The correlation of the stability constants of 1,3-dicarbonylic monochelates of Iron(III) with the acid dissociation constants of the ligand

1990 ◽  
Vol 19 (12) ◽  
pp. 1191-1197 ◽  
Author(s):  
Jos� M. Hernando ◽  
Olimpio Montero ◽  
Carlos Blanco
Keyword(s):  
Stability Constants ◽  
Dissociation Constants ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
The Stability

Thio derivatives of β-diketones and their metal chelates. V. Acid dissociation constants of some Monothio-β-diektones and stability constants of anickel(II) and a copper(II) chelate

1966 ◽  
Vol 19 (11) ◽  
pp. 2035 ◽  
Author(s):  
SHH Chaston ◽  
SE Livingstone
Keyword(s):  
Stability Constants ◽  
Mole Fraction ◽  
Dissociation Constants ◽  
Metal Chelates ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
Water Solutions ◽  
Acetyl Acetone ◽  
The Stability ◽  
Derivatives Of

The acid dissociation constants (PKD) of the monothio derivatives of acetyl-acetone, dibenzoylmethane, and 3,3,3-trifluoro-1-(2- thenoyl)acetone, viz. 4-mercap-topent-3-en-2-one (I), 3-mercapto-1,3- diphenylprop-2-en-1-one (II), and 1,1,1-trifluoro-4-mercapto-4-(2- thienyl)but-3-en-2-one (III), were determined in dioxan/water solutions with varying mole fraction (n2) of dioxan. Over a range of n2 from 0.18 to 0.44 the values of pKD were found to vary linearly with n2 as given by the equations: (I) pKD = 5.7+12.0n2; (II) pKD = 7.0+10.9n2; (III) pKD = 3.55 + 9.2n2. The thio derivatives (I), (II), and (III) have pKD values 2.0-2.7 log units lower than their oxygen analogues. The logarithm of the stability constants (log β2) for the nickel(II) and copper(II) complexes of (II) were found to be 21.7 and 22.2, respectively. For both complexes K2 > K1. Comparison with the stability constants of the dibenzoylmethane complexes shows that for nickel(II) the complex of the monothio-β-diketone is more stable than that of the β-diketone while the converse is true for copper(II).

Decomposition of some cyclic dithiocarbamates

1970 ◽  
Vol 48 (14) ◽  
pp. 2204-2209 ◽  
Author(s):  
Ronald R. Vandebeek ◽  
Serge J. Joris ◽  
Keijo I. Aspila ◽  
Chuni L. Chakrabarti
Keyword(s):  
Dielectric Constant ◽  
Dissociation Constants ◽  
Acid Dissociation ◽  
Acid Molecule ◽  
Decomposition Rates ◽  
Acid Dissociation Constants ◽  
Ring Strain ◽  
Relative Stabilities ◽  
Ph Values ◽  
The Stability

The stability of some cyclic N,N-disubstituted dithiocarbamates has been studied by the analysis of the decomposition rates at different pH values. It is concluded that the most important factors which determine the relative stabilities of three cyclic dithiocarbamates (DTC) are the solvation of the DTC acid molecule and the ring strain associated with the substituents. This has been proven by a study of (a) the decomposition rates as a function of the dielectric constant of the medium, (b) order of the stability, and (c) activation energy.The molar absorptivities and the apparent acid dissociation constants have been determined for pyrrolidine-, piperidine-, and hexamethylene-dithiocarbamates.

Dihydroxyanthraquinone complexes of zirconium

1969 ◽  
Vol 22 (11) ◽  
pp. 2321 ◽  
Author(s):  
TM Florence ◽  
YJ Farrar ◽  
HE Zittel
Keyword(s):  
Dissociation Constants ◽  
Equilibrium Constants ◽  
Alizarin Red S ◽  
Acid Dissociation ◽  
Hydroxyl Groups ◽  
Acid Dissociation Constants ◽  
Alizarin Red ◽  
Zirconium Complexes ◽  
Voltammetric Techniques ◽  
The Stability

The nature of the zirconium complexes of alizarin red S (1,2-dihydroxy- anthraquinone-3-sulphonate), alizarin (1,2-dihydroxyanthraquinone), and hystazarin (2,3-dihydroxyanthraquinone) were studied using spectrophotometric, kinetic, and voltammetric techniques. In HClO4- NaClO4, 75% methanol media, these compounds form 1 : 1 complexes with zirconium. The equilibrium constants, KC, for the reaction of zirconium with alizarin red S, alizarin, and hystazarin were found to be 2.8 x 105, 3.0 x 103, and 6.9 x 102, respectively, at 25� and μ = 1.0M. The concentration acid dissociation constants, pKca, for the dihydroxyanthraquinones in 75% methanol were determined as: alizarin red S 6.71 and 11.35; alizarin 7.31 and 11.84; hystazarin 7.57 and 11.40; at 25� and μ 1.0M. Zirconium reacts slowly with alizarin red S and alizarin, and mainly via the hydrolysed Zr(OH)22+ species, whereas the reaction with hystazarin is rapid. Rate constants were determined for the first two reactions. The zirconium-alizarin red S complex includes two coordinated hydroxyl groups, the alizarin complex one, and the hystazarin complex contains none. It is suggested that these coordinated hydroxyl groups hydrogen-bond to the sulphonate and/or quinone groups and enhance both the stability and colour of the zirconium complexes.

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