Pyridine-2-azo-p-dimethylaniline

The reversible formation of a complex by Ni ions and the bi dentate ligand pyridine-2-azo-p-dimethylaniline is a simple and thus reliable reaction, not accompanied by side reactions [17]. Kinetic rate law and rate constants for the reaction are known. The time demand of the reaction fits the short time scales typical for micro reactors. The strong absorption and the strong changes by reaction facilitate analysis of dynamic and spatial concentration profiles. 

Ni-Pyridine Complex Formations Investigated in Micro Reactors Organic synthesis 95 [OS 95] Complex formation from Ni ions and pyridine-2-azo-p-dimethylaniline... 

OS 95] [R 5] [P 75] Plugs of pyridine-2-azo-p-dimethylaniline were inserted in a continuous Ni ion stream. Thereafter, spatial concentration profiles were monitored in the micro channels as a result of interpenetrating flow fronts due to varying mobility of the species in an electrical field [17]. 

At the Ni ion solution/ligand slug interface, the complex is formed, as evidenced by the color change [17]. Since the formation is reversible, decomposition of the complex can also be observed, on reducing the content of pyridine-2-azo-p-dimethylaniline. 

Fig. 9. Reaction volume profile for the substitution of [Fe(DMF)6]2+ by trans-pyridine-2-azo( p-dimethylaniline), pada (147).

Fig. 5. Concentration profiles of three species involved in a reaction of PADA (pyridine-2-azo-p-dimethylaniline) with nickel nitrite to form a complex within a micro-channel. Solid black lines, reactant Ni2+ concentration red points and solid lines, reactant PADA measured and calculated concentrations blue points and solid lines, product complex measured and calculated concentrations...

N.m.r. spectroscopy has been used to study enantiomeric inversions of a series of tetrahedral chelates of zinc(ii), cadmium(ii), and lead(ii). The rates of inversion depend on the nature of the metal, the donor atoms, and the structure and substituents of the chelate rings. An intramolecular diagonal-twist mechanism is suggested. Rapid complex formation kinetics between zinc(ii) and the glycine zwitterion and pada (pyridine-2-azo-p-dimethylaniline) have been studied using relaxation methods. 

From previous results (3) obtained for the reaction using Ni (aq) and the related coloured ligand pyridine-2-azo-p-dimethylaniline (PADA), it was concluded that in the presence of excess micellar SDS, both Ni (aq) and PADA were strongly adsorbed at the micelle surface where reaction occurs. The rate of reaction was markedly pH-dependent due to the protonation of the ligand, and a shift in... 

KINETIC STUDIES OF THE COMPLEX FORMATION OF NICKEL (II) IONS WITH PYRIDINE-2-AZO-p-DIMETHYLANILINE (PADA) IN NON-AQUEOUS SOLVENTS AT PRESSURES FROM 1 BAR TO 2 KBAR. 

In this work a 3ys pulse from a Rhodamine 6-G dye-laser was used to photochemically dissociate metal ion complexes, kinetic results being obtained from the subsequent recombination reactions. The ligand used to test the applicability of the approach was pyridine-2-azo-p-dimethylaniline (PADA) since the kinetics of its complexation have been studied in aqueous solution with Ni (aq) (4). The influence of micelles formed by the anionic surfactant sodium dodecyl sulphate (SDS) on this reaction was also investigated. The arrangement of the apparatus used is shown in figure (1),... 

The relaxation trace of the complexation reaction of Ni with pyridine-2-azo-p-dimethylaniline (PADA), shown in Fig. 2, was achieved by applying the SF mode. The measured time constant is in good agreement with the literature (3). 

Two preliminary accounts have appeared which report new approaches to the problem of the mechanism of complex formation in water. The reaction between Nd " and S04 was investigated by ultrasonics in H2O and D2O and it was concluded from the fact that the reaction was 2.3 times slower in D2O than in HgO (whereas the dissociation step was accelerated) that solvent exchange at the metal ion cannot be the controlling step in lanthanoid complexation reactions. A high-pressure cell with spectrophotometric detection was used in conjimction with a laser temperature-jump apparatus to measure the volumes of activation of the reaction of Co + and Ni + with the bidentate ligand pyridine-2-azo-p-dimethylaniline (1), and of Ni + with NH3. In all cases the value of AV was ca. 8 cm mol, a value which corresponds to a considerable fraction of the molar volume of water ... 

It is probable that one factor contributing to the frequent interchange-ability between zinc and cobalt(n) in enzymatic reactions is this ability of the two ions to change their co-ordination number comparatively easily. A preliminary report has appeared of a similarity in the effects of given bound ligands L on the reactions of both Zn + and Co + with pyridine-2-azo-p-dimethylaniline (1)... 

The presence of bound ligands on zinc has comparatively little effect on the rate of complex formation with pyridine-2-azo-p-dimethylaniline (1). 

The neutral bidentate ligand pyridine-2-azo-p-dimethylaniline (PADA) interacting with Ni ions... 

Extrema in the enthalpy and entropy of activation for the substitution of 2,2 -bipyridyl into Ni q in a series of water/acetonitrile mixtures correlate welf with the extrema in the physical properties of the mixture which are related to sharp changes in the solvent structure. Further reports have appeared on rate enhancements for the reaction of Ni " with pyridine-2-azo-p-dimethylaniline (pada) in micellar systems,and the kinetics of complex formation with lasalocid (X-537A) in methanol " and with poly(4-vinylpyridine) in aqueous methanol " have been reported. 

The kinetics of the reactions of cobalt(ii), nickel(ii), copper(ii), and zinc(ii) with pyridine-2-azo-p-dimethylaniline [pada (7)] in glycerol solution provide a... 

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