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

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Applying the well-known equations of thermodynamics and statistical thermodynamics it is shown under what conditions the terming "complex formation" may be used without accompanying definition of what is understood to be a complex. Generally, when a set of thermodynamic stability constants is given this means that the liquid is divided into various environments characterized by certain amounts of standard work and mass, and the configurational ranges of the entities which appear as complexes are only implicitely defined. As an alternative to the description of the structure of the liquid in terms of the thermodynamic language the description in terms of molecular distribution functions is briefly sketched.Unter Anwendung der wohlbekannten Gleichungen der Thermodynamik und statistischen Thermodynamik wird gezeigt, unter welcher Bedingung die Bezeichnungsweise ,,Komplexbildung" benutzt werden kann, ohne daD auch eine Definition dessen gegeben werden muI3, was unter einem Komplex zu verstehen sei. Wenn im allgemeinen ein Satz von thermodynamischen Stabilitatskonstanten gegeben ist, so bedeutet dies, daD die Flussigkeit in Bereiche aufgeteilit wird, die durch einen Betrag an Standard-Arbeit und durch deren Masse charakterisiert sind. Der Konfigurationsbereich dessen, was als Komplex erscheint, ist nur implizite definiert. Als Alternative zur Beschreibung der Struktur von Flussigkeiten in thermodynamischer Sprache wird die Beschreibung mit Hilfe der molekularen Verteilungsfunktron kurz skizziert. E 3413 (Eingegangen am 24. Mai 1976)

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

Hertz

1976

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An Investigation of the Structure of Acetic Acid and the Mixture Acetic Acid/CCI₄ by the Nuclear Magnetic Relaxation Method

Berg

Hertz

Tutsch

1976

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Fliissiyk eilen I Kernniagnetische Relaxation I Losungen / Magnetische Kernresonaris lntermolecular proton magnetic relaxation rates of the methyl and hydroxyl group of acetic acid involving the magnetic interaction among the various groups are reported. The data are given as a function of the mole fraction in the mixture acetic acid/CCI,. From these experimental results model atomic pair distribution functions and model molecular pair distribution functions are derived. It is shown that in the pure acid OH and CH, never approach closely towards one another. At mole fractions x2 5 0.3 the classical dimer can be observed which, however, appears in a more or less folded form.

Model Orientation Dependent Pair Distribution Functions in Three Dimensions for the Liquid Mixtures of Propionic Acid and of Ethanol with Carbon Tetrachloride

Bender¹,

Hertz²

1977

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Proton magnetic relaxation rates of the methyl, the methylene and the OH group of propionic acid and of ethanol in the mixture with CCl4 have been measured. These compounds were partly labled by deuterons and the corresponding deuteron magnetic relaxation rates were also measured. From all these data the proton intra‐ and intermolecular relaxation rates were determined together with proton relaxation rates caused by another proton containing group. The latter results then yielded intermolecular closest distances of approach between the various groups and from these orientation dependent model pair distribution functions in three dimensions have been constructed. It has been shown that the propionic acid pair configurations in CCl4 resemble somewhat to those found in the solvent water whereas for ethanol the behaviour in the two solvents is markedly different.