Application des relations de Taft à la complexation

Clotman, D.; Zeegers‐Huyskens, Th.

doi:10.1016/0584-8539(67)80045-x

Cited by 17 publications

(6 citation statements)

References 14 publications

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“…Using literature values for the solvent parameters (α S = 1.2, β S = 0.6) 30 and the H-bond acceptors (β = 9.0 for Quin, 31,32 β = 7.5 for HeptNH 2 , 33,34 β = 6.8 for Oct 3 N 33,34 ), it is possible to use the experimental values of the association constants in Table 1 to determine the H-bond donor parameter α for each of compounds 1−4 (eq 2).…”

Section: H-nmr Dilution Experiments Inmentioning

confidence: 99%

Quantitative Measurement of Cooperativity in H-Bonded Networks

2022

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Cooperative H-bonding interactions are a feature of supramolecular networks involving alcohols. A family of phenol oligomers, in which the hydroxyl groups form intramolecular Hbonds, was used to investigate this phenomenon. Chains of intramolecular H-bonds were characterized using nuclear magnetic resonance (NMR) spectroscopy in solution and X-ray crystallography in the solid state. The phenol oligomers were used to make quantitative measurements of the effects of the intramolecular interactions on the strengths of intermolecular H-bonding interactions between the H-bond donor on the end of the chain and a series of H-bond acceptors. Intramolecular H-bonding interactions in the chain increase the strength of a single intermolecular H-bond between the terminal phenol and quinuclidine by up to 14 kJ mol −1 in the n-octane solution. Although the magnitude of the effect increases with the length of the H-bonded chain, the first intramolecular H-bond has a much larger effect than subsequent interactions. H-bond cooperativity is dominated by pairwise interactions between nearest neighbors, and longer range effects are negligible. The results were used to develop a simple model for cooperativity in H-bond networks using an empirical parameter κ to quantify the sensitivity of the H-bond properties of a functional group to polarization. The value of κ measured in these systems was 0.33, which means that formation of the first H-bond increases the polarity of the next H-bond donor in the chain by 33%. The cumulative cooperative effect in longer H-bonded chains reaches an asymptotic value, which corresponds to a maximum increase in the polarity of the terminal H-bond donor of 50%.

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Section: H-nmr Dilution Experiments Inmentioning

confidence: 99%

Quantitative Measurement of Cooperativity in H-Bonded Networks

2022

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“…This is also the case for the complexation constant of the phenols without ortho substituents, determined in CC14 by Zeegers-Huyskens. 4 Furthermore, it appears from the work of Ratajczak and Sobczyk5 and Jadzyn and Malecki,6 that the polarity of the ab complexes, described by the dipole increment µ brought about by the complexation, increases in the complexes with triethylamine when the phenol becomes more acidic. The contraction -AVab will thus increase when the polarity of the hydrogen bond between the phenol and the amine is higher.…”

Section: Resultsmentioning

confidence: 99%

Influence of the formation of ions on the viscosity of phenol-amine mixtures

Felix¹,

Huyskens²

1975

J. Phys. Chem.

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Publication costs assisted by KUL and FCFO, Belgium Mixing of aliphatic amines with phenols brings about a spectacular increase of the viscosity which in some cases becomes more than a hundred times greater than that of the pure liquid compounds. These mixtures are also characterized by a great volume contraction, the maximum of which occurs in the vicinity of a mole fraction xa = 0.67 in phenol. The maximal viscosity does not correspond with the maximum in the volume contraction but is shifted toward higher values of xa. The electric conductivity as a function of xa shows in some cases two maxima but this is no longer the case for the product , the single maximum of which lies in the vicinity of that of the viscosity, is proportional to (w,)2Ci where (w¡) is the mean Walden product of the ions and SC¡ their total concentration. It appears that the enhancement of the viscosity occurs in the range of mole fractions where , and thus the ion concentration, becomes nonnegligible. The high value of the viscosity of this mixture is thus related to the presence of ions which are also responsible for the conductivity. These ions are not directly derived from the ab complexes although these are characterized by important volume contractions which extend to parts of the molecules outside the hydrogen bond and which depend on the acid strength of the phenol. The addition of a second phenol molecule to the ab complex causes a marked increase in the volume contraction but the 82b complexes are not yet principally responsible for ion formation and for the increase of the viscosity. This is realized by a"b complexes of still higher stoichiometry. The comparison of the and curves shows that cations of several types participate to a significant extent in the conductivity in the region of high viscosity, namely, the homoconjugated ions RgNH+NRg and the cations where R3NH"1" form a hydrogen bond with a lone pair of electrons of the oxygen atom of the phenol. An important role seems to be devoted to the anions where the phenolate ion is bonded with three phenol molecules. The viscosity depends not only on the concentration of the ions which are responsible for the conductivity but also to an important extent on the size of these ions.

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“…The relation between steric interactions and association constants have been investigated by different authors [3], [6].…”

Section: Resultsmentioning

confidence: 99%

Infrared Study of the Association Between Phenol and 1‐Azabicyclo(4,4,0)Decane (Quinolizidine) Derivatives

Binst

Nouls

1971

Bulletin des Soc Chimique

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The following values of the thermodynamic functions for the association by H bonding of phenol with I-azabicyclo(4,4,0)decane (quinolizidine) derivatives in tetrachlorethylene solution, have been determined from infrared measurements: I-azabicyclo(4,4,0)decane (I): -AH": 9.8 1 0 . 5 kcal/mole, -AGO: 2.5 1 0 . 5 kcal/ mole, -AS": 24.612 e. In connection with the spectroscopic determination of the stereochemistry of l-azabicyclo(4,4,0)decane (quinolizidine) [2] derivatives, the 1,3 non bonded interactions with the nitrogen lone pair have been correlated by infrared spectroscopy measurements with the association constant of the lone pair and the proton donor Phenol was chosen as proton donor. Although phenol is self-associated, and dimerization at low concentrations occurs, the error due to this association is small. The donor properties of phenol are almost optimal as the bonding is strong enough to be measured accurately.Finally, T. Gramstad [3] has shown that steric effects are enhanced when phenol is used as donor instead of methanol. For these reasons we expected an optimal differenciation of the measured effects.( fig. 1). DETERMINATION OF THE ASSOCIATION CONSTANTSThe association constants were measured using the free vOt, band at 3610 cm-' in a dilute solution of phenol (6 m Mole/l max. to prevent self-association) in the presence of a large excess of acceptor.

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Application des relations de Taft à la complexation

Cited by 17 publications

References 14 publications

Quantitative Measurement of Cooperativity in H-Bonded Networks

Quantitative Measurement of Cooperativity in H-Bonded Networks

Influence of the formation of ions on the viscosity of phenol-amine mixtures

Infrared Study of the Association Between Phenol and 1‐Azabicyclo(4,4,0)Decane (Quinolizidine) Derivatives

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