Symposium on the Thermodynamics of Electrolytic Dissociation: The Effect of Dielectric Constant on Acid-Base Equilibria.

Kilpatrick, Martin

doi:10.1021/cr60096a001

Cited by 17 publications

(9 citation statements)

References 19 publications

(32 reference statements)

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“…However, if ethanolation occurs the meta propenyl group should exhibit a similar behavior although in this case steric factors may hinder solvation. Evidence that solvation of para substituents may incrase or decrease the acidity of substituted benzoic acids in solvents such as benzene, alcohols, ethylene glycol and dioxane-water have been described by Davis and Hetzer [ 7 ].…”

Section: Ionization Constantsmentioning

confidence: 95%

Ionization constants of substituted benzoic acids in ethanol-water:

Bräuer¹,

Argentar²

1966

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The thermodynamic ionization constants of meta and para substituted allyland propenylbenzoic acids were determined potentiometrically in aqueous ethanol of varying ethanol concentration. The pK values increase with increasing ethanol content. The relative acid strength does not vary with change in solvent concentration except for p-propenylbenzoic acid. The ApK/A^EtOH increases wTth ethanol content of the medium until a maximum is reached around 40 wt -% ethanol. A plot of pK + log [H 2 0] versus the reciprocal of the dielectric constant of the solvent gives a nearly linear relationship to a^out 44 wt-$ ethanol. From pK values found in the literature a similar linear relationship exists for other benzoic acids. With the exception of the p-propenylbenzoic acid the cr substituent constants of the Hammett equation do not change greatly with ethanol concentration Although cr is solvent dependent for substituents such as NH 2 , OH and N0 2 groups where the electron distribution is altered because of solvation of the substituent, for none of these substituents is the dependence of sigma on solvent medium as large as that found for the p-propenyl group. This behavior may be indicative that the solvation shell surrounding the p-propenylbenzoic acid differs from that of the other benzoic acids.1.

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Section: Ionization Constantsmentioning

confidence: 95%

Ionization constants of substituted benzoic acids in ethanol-water:

Bräuer¹,

Argentar²

1966

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“…·-8. a n = n umbe r of r un s. [8] has pointed out that es timation of acid strength in mixed solvents such as water-ethanol is difficult sin ce two bases are compe tin g for the proton and two solvated protons may be formed_ In addition, the solvent dipoles will be orien ted differently around the ions and solute molecules. Thus, it is conceivable that a local unmixing of the solve nt may occur.…”

Section: Ionization Constantsmentioning

confidence: 99%

Ionization constants of substituted benzoic acids in ethanol-water

Bräuer

Durany

Argentar

1967

J. RES. NATL. BUR. STAN. SECT. A.

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Tht' thermodynamic ioniza li on conSlanls of mela and para subs lituled allyl· and p ropenyl benzoic ac ids wer£' detNmined poten tiom elr ically in aq ueous e thanol of varying elhanol co ncentra tion. The /)/\ va l ups increasl' wit h increasing e thanol content. The rela li ve acid s trength does not vary wi th 1\,.\ \Vor,\': 1 \11 , 1-alld prol,en yll)(' ll wi(' acid s. ('hangc of pK wil h dieleclric co nSl a nl , Hamm e ll Sit!IlHI constall t s. ion i zatio n ('(l il s t a llt s . pK va lu es in e thanol -wa te r, s igma ('o ns t an ts ill l't ba nol-,,,,I(' r . ,ubS lillll ('d "('nwi(' acids.

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“…The resulting equilibrium constants are a measure of the relative acid strength of the acid Ax in the solvent S. In each solvent the standard acid is the solvated proton and the results hi one medium are not comparable to those in another (19).…”

Section: Hydrocyanic Acidmentioning

confidence: 99%

“…The exhibition of the acid property is the transfer of the proton from the acid to the base and not the dissociation of the acid-base complex into separate ions. When the acid Ax reacts with the base Bx the primary reaction is Ai + Bo BiA2 (19) and in an inert (aprotic) solvent of low dielectric constant Bx" A2+ will not appreciably dissociate but may even associate to form dimers or higher polymers. The proton transfer may not be complete, and the complex may not be wholly ionic.…”

Section: Hydrocyanic Acidmentioning

confidence: 99%

“…The idea of ion acceptors can also be applied to reactions where a proton acceptor is not necessarily involved (7); for example, titanium tetrachloride which shows no measurable conductance in dry benzene or carbon tetrachloride, shows a marked maximum in the specific conductance curve in methylene chloride or methyl chloride (25). A plausible mechanism is a small self ionization of the titanium tetrachloride and the TiCl, 4-TiCl, ?=t TiCh+TiCfi-i=t TiCh+ + TiCls- (18) TiCfi--f RC1 R+ + TiCl " (19) alkyl chloride, followed by the displacement, of the reaction to the right by formation of the stable anion TiCl*-, thereby increasing the concentration of both cations.…”

Section: Friedel-crafts Reactionsmentioning

confidence: 99%

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Solvents of high proton availability

Kilpatrick¹

1960

J. Chem. Educ.

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Chicago 16 Solvents of High Proton Availability hn primary interest is kilieties, and some twenty-five years ago I attempted some kinetic studies in nonaqueous solvents with relatively little success; the difficulty was that we knew very little about the species present even in such common solvents as sulfuric acid. This led to some equilibrium studies in the solvent anhydrous hydrofluoric acid. Like water and sulfuric acid this solvent has a hydrogen-bonded structure and has a high dielectric constant (e = 84 at 0°C). Both HjSOj and HF differ from water in that the proton availability is higher and in addition to protonating many oxygen and nitrogen compounds they protonate some aromatic compounds to an appreciable extent (1). Sulfuric acid has the disadvantages that some organic compounds are sulfonated in it, and that its self-dissociation is too high to permit use of conductance measurements to determine equilibrium constants (2).

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Symposium on the Thermodynamics of Electrolytic Dissociation: The Effect of Dielectric Constant on Acid-Base Equilibria.

Cited by 17 publications

References 19 publications

Ionization constants of substituted benzoic acids in ethanol-water:

Ionization constants of substituted benzoic acids in ethanol-water:

Ionization constants of substituted benzoic acids in ethanol-water

Solvents of high proton availability

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