The Problem of the Description of Non‐stoichiometric Complex Formation in Liquids in Terms of Thermodynamic Equilibrium Constants

1976

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A general relation is given which allows the experimental determination of as many parameters of the orientation dependent molecular distribution function as intermolecular nuclear magnetic relaxation rates can be measured involving different interaction partners in the molecular pair. Then the construction of simple model molecular pair distribution functions from model atomic pair distribution functions is described. Finally, a method is reported which offers a qualitative determination of the configurational range involved in a given thermodynamic stability constant.Es wird eine allgemeine Beziehung angegeben, welche die experimentelle Bestimmung von so vielen Parametern einer orientierungsabhangigen molekularen Paarverteilungsfunktion gestattet, wie intermolekulare kernmagnetische Relaxationsraten gemessen werden konnen, die auf verschiedene Wechselwirkungspartner in dem Molekiilpaar zuriickgehen. Sodann wird die Konstruktion einer einfachen Modell-Molekiilverteilungsfunktion aus Modell-Atomverteilungsfunktionen durchgefiihrt. SchlieBlich wird iiber eine Methode berichtet, mit der es auf qualitativer Basis moglich ist, Auskiinfte uber den Konfigurationsbereich zu erhalten, den eine gegebene thermodynamische Stabilitatskonstante beinhaltet.

Information on the Orientation Dependent Molecular Distribution Function from Nuclear Magnetic Relaxation Data

1976

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Model Orientation Dependent Pair Distribution Functions Describing the Association of Simple Carboxylic Acids and of Ethanol in Aqueous Solution

Tutsch

1976

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Nuclear magnetic relaxation rates of the CH proton of formic acid and of the methyl and methylen protons of acetic, propionic, and butyric acid and of ethanol are reported. All these substances are dissolved in water (D2O) and the organic molecules are such that the hydrogen nuclei whose relaxation is not studied are deuterons. The corresponding deuteron relaxation rates (in H2O) have also been measured and the results are converted to yield the proton intramolecular relaxation rates and the intermolecular relaxation rates. Lastly, intermolecular proton relaxation rates which are caused by the interaction with protons in other groups have been measured. All these data are given as a function of the acid mole fraction x2. From these experimental results first coordination numbers of the acids with respect to the acid and closest distances of approach between the various hydrocarbon groups have been derived. Model molecular pair distribution functions have been constructed which show that propionic acid and butyric acid molecules undergo a change in the relative pair configuration as more and more water is added such that a side by side configuration of the hydrocarbon rests is produced. In the ethanol water mixture the structural change is the reverse one and here no hydrophobic association is observable.

A New Estimate of the H⁺ Ion Concentration in Pure Water. Part 1: A Critical Analysis of Current Treatments

1980

Elektrochemie / Fliissigkeiten / Lasungen / TransporterscheinungenIt is shown that attempts to determine the H + concentration in pure water involve a search for a species which is not analytically welldefined; thus appears the problem of what is the nature of the physical statements now available from pertinent measurements? Furthermore, it is demonstrated that both the conductance and the EMF determination of K , erroneously involve an extrapolation from an aqueous solution to the pure solvent, water. K , is not a strictly measurable quantity. Configurational definitions of the H C and OH ions are given which, using an intramolecular proton distribution function, essentially converts a statement concerning the distortion of a water molecule to species concentrations. The temperature dependence of the conventional K , is also incorporated in the characterization of nonanalytical H + and OHions. Es wird zunachst gezeigt, da8 die Frage nach der H+-Konzentration im reinen Wasser eine solche nach analytisch nicht wohldefinierten Spezies ist, dafi somit das Problem auftritt, was die Aussagen der bisher bekannten MeBverfahren eigentlich beinhalten. Es wird dann dargelegt, daB die Leitfahigkeit wie die EMK-Bestimmung von K, beide den Fehler machen, da8 sie von den Eigenschaften einer Losung auf das reine Wasser schlieflen. K , ist keine streng mefibare GroBe. SchlieBlich werden konfigurative Definitionen des H + und O H --Ions gegeben, die unter Einfuhrung einer intramolekularen Protonenverteilungsfunktion im wesentlichen auf eine begriffliche Erfassung von Verzerrungen von Wassermolekulen beruhen. Auch die Temperaturabhangigkeit der bisherigen MeBwerte fur K , wird zur Charakterisierung der nicht-analytisch definierten H + -und O H --Ionen herangezogen.