Transformed entropy

Note that although AfH ° values for species are independent of pH, this is not true for Af/T ° values of reactants consisting of two or more species because the r are functions of pH. The pseudoisomer group has a corresponding standard transformed entropy of formation given by... 

Enthalpies of Reaction from the Standard Enthalpies of Formation of Species II 10.3 Calculation of Standard Transformed Entropies of Biochemical Reactions I, 10.4 Effect of Temperature... 

CALCULATION OF STANDARD TRANSFORMED ENTROPIES OF BIOCHEMICAL REACTIONS... 

The determination of standard transformed enthalpies of biochemical reactions at specified pH, either from temperature coefficients of apparent equilibrium constants or by calorimetric measurements, makes it possible to calculate the corresponding standard transformed entropy of reaction using... 

Calculation of Standard Transformed Entropies of Biochemical Reactions... 

P number of different kinds of phases in a system Af standard transformed entropy of formation of... 

S transformed entropy of a system at specified T, P, 0 Pi standard chemical potential of species i at specified... 

The corresponding standard transformed entropies of reaction are given by... 

As the pH increases, the change in the transformed enthalpy becomes less favorable for hydrolysis, but the effect is small. On the other hand the transformed entropy increases rapidly with pH and causes the equilibrium to move further to the right. 

Since coenzymes, and perhaps other reactants, are in steady states in living cells, it is of interest to use a Legendre transform to define a further transformed Gibbs energy G" that provides the criterion for spontaneous change and equilibrium at a specified pH and specified concentrations of coenzymes. This process brings in a further transformed entropy S" and a further transformed enthalpy H", but the relations between these properties have the familiar form. 

The polymer F of formaldehyde is called polyoxymethylene or paraformaldehyde. It contains two OH groups, one at each end of the molecule, but these are omitted for clarity in the structural formula shown in Figure 7.14. This shows that one molecule of water, which is present everywhere even in the most careful work, has been incorporated. If these terminal OH groups are functionalized, paraformaldehyde can be used as plastic. When paraformaldehyde is heated with acid, it is transformed (entropy gain) into the cyclic trimer B from Figure 7.14, which is called 1,3,5-trioxane. 

Based on knowledge of heats and temperatures of transformations, entropies of liquid, gaseous and other transformed phases can be determined. Similarly, it is possible with the knowledge of heats of formation and temperatures of equilibrium to determine entropy in many cases. In case of stable compounds, the integration method (Fig. 6.5) is used for entropy determination. 

R. A. Alberty, Standard molar entropies, standard entropies of formation, and standard transformed entropies of formation in the thermodynamics of enzyme-catalyzed reactions, J. Chem. Thermodyn., in press. 

Note the similarity of equations 3.2-2, 3.3-7, and 3.3-8. Thus the definition of G by use of a Legendre transform automatically brings in a transformed entropy S and a transformed enthalpy H. ... 

The function of pH and ionic strength that yields the standard transformed entropy of formation of a reactants is obtained by the following program ... 

Module[ do, dH), ( This program derives the function of pH and ionic strength (is) that gives the standard transformed entropy of formation of a reactant (sum of species) at 298.15 K. The entropy is given in J K -1 mol -1. ) dG =calcdGmat[speciesmat] dH = calcdHmat[speciesmat] ... 

Table 3.3 Standard transformed entropies of formation in J K moP of inorganic phosphate at 298.15 K.

This program can be used to calculate standard transformed Gibbs energies of reaction, standard transformed enthalpies of reaction, standard transformed entropies of reaction and the change in the binding of hydrogen ions in a reaction. 

---