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  • enzyme catalyzed reactions  (1)
  • n-propylbenzene  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 13 (1984), S. 523-547 
    ISSN: 1572-8927
    Schlagwort(e): Calorimetry ; enthalpy ; enzyme catalyzed reactions ; equilibrium constants ; fructose ; Gibbs energy ; glucose isomerase ; heat capacity ; high pressure liquid chromatography ; thermodynamics ; xylose isomerase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermodynamics of the conversion of aqueous glucose to fructose has been investigated using both heat conduction microcalorimetry and high pressure liquid chromatography (HPLC). The reaction was carried out in both aqueous TRIS/HCl buffer and in aqueous phosphate buffer in the pH range 7 to 8 using the enzyme glucose isomerase and the cofactors CoCl2 and MgSO4. The temperature range over which this reaction was investigated was 298.15 to 358.15 K (25–85°C). We have found that the enthalpy of reaction is independent of pH over the range 7 to 8. A combined analysis of both the HPLC and microcalorimetric data leads to the following results at 25°C: ΔGo=349±53 J-mol−1, ΔHo=2780±200 J-mol−1, and ΔC p o =76±30 J-mol−1-K−1. The stated uncertainties are based upon an analysis of both the random and systematic errors inherent in the measurements. The temperature dependence of the equilibrium constant K for the process is expressed as $$RinK = - \frac{{349}}{{298.15}} + 2780(\frac{1}{{298.15}} - \frac{1}{T}) + 76(\frac{{298.15}}{T} - 1 + \ln \frac{T}{{298.15}})$$ Comparisons are made with literature data.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1572-8927
    Schlagwort(e): Aqueous solubility ; octanol-water partition coefficient ; activity coefficient ; n-propylbenzene ; ethylbenzene ; n-hexane ; di-isopropyl ether ; chloroform ; nitrobenzene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract From thermodynamics and certain assumptions it is shown that, under the usual experimental conditions, the octanol-water partition coefficient (Ko/w) of a given organic liquid should be the same whether the substance is partitioned neat or as part of a mixture. Measurements of several mixtures of n-propylbenzene (log Ko/w=3.71±0.04)+ethylbenzene (log Ko/w=3.16±0.01) clearly confirm this. It is also shown that the aqueous solubility (Sw) of a neat organic liquid can be related to its aqueous solubility (S w ′ ), when it is present at volume fraction ϕ in an organic liquid mixture, by S w ′ =γϕSw, where γ is its activity coefficient in the organic mixture. The measured S w ′ values for n-propylbenzene + ethylbenzene (γ≈1), n-hexane + nitrobenzene (γ〉1) and di-isopropyl ether + chloroform (γ〈1) are found to be in good agreement with the predicted values (average differences of, respectively, 〈2%, ≈8% and ≈6%). In general, the bounds on S w ′ are expected to be 0〈S w ′ 〈Sw.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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