Kinetics of Formation and Dissociation

To begin with we eonsider formation and dissoeiation of the generalised DPs, whieh is deseribed by the reaetion Eq. (22) with the equilibrium eonstant (23). The DP formation is a seeond order reaetion due to pair eollision of two Ps. The time dependeney of the eoneentrations is given by the eorresponding ki-netie equation 

Whereas t for the DP formation depends on the initial P eoneentration cp o, r eontains the smaller rate constant and the larger segment concentration c.  

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The kinetics of formation and dissociation of the Ca2+, Sr2+ and Ba2+ complexes of the mono- and di-benzo-substituted forms of 2.2.2, namely (214) and (285), have been studied in water (Bemtgen et al., 1984). The introduction of the benzene rings causes a progressive drop in the formation rates the dissociation rate for the Ca2+ complex remains almost constant while those for the Sr2+ and Ba2+ complexes increase. All complexes undergo first-order, proton-catalyzed dissociation with 0bs — kd + /ch[H+]. The relative degree of acid catalysis increases in the order Ba2+ < Sr2+ < Ca2+ for a given ligand. The ability of the cryptate to achieve a conformation which is accessible to proton attack appears to be inversely proportional to the size of the complexed metal cation in these cases. 

The nature of the nucleation site as well as the kinetics of formation and dissociation of the H-induced and stabilized platelets have yet to be experimentally studied in detail. However, their generation in float-zone (Johnson and Herring, 1988b) as well as Czochralski-grown (Fig. 8) silicon argues against the involvement of oxygen or carbon in platelet nucleation. 

Kinetics of formation and dissociation of lanthanide complexes [La(III) = Pr, Eu, Tb, Ho, and Yb] with l-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP) in toluene-water phase were studied by monitoring the fate of La3+— arsenazo III (AZ) complex (MAZ) in the aqueous phase with the hydrophilic separator. The structures of the ligands and AZ are given below ... 

Shariah, A., and Peters, C.J. (2007) Kinetics of formation and dissociation of sH hydrogen dathrate hydrates. Proceedings of the 5th International Symposium on High Pressure Process Technology and Chemical Engineering, June 24-27, Segovia, Spain. 

A detailed tabulation of data (231, 379, 381, 382) and some isolated results (43, 76, 394, 580b, 731) for the kinetics of formation and dissociation of complexes of these ligands may be found in the literature. Representative data are presented in Table VII. Where a direct comparison is possible, stability constants measured kinetically agree with the values determined by other means. For a reaction scheme which may be represented by... 

Casey WH (2001) Clusters in solution and at interfaces Kinetics of formation and dissociation, and isotope exchange. In Banfield JF, Navrotsky A (eds) Nanoparticles in the Enviromnent and Technology. Rev Mineral Geochem (in press)... 

The kinetics of formation and dissociation of Ni(SCN)2(aq) have been studied in water and in several organic solvents, using the pressure-jump and shock wave relaxation technique at 20°C. The concentration of Ni(SCN)2(aq) ranged between 0.001 and 0.1 M. In water, only the formation of the monothiocyanato complex was observed. No background electrolyte was used, and the activity coefficients were calculated by an extended Debye-Hiickel expression. Although, this activity model is not compatible with the SIT, the ionic strengths were low. Therefore, the reported result was corrected to 25°C and the resulting value was accepted with an increased uncertainty (log, = (1.79 0.10)). 

Chattopadhyay et al [Ch 76a, Ch 76b, Ch 77] used a spectrophotometric stopped flow technique to study the kinetics of formation and dissociation of a large number of nickel complexes, with a metal to ligand ratio of 1 1, in various non-aqueous solvents. When their findings were compared with the results obtained earlier in investigations of analogous complexes of other transition metal ions [Ch 73, Ch 74], it was established that in most of the systems the above reaction follows an /d mechanism. The step determining the reaction rate was found to be the exchange between the solvent bound in the coordination sphere of the metal and the... 

Limited information on the kinetics of formation and dissociation of volatile compounds... 

Bismuth.— Tlie rate of formation of Bi in an aqueous solution of BiCls in HCl in contact with metallic bismuth is a first-order process, occurring by two stages. The first stage is faster than the second and is a diffusion-controlled reaction with an activation energy of 1.8 kcalmol". The kinetics of formation and dissociation of [Bie(OH)i8] + have been investigated. Under equilibrium conditions the pressure-jump method gives a rate law... 

The mechanism of 1 1 complex formation between palladium(II) and catechol and 4-methylcatechol has been studied in acidic media, and the rate of 1 1 (and 1 2) complex formation between silver(II) and several diols is an order of magnitude higher in basic solution than in acidic. The kinetics of formation and dissociation of the complex between cop-per(II) and cryptand (2,2,1) in aqueous DMSO have been measured and the dissociation rate constant, in particular, found to be strongly dependent upon water concentration. The kinetics of the formation of the zinc(II) and mercury(II) complexes of 2-methyl-2-(2-pyridyl)thiazolidine have been measured, as they have for the metal exchange reaction between Cu " and the nitrilotriacetate complexes of cobalt(II) and lead(II). Two pathways are observed for ligand transfer between Ni(II), Cu(II), Zn(II), Cd(II), Pb(II) and Hg(II) and their dithiocarbamate complexes in DMSO the first involves dissociation of the ligand from the complex followed by substitution at the metal ion, while the second involves direct electrophilic attack by the metal ion on the dithiocarbamate complex. As expected, the relative importance of the pathways depends on the stability of the complex and the lability and electrophilic character of the metal ion. 

M = Npi or Pt i) with lanthanide shift reagents provide models for five-co-ordinate intermediates in substitution. Kinetics of formation and dissociation of these adducts have been reported. ... 

The kinetic stability of the lanthanide complexes wifli polydentate aminocarboxylate ligands has been extensively studied mainly for gadoUunium complexes given their use as MRI contrast agents. In this case the literature clearly shows a relationship between the rigidity of the ligand and the kinetics of formation and dissociation of the metal complexes. Due to their flexible stmcture, the complexation of lanthanide ions by EDTA and DTPA is a fast process. In the case of DTPA and its derivatives, the kinetics of complexation is... 

Balogh E., R. Tripier, P. Fouskova, F. Reviriego, FI. Flandel, E. Toth, Monopropionate analogues of DOTA and DTPA kinetics of formation and dissociation of their lanthanide(iii) complexes. Dalton Trans. 2007, 3572—3581 (2007). 

Toth E., E. Briicher, I. Lazar, I. Toth, Kinetics of Formation and Dissociation of Lanthanideflll)-DOTA Complexes. Inorg. Chem. 33, 4070—4076 (1994). 

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