Formation constants, calculation

In series 3 mixtures containing a total silver concentration of 4.0 x 10" M and a total concentration of selenite between 0.001 and 0.90 M were prepared. The pH was adjusted to about 9.5. After equilibration and phase separation the total dissolved silver concentration was measured by scintillation spectrometry. A plot of log, [Ag ] against log,o [ SeOj ] has two linear branches with slopes 0.5 and 1.5 suggesting the formation of AgSeOj (y0 ) and Ag(Se03)2" (y ). The values of the formation constants calculated from the data were log = (2.42 0.12) and log = (3.76 0.05). 

The first identified complexes of unsubstituted thiazole were described by Erlenmeyer and Schmid (461) they were obtained by dissolution in absolute alcohol of both thiazole and an anhydrous cobalt(II) salt (Table 1-62). Heating the a-CoCri 2Th complex in chloroform gives the 0 isomer, which on standirtg at room temperature reverses back to the a form. According to Hant2sch (462), these isomers correspond to a cis-trans isomerism. Several complexes of 2,2 -(183) and 4,4 -dithiazolyl (184) were also prepared and found similar to pyridyl analogs (185) (Table 1-63). Zn(II), Fe(II), Co(II), Ni(II) and Cu(II) chelates of 2.4-/>is(2-pyridyl)thiazole (186) and (2-pyridylamino)-4-(2-pyridy])thiazole (187) have been investigated. The formation constants for species MLr, and ML -" (L = 186 or 187) have been calculated from data obtained by potentiometric, spectrophotometric, and partition techniques. 

After the equivalence point, EDTA is in excess, and the concentration of Cd + is determined by the dissociation of the CdY complex. Examining the equation for the complex s conditional formation constant (equation 9.15), we see that to calculate Ccd we must first calculate [CdY ] and Cedxa- After adding 30.0 mb of EDTA, these concentrations are... 

The complexation of Pu(IV) with carbonate ions is investigated by solubility measurements of 238Pu02 in neutral to alkaline solutions containing sodium carbonate and bicarbonate. The total concentration of carbonate ions and pH are varied at the constant ionic strength (I = 1.0), in which the initial pH values are adjusted by altering the ratio of carbonate to bicarbonate ions. The oxidation state of dissolved species in equilibrium solutions are determined by absorption spectrophotometry and differential pulse polarography. The most stable oxidation state of Pu in carbonate solutions is found to be Pu(IV), which is present as hydroxocarbonate or carbonate species. The formation constants of these complexes are calculated on the basis of solubility data which are determined to be a function of two variable parameters the carbonate concentration and pH. The hydrolysis reactions of Pu(IV) in the present experimental system assessed by using the literature data are taken into account for calculation of the carbonate complexation. 

The present study is conducted under consideration of thus mentioned difficulties. The solubility measurement is applied to the present investigation, selecting the pH range 6 v 12 in which the carbonate concentration can be maintained greater than 5xl0 6 M/l. The carbonate concentration and pH of experimental solutions, both being mutually dependent in a given solution, are taken into account as two variable parameters in the present experiment and hence the final evaluation of formation constants is based on three dimensional functions. For calculation purpose, the hydrolysis constants of Pu(IV) are taken from the literature (18). In order to differentiate the influence of hydrolysis reactions on the carbonate complexation so far as possible, the calculation is based on the solubilities from solutions of carbonate concentration > 10-1 M/l and pH > 8. 

Tri- and tetraaza macrocycles A-functionalized with imidazole and pyrazole groups have been coordinated to zinc. The zinc complexes of functionalized 1,5,9-trizacyclododecane and 1,4,8, 11-tetraazacyclododecane have been synthesized, (76) and (77).680-685 The formation constants with the mono-armed 1,5,9-triazacyclododecane were calculated and found to be higher than for the non-functionalized macrocycle and coordination was demonstrated to be through four nitrogen... 

Stepwise formation constants have been determined in the system Hg2+/Cl-/diethylenetriamine (dien) and related systems by potentiometry. Thermodynamic parameters have been calculated and the contribution of the entropy term to complex stability discussed.208... 

Because E -constants for complex groups are obtainable at present only by an empirical procedure82 a corresponding analysis is not possible for aryl-, vinyl-, and other nonflexible a-type radicals. This difficulty was overcome recently by the development of a new set of steric substituent parameters. 9f for front strain phenomena. These constants are defined as the difference in heat of formation for the hydrocarbons 30 and 31. The heats of formation are calculated for this purpose by... 

Because T -> V energy transfer does not lead to complex formation and complexes are only formed by unoriented collisions, the Cl" + CH3C1 -4 Cl"—CH3C1 association rate constant calculated from the trajectories is less than that given by an ion-molecule capture model. This is shown in Table 8, where the trajectory association rate constant is compared with the predictions of various capture models.9 The microcanonical variational transition state theory (pCVTST) rate constants calculated for PES1, with the transitional modes treated as harmonic oscillators (ho) are nearly the same as the statistical adiabatic channel model (SACM),13 pCVTST,40 and trajectory capture14 rate constants based on the ion-di-pole/ion-induced dipole potential,... 

The complex formation between hydroperoxides and HALS derivatives proposed for the preceding reaction was recently postulated by two different groups of investigators. First, Carlsson determined a complex formation constant for +00H and a nitroxide on the basis of ESR measurements—. Secondly, Sedlar and his coworkers were able to isolate solid HALS-hydroperoxide complexes and characterize them by IR measurements. The accelerated thermal decomposition of hydroperoxides observed by us likewise points to complex formation. It is moreover known that amines accelerate the thermal decomposition of hydroperoxides-. Thus Denisov for example made use of this effect to calculate complex formation constants for tert.-butyl hydroperoxide and pyridineitZ.. 

Complex formation constants could also be determined directly from UV spectrophotometric measurements. Addition of tert.-butyl hydroperoxide to a solution of nitroxide I in heptane at RT causes a shift of the characteristic absorption band of NO at 460 nm to lower wavelengths (Fig. 9). This displacement allows calculation of a complex equilibrium constant of 5 1 1/Mol. Addition of amine II to the same solution causes reverse shift of theC NO" absorption band. From this one can estimate a complex formation constant for amine II and +00H of 12 5 1/Mol (23 2 1/Mol was obtained for tert.-butyl hydroperoxide and 2,2,6,6-tetramethylpipe-ridine in ref. 64b). Further confirmation for an interaction between hindered amines and hydroperoxides is supplied by NMR measurements. Figure 10a shows part of the +00H spectrum in toluene-dg (concentration 0.2 Mol/1) with the signal for the hydroperoxy proton at 6.7 ppm. Addition of as little as 0.002 Mol/1 of tetra-methylpiperidine to the same solution results in a displacement and marked broadening of the band (Fig. 10b). 

Using the UMIST Astrochemistry Database format for rate constants, calculate the rate constants at 20 and 100 K for the following reactions, giving the units for the rate constants in each case ... 

Calculate the conditional formation constant for the Zn-EDTA complex at pH 9.0 in a solution... 

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