Thermodynamic parameters for

Eigure 3.5 presents the dependence of A.S ° on temperature for chymotryp-sinogen denaturation at pH 3. A positive A.S ° indicates that the protein solution has become more disordered as the protein unfolds. Comparison of the value of 1.62 kj/mol K with the values of A.S ° in Table 3.1 shows that the present value (for chymotrypsinogen at 54.5°C) is quite large. The physical significance of the thermodynamic parameters for the unfolding of chymotrypsinogen becomes clear in the next section. 

Kinetic investigation of the reaction of cotarnine and a few aromatic aldehydes (iV-methylcotarnine, m-nitrobenzaldehyde) with hydrogen eyanide in anhydrous tetrahydrofuran showed such differences in the kinetic and thermodynamic parameters for cotarnine compared to those for the aldehydes, and also in the effect of catalysts, so that the possibility that cotarnine was reacting in the hypothetical amino-aldehyde form could be completely eliminated. Even if the amino-aldehyde form is present in concentrations under the limit of spectroscopic detection, then it still certainly plays no pfi,rt in the chemical reactions. This is also expected by Kabachnik s conclusions for the reactions of tautomeric systems where the equilibrium is very predominantly on one side. 

In the case of monotropic behavior, the isotropiza-tion endotherm and the corresponding thermodynamic parameters for the mesophase-isotropic transition can be obtained by isolating the mesophase when cooling from the melt and holding the temperature in a region where the transformation into the crystal is very slow... 

Bhattacharjee et al. [11] have calculated the thermodynamic parameters for hydrogenation of acrylonitrile-butadiene copolymer. 

Table 1. Thermodynamic parameters for the association of cyclodextrin with alcohol in an aqueous solution at 25 °C...

Tabic 4.10 Thermodynamic Parameters for Polymerization of Selected Monomers... 

Arrhenius parameters for nitration of 4-aikylphenyltrimethyiammonium ions in nitric acid-sulphuric acid mixtures (Table 12). It was argued that the observed Baker-Nathan order of alkyl substituent effect was, in fact, the result of a steric effect superimposed upon an inductive order. However, a number of assumptions were involved in this deduction, and these render the conclusion less reliable than one would like it would be useful to have the thermodynamic parameters for nitration of the methyl substituted compound in particular, in order to compare with the data for the /-butyl compound, though experimental difficulties may preclude this. It would not be surprising if a true Baker-Nathan order were observed because it is observed for all other electrophilic substitutions in this medium1. 

The physical nature of the sulfate complexes formed by plutonium(III) and plutonium(IV) in 1 M acid 2 M ionic strength perchlorate media has been inferred from thermodynamic parameters for complexation reactions and acid dependence of stability constants. The stability constants of 1 1 and 1 2 complexes were determined by solvent extraction and ion-exchange techniques, and the thermodynamic parameters calculated from the temperature dependence of the stability constants. The data are consistent with the formation of complexes of the form PuSOi,(n-2)+ for the 1 1 complexes of both plutonium(III) and plutonium(IV). The second HSO4 ligand appears to be added without deprotonation in both systems to form complexes of the form PuSOifHSOit(n"3) +. ... 

In contrast to the situation observed in the trivalent lanthanide and actinide sulfates, the enthalpies and entropies of complexation for the 1 1 complexes are not constant across this series of tetravalent actinide sulfates. In order to compare these results, the thermodynamic parameters for the reaction between the tetravalent actinide ions and HSOIJ were corrected for the ionization of HSOi as was done above in the discussion of the trivalent complexes. The corrected results are tabulated in Table V. The enthalpies are found to vary from +9.8 to+41.7 kj/m and the entropies from +101 to +213 J/m°K. Both the enthalpy and entropy increase from ll1 "1" to Pu1 with the ThSOfj parameters being similar to those of NpS0 +. Complex stability is derived from a very favorable entropy contribution implying (not surprisingly) that these complexes are inner sphere in nature. 

TABLE III. Equations and Thermodynamic Parameters for the Extraction of Am(III) from Nitrate Media by Carbamoylmethylphosphoryl Derivatives... 

Cationic polymerization of cyclic acetals generally involves equilibrium between monomer and polymer. The equilibrium nature of the cationic polymerization of 2 was ascertained by depolymerization experiments Methylene chloride solutions of the polymer ([P]0 = 1.76 and 1.71 base-mol/1) containing a catalytic amount of boron trifluoride etherate were allowed to stand for several days at 0 °C to give 2 which was in equilibrium with its polymer. The equilibrium concentrations ([M]e = 0.47 and 0.46 mol/1) were in excellent agreement with that found in the polymerization experiments under the same conditions. The thermodynamic parameters for the polymerization of 1 were evaluated from the temperature dependence of the equilibrium monomer concentrations between -20 and 30 °C. 

The monomer 2 can be regarded as a 2,4-disubstituted-1,3-dioxolane, and the thermodynamic parameters for the polymerization may be compared with those for the polymerization of 1,3-dioxolane in methylene chloride21. ... 

Thermodynamic parameters for the lipase-catalyzed resolutions (/-PtjO nyl acetate)... 

Table 7 Comparative spectrophotometric and thermodynamic parameters for the interaction of berberine, palmatine and coralyne with poly(A) [187,207-209]...

Equation (49) applies to both the forward and reverse rate constant, /clh and Ichl- Consequently, the thermodynamic parameters for the intersystem crossing process are related according to ... 

No new absorption bands are observed in other cases, largely due to the fact that the strong absorptions of the aromatic donors obstruct the UV-spectral measurements. For the complex between CBr4 and TMPD, the quantitative analyses of the temperature and concentration-dependent absorptions of the new band at 380 nm afford the extinction coefficient of ct = 3.2 x 103 M 1 cm x, as well as the thermodynamic parameters for complex formation AH = - 4.5 kcalM x, AS = - 14 e.u., and Kda = 0.3 M x at 295 K. Such thermodynamic characteristics are similar to those of the dihalogen complexes of as well as those of other acceptors with aromatic donors. Similar results are also obtained for CBr4 associates with halide and thio-cyanide anions [5,53]. 

A and D are the exciplex or excimer components, denotes the primarily excited species, k is the limiting photoassociation equilibrium constant, AHat ASa, and are the thermodynamic parameters for the exciplex-excimer, and p is the excited state dipole moment of the complex. Note that the large dipole moment for the exciplex indicates almost complete charge transfer in the excited state, (D+, A-). rfc and r, are the fluorescence lifetimes for the complex and the component. 

The polymer-water interaction parameter (%) of cross-linked alkyl-substituted acrylamides is a function of temperature. The degree of swelling increases as % decreases. Thermodynamic parameters for interpreting the LCST phenomenon are described elsewhere [32], Figure 10 is the plot of % versus tempera-... 

Regardless of the relative importance of polar and nonpolar interactions in stabilizing the cyclohexaamylose-DFP inclusion complex, the results derived for this system cannot, with any confidence, be extrapolated to the chiral analogs. DFP is peculiar in the sense that the dissociation constant of the cyclohexaamylose-DFP complex exceeds the dissociation constants of related cyclohexaamylose-substrate inclusion complexes by an order of magnitude. This is probably a direct result of the unfavorable entropy change associated with the formation of the DFP complex. Thus, worthwhile speculation about the attractive forces that lead to enantiomeric specificity must await the measurement of thermodynamic parameters for the chiral substrates. 

For several reversible reactions, the thermodynamic parameters for reaction in the quasi-free state are given in Table 10.6 using Eq. (10.16) and the reaction scheme (I). Experimental data for AX°(X = G, H, or S) are taken from Holroyd et al., (1975, 1979) and Holroyd (1977), while Table 10.5A provides data on AX r°, except for TMS (vide supra). The chief uncertainty in these calculations is the experimental determination of V0. It is remarkable that all thermodynamic parameters of reaction in the quasi-free state are negative in the same way as for the overall reaction. In particular, the entropy change is relatively large and probably for the same reason as for the overall reaction (Holroyd, 1977). 

In order to obtain thermodynamic parameters for the isomerization process, a kinetic study was carried out. The thermal isomerization of syn-2 to anti-2 shows a first-order dependence on the concentration of syn-2 in accord with Eq. (1). 

The hydrogens within the octahedral olefin-dihydride intermediate are transferred consecutively with overall cis addition, and the rate-determining step (k9) is olefin insertion to give the alkyl- hydride. Kinetic and thermodynamic parameters for nearly all the steps of Fig. 1 have been estimated for the cyclohexene system. Because the insertion reaction is generally believed to require a cis disposition of the hydride and olefin... 

Table 5 lists equilibrium data for a new hypothetical gas-phase cyclisation series, for which the required thermodynamic quantities are available from either direct calorimetric measurements or statistical mechanical calculations. Compounds whose tabulated data were obtained by means of methods involving group contributions were not considered. Calculations were carried out by using S%g8 values based on a 1 M standard state. These were obtained by subtracting 6.35 e.u. from tabulated S g-values, which are based on a 1 Atm standard state. Equilibrium constants and thermodynamic parameters for these hypothetical reactions are not meaningful as such. More significant are the EM-values, and the corresponding contributions from the enthalpy and entropy terms. 

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