Potentiometric Determination of the Apparent Dissociation Constants of Some Dicarboxylic Acids in Various Hydroorganic Media

Azab, Hassan A.; Ahmed, Iman T.; Mahmoud, M. R.

doi:10.1021/je960361n

Cited by 19 publications

(8 citation statements)

References 16 publications

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“…For the acetonitrile solution, however, some correction factors have to be included. The p K a values increase with increasing the concentration of the organic solvents, as was discussed in ref . The presence of acetonitrile as a cosolvent produces a stronger effect on the p K a values than other organic cosolvents studied (e.g.…”

Section: Resultsmentioning

confidence: 61%

Influence of the Solvent on the Surface-Enhanced Raman Spectra of Ruthenium(II) Bipyridyl Complexes

et al. 2005

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In the present work a new dye, [Ru(dcbpyH2)2(bpy-TPA2)](PF6)2, and the well-known (Bu4N)2[Ru(dcbpyH)2(NCS)2] complex were investigated. The electronic transitions of both dyes showed solvatochromic shifts due to specific interactions of the ligands with the solvent molecules. The surface-enhanced Raman (SER) spectra of the dyes dissolved in water, ethanol, and acetonitrile were measured in silver and gold colloidal solutions. The results demonstrate that the dyes were adsorbed on the metallic nanoparticles in different ways for different solvents. It was also found that in the gold colloid, the aqueous solutions of both dyes did not produce any SERS signal, whereas in ethanolic solution the SERS effect was very weak. Deprotonation, H-bonding, and donor-acceptor interactions seem to determine these different behaviors. Our results indicate the important role of the charge-transfer mechanism in SERS.

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Section: Resultsmentioning

confidence: 61%

Influence of the Solvent on the Surface-Enhanced Raman Spectra of Ruthenium(II) Bipyridyl Complexes

et al. 2005

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“…According to previous studies (Bates, 1964) a purely electrostatic effect on the dissociation equilibria of the zwitterionic buffers under investigation can be expressed by eq 5, where r j is the common radius of all the ions, ( 2 ) is the relative permittivity of the mixed organic solvent, n ) 2 for HA, A pairs of the charge type A 0 B -, n ) 4 for the charge type A -B 2-, and n ) 0 for the charge type A + B 0 , while 0.0128 is the reciprocal of the permittivity of water at 25 °C. The apparent dissociation constants for some dicarboxylic acids in different hydrooganic media calculated before (Azab et al, 1997) increase markedly as the permittivity decreases. The pK a2 * for zwitterionic buffers, however, is not, as might be expressed from eq 5, unaffected by a change in the permittivity.…”

Section: Resultsmentioning

confidence: 94%

Medium Effect on the Apparent Second Stage Dissociation Constants of Some Zwitterionic Buffers for Physiological Research in Various Water + Organic Solvent Mixtures

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1999

J. Chem. Eng. Data

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The apparent second stage dissociation constants of piperazine-N,N-bis[2-hydroxypropanesulfonicacid] (POPSO), N-[2-hydroxyethy1]piperazine-N′-3-propane sulfonic acid (HEPPS), 2-[N-cyclohexylamino]ethanesulfonic acid (CHES) and mono[tris(hydroxymethyl)aminomethane] phosphate (Trizma) were determined at (25.0 ( 0.1) °C and I ) 0.1 mol dm -3 (KNO 3 ) by potentiometric pH titration in pure water and different hydroorganic solvent media. The organic solvents used were methanol and ethanol as amphiprotic hydrogen bond acceptor-donor (HBA-D) solvents, N,N-dimethylformamide (DMF), dimethy1 sulfoxide, acetone, and dioxane as hydrogen bond acceptor solvents, and acetonitrile as an HBA-HBD solvent. The ESAB2M computer program was used to refine the initial estimates of the apparent secondstage dissociation constants of the four zwitterionic buffers studied. pk a2 * values change with increasing organic content of the solvent mixture. The results obtained are discussed in terms of average macroscopic properties of the mixed solvents. The implications of the results with regard to specific solute-solvent interacions, particularly stabilization of zwitterionic species, are discussed. The effects of coorganic solvents on the acid dissociation equilibria have been interpreted using solvatochromic quantitative values of Kamlet-Taft hydrogen bond acidity and basicity (R, β) and dipolarity-polarizability π* of the solvent.

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“…(3) Azab (Azab et al, 1997) increase markedly as the permittivity decreases. The pK a2 for zwitterionic buffers usually increases or decreases somewhat with increasing the organic solvent concentration.…”

Section: Mops Ampso and Heppso Possess The Following Zwitterionic Str...mentioning

confidence: 98%

Apparent Second-Stage Dissociation Constants of Some Zwitterionic Buffers for Biochemical and Physiological Research in Various Hydroorganic Media

1998

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The apparent second-stage dissociation constants of 3-(N-morpholino)propanesulfonic acid, 3-[(1,1dimethyl-2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, and N-(2-hydroxyethyl)piperazine-N′-(2-hydroxypropanesulfonic acid) were determined at (25.0 ( 0.1) °C and I ) 0.1 mol dm -3 (KNO 3 ) by potentiometric pH titration in pure water and different hydroorganic solvent media. The organic solvents used were methanol, ethanol as amphiprotic hydrogen bond acceptor-donor (HBA-D) solvents, N,Ndimethylformamide, dimethyl sulfoxide, acetone, dioxane as hydrogen bond acceptor solvents, and acetonitrile as (HBA-HBD) solvent. The ESAB2M computer program was used to refine the initial estimates of the apparent second-stage dissociation constants of the three zwitterionic buffers studied. pK a2 * values change with increasing organic content of the solvent mixture. The results obtained are discussed in terms of average macroscopic properties of the mixed solvents. The implications of the results with regard to specific solute-solvent interactions, particularly stabilization of zwitterionic species, are discussed. The effects of coorganic solvents on the acid dissociation equilibria have been interpreted using solvatochromic quantitative values of Kamlet-Taft hydrogen bond acidity and basicity (R, β) and dipolarity-polarizability π * of the solvent.

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Potentiometric Determination of the Apparent Dissociation Constants of Some Dicarboxylic Acids in Various Hydroorganic Media

Cited by 19 publications

References 16 publications

Influence of the Solvent on the Surface-Enhanced Raman Spectra of Ruthenium(II) Bipyridyl Complexes

Influence of the Solvent on the Surface-Enhanced Raman Spectra of Ruthenium(II) Bipyridyl Complexes

Medium Effect on the Apparent Second Stage Dissociation Constants of Some Zwitterionic Buffers for Physiological Research in Various Water + Organic Solvent Mixtures

Apparent Second-Stage Dissociation Constants of Some Zwitterionic Buffers for Biochemical and Physiological Research in Various Hydroorganic Media

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