Effects of hydrogen bonding and homoconjugation on the titration curves of a synthetic polynuclear phenolic compound in non-aqueous solvents

Chatterjee, S. K.

doi:10.1139/v69-380

Cited by 20 publications

(8 citation statements)

References 3 publications

(3 reference statements)

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“…The potentiometric curves, however, showed only two to three inflections, indicating that some of the hydroxyl groups on each chain are hyperacidic, while others have roughly the same acidity. A similar study of a nonameric phenolic compound showed as well that the hydroxyl groups are neutralized in mostly a stepwise manner in the conductometric titration, whereas they are lumped together in the potentiometric titration …”

Section: Pk a Estimationmentioning

confidence: 91%

“…A similar study of a nonameric phenolic compound showed as well that the hydroxyl groups are neutralized in mostly a stepwise manner in the conductometric titration, whereas they are lumped together in the potentiometric titration. 20 Chatterjee attributes this difference to homoconjugation, which potentiometry cannot detect. Later studies considered the influence of additional functional groups on the acidity of novolac-like oligomers.…”

Section: Pk a Estimationmentioning

confidence: 99%

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Mechanism of Phenolic Polymer Dissolution: Importance of Acid−Base Equilibria

et al. 1999

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The dissolution phenomena that are the basis of microlithography are largely dependent on the acid−base equilibrium of phenolic polymers in aqueous base. Fundamental equations are derived to relate the probabilistic quantities of the critical-ionization model to experimentally measurable acid−base properties in such polymer systems: solution pH, polymer pK a, degree of polymerization, and average degree of ionization. Model predictions for the dependence of the dissolution rate on these properties support previous experimental observations. A method for estimating the pK a of phenolic polymers as a function of the average degree of ionization is developed, and the results of this approach for novolac and poly(hydroxystyrene) agree with the observed differences in the dissolution rates of these two species. These results also corroborate the hydrogen-bonding dissolution inhibition model previously reported. The change in dissolution rate accompanying the substitution of deuterium for hydrogen in the phenol group is interpreted in terms of the deuterium isotope effect on pK a.

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Section: Pk a Estimationmentioning

confidence: 91%

Section: Pk a Estimationmentioning

confidence: 99%

Mechanism of Phenolic Polymer Dissolution: Importance of Acid−Base Equilibria

et al. 1999

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“…Correlation between the charge on the phenolate oxygen and the pKa of the corresponding phenols for a group of substituted phenols, measured in water and in DMSO. 10,11 [q] dimer ) -1 / 2 (0.58 + 0.32) ) -0.45 The one-dimensional Schroedinger equation was solved using this potential and an effective mass taken to be that associated with the proton in the fictitious vibration in the transition state, 1.1610 amu. The potential energy function and the wave function solutions are presented in Figure 6.…”

Section: Frequency Of Intramolecular Proton Transfermentioning

confidence: 99%

Proton Delocalization and Hyperacidity in Some Phenolic Resins

Yan¹,

Yeh²,

Schmidling³

et al. 2001

Macromolecules

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Interaction between OH groups can produce large acidity increases in phenolic systems. We report here on the behavior of a group of oligomers of p-cresol, where the cresol units are linked to each other by -CH2-bridges. In this series the acid dissociation constant increases consistently with the length of the oligomer chain. The effect is very significant; between the monomeric cresol and the pentamer the acid dissociation constants as measured in organic solvents span 5-8 orders of magnitude. In phenols, part of the acid dissociation energy is the electrostatic work required to separate the incipient ions, and that work depends on the charge located at the oxygen of the corresponding phenolate anion. It appears that with increasing length of the oligomer chain the charge on the anion site decreases. We have found that this is caused by proton delocalization between the oxygen centers of the oligomeric anions. Proton delocalization makes possible the redistribution of charge among all the oxygen centers of the oligomer, thereby lowering the charge on any one of them and increasing the acidity of the monoanions. The reality of proton delocalization is evidenced by the 13 C NMR spectra of the monoanions. The two carbon atoms of the dimer anion are indistinguishable and produce a single line in the NMR spectrum and so do the terminal carbons of the trimer anion. These observations are in line with the results of an ab initio calculation indicating an unexpectedly low energy barrier (3.5-0.3 kcal/mol) separating the two equilibrium positions of the proton. It appears that the proton oscillates almost freely between the two positions and is effectively delocalized over both oxygen centers.

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“…The effect of hydrogen bonding on acid-base equilibria in nonaqueous solvents has been discussed (43,94,137).…”

Section: Solvent Phenomenamentioning

confidence: 99%