Chaleurs D'Interaction de Complexes par Liaison Hydrogène. 1. — Complexes Alcool ou Phénol — Pyridine

Calorimetry / Mobile OrderPartial enthalpies of mixing of pyridines in methanol, ethanol, I-butanol, water and cyclohexane were determined calorimetrically at 25°C. From these data their molar enthalpies of transfer, at infinite dilution, from the inert solvent to the H bonded solvents were calculated. They were compared with the enthalpies of H bond formation between the pyridines and the alcohols in CC14 and the enthalpies of the selfassociation bonds in the pure liquids. Although in the pure alcohols more than 95% of the molecules are at a given time involved in H bonds with an energy of about 25 kJmol-' which is markedly larger than the energy of the pyridine-alcohol bonds in CCI,, the molar enthalpy of transfer of the pyridines from an inert solvent to an H bonded one remains exothermic. A quptitative treatment of the competition between the two types of H-bonds is presented. It is based on the thermodynamics of mobile order that was recently developed. It leads to an equation that reasonably predicts the transfer enthalpies. According to this treatment the competition reduces the complexation constant by a factor KjB/(KiBKiA), K i B and K i A being the stability constants of the H bonds in the absence of competition. In water the exothermic effect is enhanced because the second 0 -H group of the molecule forms much weaker selfassociation H-bonds than the first one.Solutions / Thermodynamics

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Competition between Solute‐Solvent and Solvent‐Solvent Hydrogen Bonds: Pyridines in Alcohols and in Water

Siegel

Huyskens

Vanderheyden

1990

Ber Bunsenges Phys Chem

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Chaleurs D'Interaction de Complexes par Liaison Hydrogène. II. — Complexes Phénol — Pyridine Substituée

Neerinck

Lamberts

1966

Bulletin des Soc Chimique

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Enthalpies of hydrogen bond formation between phenol and substituted pyridines are measured by calorimetry. The obtained energies are compared with the base ionization constants in water and the Q values of the pyridine substituents. The relation formation energy to infrared frequency shift is the same as for alcohols or phenols-pyridine complexes. Distances between 0 and N atoms linked by the hydrogen bond are related to the infrared frequency shift: it is then concluded that a linear relation exists, for the complexes studied, between the heat of formation and the bond distance. Influence of steric hindrance on the bond distance is discussed.La premikre partie de ce travail (I) a trait a I'ttude des chaleurs de complexation de la pyridine avec difftrents donneurs de proton. Les enthalpies de formation sont dttermintes connaissant lachaleur de mtlange de deux solutions dilukes de chacune des deux moltcules. Une mtthode analogue avait t t t appliquke a la complexation d'amines et d'alcools aliphatiques (').Une nouvelle strie de mesures, prtsentte dans cet article, poursuit l'ttude des chaleurs de complexation du phtnol avec des pyridines diversement substitutes. La constante d'tquilibre de complexation a tt6 d6terminte prtctdemment par spectroscopie infrarouge.Cette strie de complexes oh le donneur de proton reste constant montre dans quelle mesure les proprittts des complexes similaires a accepteur constant se trouvent vtrifites. L'effet sttrique des dtrivts ortho (*) Titulaire d'une bourse de spkialisation de 1'1 W O N L .

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Étude par Spectrométrie Infrarouge de la Complexation de Phénols Substitués par la Triéthylamine

Lutgen

Damme

Zeegers‐Huyskens

1966

Bulletin des Soc Chimique

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By infrared spectrometric measurements, we have determined the complexation constants (Kia) of several complexes formed by substituted phenols with triethylamine in carbontetrachloride solution, at 27°C. Plot of log Kia in function of the o substitution constant of Hammett show two straigth lines with different slopes. The first line, containing the substituents of group I (3-4 di-CHs, p.CH3, p.1, p.Br, p.F), obeys the relation log K12 = 1,65 + 1,280.the solutions, the diminution of solubility of the complexes and the apparition, in the infrared spectra, of a large band lying between 2900 and 2200 cm-l. This result agrees also with our earlier infrared spectrometric determinations.

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Chaleurs D'Interaction de Complexes par Liaison Hydrogène. 1. — Complexes Alcool ou Phénol — Pyridine

Cited by 20 publications

References 33 publications

Competition between Solute‐Solvent and Solvent‐Solvent Hydrogen Bonds: Pyridines in Alcohols and in Water

Competition between Solute‐Solvent and Solvent‐Solvent Hydrogen Bonds: Pyridines in Alcohols and in Water

Chaleurs D'Interaction de Complexes par Liaison Hydrogène. II. — Complexes Phénol — Pyridine Substituée

Étude par Spectrométrie Infrarouge de la Complexation de Phénols Substitués par la Triéthylamine

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