Acetate complex thermodynamics

Table 11. Thermodynamic data for the Ln(III) mono-acetate complexes...

Table 2. Thermodynamic functions for the formation of acetate complexes, in perchlorate media at 254 C. All values of AH0 determined calorimetrically except for acetic acid at 1=0 (temperature coefficient 0—60° C)...

Shock, E. L. Koretsky, C. M. (1993). Metal-organic complexes in geochemical processes calculation of standard partial molal thermodynamic properties of aqueous acetate complexes at high pressures and temperatures. Geochimica et Cosmochimica... 

The antiinflammatory drugs indomethacine (l-(p-chlorobenzoyl)-5-methoxy-2-methyl-indole acetate) and lonazolac (3-p-chlorophenyl)-l-phenyl-pyrazole-4-acetate) form thermodynamically stable copper complexes in aprotic solutions, which are highly superoxide dismutase active An example for the structure of these... 

Several criteria help to distinguish between inner- and outer-sphere complexes, although not always unambiguously. For instance, Choppin (1971) and Choppin and Bertha (1973) have used the thermodynamic A// and A5 parameters. They have assigned, in aqueous solutions, a predominantly outer-sphere character to CL, Br, L, ClOj, NOj, sulfonate and trichloroacetate complexes and an inner-sphere character to F, lOj, SO and acetate complexes. Moreover, these authors have related this ordering to the pKa values of the ligands. On the other hand, a group of Russian authors have postulated that iimer- and outer- sphere complexes may be studied separately by spectrophotometric methods, but this is subject to some doubt (vide infra). 

In the present case, each endpoint involves—in addition to the fully interacting solute—an intact side chain fragment without any interactions with its environment. This fragment is equivalent to a molecule in the gas phase (acetamide or acetate) and contributes an additional term to the overall free energy that is easily calculated from ideal gas statistical mechanics [18]. This contribution is similar but not identical at the two endpoints. However, the corresponding contributions are the same for the transfonnation in solution and in complex with the protein therefore, they cancel exactly when the upper and lower legs of the thermodynamic cycle are subtracted (Fig. 3a). 

On the other hand, the presence of CN ions greatly increases the zone of corrosion, owing to the formation of complex ions. Silver, therefore, is thermodynamically stable in reducing acids, e.g. hydrochloric acid, acetic acid, phosphoric acid, provided oxidising substances are absent. 

Unfortunately, for all these reasons the conclusions cannot be applied quantitatively for description of the pH effects in the RCH-RP process. There are gross differences between the parameters of the measurements in [97] and those of the industrial process (temperature, partial pressure of H2, absence or presence of CO), furthermore the industrial catalyst is preformed from rhodium acetate rather than chloride. Although there is no big difference in the steric bulk of TPPTS and TPPMS [98], at least not on the basis of their respective Tolman cone angles, noticable differences in the thermodynamic stability of their complexes may still arise from the slight alterations in steric and electronic parameters of these two ligands being unequally sulfonated. Nevertheless, the laws of thermodynamics should be obeyed and equilibria like (4.2) should contribute to the pH-effects in the industrial process, too. 

Osmotic press data for solns of NC in acet have been obtained by Huggins(Ref 21), vapor tension s of gels by Schult2( Ref 15) and by Calvet(Ref 22), sedimentation rates by Moisimann et al (Refs 24 25), viscosity vs NC concn by Wissler (Ref 36), thermodynamic props by Munster (Ref 41), and various other props of NC-acet solns are discussed in Refs 13,23,26,29,32,34,35,38,39 44. The absorption spectra of acet are recorded by Pauling (Ref 30) and the reaction with 1,3,5-TNB, in the presence of an alkali, to give a black solid complex has been noted by Kimura (Ref 43)... 

Early members of the carboxylate series (< four carbon atoms) form many stable coordination complexes. Formic acid offers the advantage of minimal steric requirements, while thermodynamic and kinetic data reveal that frequently propionic acid forms stable complexes at a faster rate than acetic acid. Derivatives of higher acids (> four carbon atoms) show the same chemical characteristics except that, as the carbon chain of the acid grows, the tendency to coordinate decreases. 

The thermodynamic stability of the binuclear site has been demonstrated by the spontaneous assembly of [Fe20(02CR)2L2] (13) from ferric salts in the presence of water, an alkyl carboxylate salt, and a tridentate nitrogen donor ligand L that can cap an octahedral face on iron (8). Suitable ligands include tris(pyrazolyl)borates and 1,4,7-triazacyclononanes. Structure (13) is in essence a portion of the basic ferric acetate structure. The complexes are excellent physical and structural models of the diiron sites and model some aspects of reactivity including redox activity and interconversion of the oxo and hydroxo bridge. 

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