Sharma ◽  
YK Gupta
Keyword(s):  
Ionic Strength ◽  
Acid Solution ◽  
Rate Constant ◽  
Perchloric Acid ◽  
Intermediate Formation ◽  
Chloride Ions ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Perchloric Acid Solution ◽  
Hydrogen Ion Concentration

The oxidation of arsenic(III) by thallium(III) in perchloric acid solution is inhibited by chloride ions. The reactivity of various chlorothallium(III) species is in the order Tl3+ > TlCl2+ > TlCl2+ > TlCl3 > TlCl4-. The rate decreases by increasing the hydrogen ion concentration and ionic strength. The redox process occurs by intermediate formation of a complex of thallium(III) and arsenic(III). The rate constant for the reaction between Tl3+ and arsenic(III) calculated from the data of the present investigation compared well with that of the reaction1 in the absence of chloride ions.

Mechanistic Information from the Effect of Pressure on the Kinetics of Hydrolysis of Iodopentaaquochromium(III) Ion

1975 ◽  
Vol 53 (24) ◽  
pp. 3697-3701 ◽  
Author(s):  
Milton Cornelius Weekes ◽  
Thomas Wilson Swaddle
Keyword(s):  
Ionic Strength ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Kinetics Of Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Aqueous Hclo ◽  
Conjugate Base

The rate of hydrolysis of iodopentaaquochromium(III) ion has been measured as a function of pressure (0.1 to 250 MPa) and hydrogen ion concentration (0.1 to 1.0 mol kg−1) at 298.2 K and ionic strength 1.0 mol kg−1 (aqueous HClO4–LiClO4). The volumes of activation for the acid independent and inversely acid dependent hydrolysis pathways are −5.4 ± 0.5 and −1.6 ± 0.3 cm3 mol−1 respectively, and are not detectably pressure-dependent. Consideration of these values, together with the molar volume change of −3.3 ± 0.3 cm3 mol−1 determined dilatometrically for the completed hydrolysis reaction, indicates that the mechanisms of the two pathways are associative interchange (Ia) and dissociative conjugate base (Dcb) respectively.

scholarly journals An Investigation of Some Aspects of the Coordination Chemistry of Synthetic Macroheterocyclic Ligands

2021 ◽  
Author(s):  
◽  
Peter Osvath
Keyword(s):  
Solid State ◽  
Rate Constant ◽  
Variable Temperature ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Acid Dissociation ◽  
Ligand Field ◽  
Hydrogen Ion Concentration ◽  
First Order ◽  
Chelate Rings

<p>The preparation of a range of fully saturated, unsubstituted pentaazamacrocycles is described. The macrocycles vary in ring size from fifteen to twenty members, and comprise every possible arrangement of dimethylene and trimethylene linkages between five nitroqens in a monocyclic arrangement. A new linear homologue of tetraethylene pentamine with trimethylene linkages between nitrogens is also reported. The copper(II) and nickel(II) complexes of these amines have been prepared; the conductivity and spectral properties have been determined in order to investigate their stereochemistry. The nickel(II) complexes of the two largest macrocycles appear to be five-coordinate both in the solid state and in solution. The remainder of the complexes are either five-coordinate (as the perchlorate salts in the solid state or in non-coordinating solvents) or six-coordinate (with a coordinated nitrate). Cobalt(III) complexes of the fifteen to eighteen membered macrocycles have been prepared with a variety of ligands occupying the sixth coordination site. Ligand field parameters have been derived from the electronic spectra of the complexes. The stereochemistry of the complexes and their behaviour on ligand substitution have been investigated principally by 13C n.m.r. Only a few of the numerous possible isomers of each species were formed. The structures of [Co(1, 4, 7, 10, 14-pentaazacycloheptadecane) Cl]Br0.33 Cl1.67. H2O and [Co(1, 4, 7, 11, 15-pentaazacyclooctadecane)Br]Br2, which were determined by single-crystal x-ray diffraction studies, are described. The spontaneous aquation rates of the bromo complexes have been investigated semi-quantitatively, and found to span many orders of magnitude. The most labile bromo complex [Co(1, 4, 8, 11, 15-pentaazacyclooctadecane)Br]Br2 spontaneously aquates in a matter of seconds at room temperature. The increasing strain and steric crowding caused by successive replacement of five-membered chelate rings by six-membered chelate rings, or by simply altering the sequence of five- and six-membered chelate rings is manifested in a progressive increase in the instability of the complexes. In the case of the nineteen- and twenty-membered macrocycles, this crowding and strain results in the formation of stable five-coordinate cobalt(II) complexes; for these ligands, no stable complexes were formed with the smaller cobalt(III) cation. The acid-dissociation kinetics of the copper(II) complexes have been examined in nitric acid at 298 K. A variable temperature study has also been performed on the complex of l, 4, 7, 10, 14-pentaazacycloheptadecane in order to determine the activation parameters. The complexes are labile by comparison with most tetraazamacrocyclic complexes. The dissociation reactions are first-order in complex concentration, but the acid-dependence varies. The observed rate constant is second-order in hydrogen ion concentration for the complex of 1, 4, 7, 10, 13-pentaazacyclopentadecane, first-order in hydrogen ion concentration for 1, 4, 7, 10, 14-pentaazacycloheptadecane and takes the form kobs = a[H+]2/(l+b[H+]2) for the complex of 1, 4, 7, 10, 13-pentaazacyclohexadecane. For the remainder of the complexes, the observed rate constant takes the form kobs = (c[H+] + d[H+]2)/(e + [H+]). Possible mechanisms that are consistent with the above behaviour are presented.</p>

scholarly journals An Investigation of Some Aspects of the Coordination Chemistry of Synthetic Macroheterocyclic Ligands

2021 ◽  
Author(s):  
◽  
Peter Osvath
Keyword(s):  
Solid State ◽  
Rate Constant ◽  
Variable Temperature ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Acid Dissociation ◽  
Ligand Field ◽  
Hydrogen Ion Concentration ◽  
First Order ◽  
Chelate Rings

<p>The preparation of a range of fully saturated, unsubstituted pentaazamacrocycles is described. The macrocycles vary in ring size from fifteen to twenty members, and comprise every possible arrangement of dimethylene and trimethylene linkages between five nitroqens in a monocyclic arrangement. A new linear homologue of tetraethylene pentamine with trimethylene linkages between nitrogens is also reported. The copper(II) and nickel(II) complexes of these amines have been prepared; the conductivity and spectral properties have been determined in order to investigate their stereochemistry. The nickel(II) complexes of the two largest macrocycles appear to be five-coordinate both in the solid state and in solution. The remainder of the complexes are either five-coordinate (as the perchlorate salts in the solid state or in non-coordinating solvents) or six-coordinate (with a coordinated nitrate). Cobalt(III) complexes of the fifteen to eighteen membered macrocycles have been prepared with a variety of ligands occupying the sixth coordination site. Ligand field parameters have been derived from the electronic spectra of the complexes. The stereochemistry of the complexes and their behaviour on ligand substitution have been investigated principally by 13C n.m.r. Only a few of the numerous possible isomers of each species were formed. The structures of [Co(1, 4, 7, 10, 14-pentaazacycloheptadecane) Cl]Br0.33 Cl1.67. H2O and [Co(1, 4, 7, 11, 15-pentaazacyclooctadecane)Br]Br2, which were determined by single-crystal x-ray diffraction studies, are described. The spontaneous aquation rates of the bromo complexes have been investigated semi-quantitatively, and found to span many orders of magnitude. The most labile bromo complex [Co(1, 4, 8, 11, 15-pentaazacyclooctadecane)Br]Br2 spontaneously aquates in a matter of seconds at room temperature. The increasing strain and steric crowding caused by successive replacement of five-membered chelate rings by six-membered chelate rings, or by simply altering the sequence of five- and six-membered chelate rings is manifested in a progressive increase in the instability of the complexes. In the case of the nineteen- and twenty-membered macrocycles, this crowding and strain results in the formation of stable five-coordinate cobalt(II) complexes; for these ligands, no stable complexes were formed with the smaller cobalt(III) cation. The acid-dissociation kinetics of the copper(II) complexes have been examined in nitric acid at 298 K. A variable temperature study has also been performed on the complex of l, 4, 7, 10, 14-pentaazacycloheptadecane in order to determine the activation parameters. The complexes are labile by comparison with most tetraazamacrocyclic complexes. The dissociation reactions are first-order in complex concentration, but the acid-dependence varies. The observed rate constant is second-order in hydrogen ion concentration for the complex of 1, 4, 7, 10, 13-pentaazacyclopentadecane, first-order in hydrogen ion concentration for 1, 4, 7, 10, 14-pentaazacycloheptadecane and takes the form kobs = a[H+]2/(l+b[H+]2) for the complex of 1, 4, 7, 10, 13-pentaazacyclohexadecane. For the remainder of the complexes, the observed rate constant takes the form kobs = (c[H+] + d[H+]2)/(e + [H+]). Possible mechanisms that are consistent with the above behaviour are presented.</p>

scholarly journals The adsorption of substances by fuller's earth

1931 ◽  
Vol 108 (755) ◽  
pp. 174-174
Keyword(s):  
Oxalic Acid ◽  
Acid Solution ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Rapid Rise ◽  
Hydrogen Ion Concentration ◽  
Maximum Value ◽  
Rapid Fall ◽  
Fuller’S Earth

Propionic and hexoic acids are not adsorbed by fuller's earth to any extent at any p H . Oxalic acid is adsorbed in solutions more alkaline than p H 1.5. The adsorption rises to a maximum at about p H 4 and then falls off very gradually with increasing alkalinity. At p H 12 the adsorption is about three-quarters of its maximum value. The adsorption of n -propylamine and n -butylamine is influenced by acidity in almost exactly the same way. In both cases the adsorption rises from a vanishingly small value in very acid solution to about p H 4.5. From p H 4.5 to about p H 8 the adsorption is almost independent of the hydrogen-ion concentration. In solution more alkaline than p H 9.5 there is a very rapid rise in the adsorption to a maximum at p H 11, which is immediately followed by a rapid fall to a vanishingly small value at p H 13.

THE MONO-OXALATO COMPLEXES OF IRON(III): PART II. KINETICS OF FORMATION

1965 ◽  
Vol 43 (10) ◽  
pp. 2763-2771 ◽  
Author(s):  
R. F. Bauer ◽  
W. MacF. Smith
Keyword(s):  
Rate Constant ◽  
Order Rate Constant ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Experimental Conditions ◽  
Hydrogen Ion Concentration ◽  
First Order ◽  
Independent Path ◽  
Kinetics Of ◽  
Oxalato Complexes

The kinetics of the formation of the mono-oxalato complexes of iron (III) have been examined spectrophotometrically over the range of temperatures 5 to 25 °C in an aqueous medium of ionic strength 0.50 and the range of hydrogen ion concentrations 0.03 to 0.45 M. The kinetic-ally significant paths under the conditions studied involve reactions first order in iron (III) and in bioxalate but there appears to be some decrease in the second order rate constant with increase in hydrogen ion concentration at the highest acidities and at the highest temperatures. Although there is no significant contribution to the rate by an acid-independent path first order in free oxalate under the experimental conditions, the possibility of the rate constant for such a path being greater than that first order in bioxalate is not precluded.

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