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  • 1
    Electronic Resource
    Electronic Resource
    Dissociation of acetic acid in 50 mass % ethylene carbonate-water from 20 to 55°C (1975)
    Springer
    Journal of solution chemistry 4 (1975), S. 1033-1039 
    Details
    ISSN: 1572-8927
    Keywords: Acetic acid ; acidic dissociation ; dissociation constant ; ethylene carbonate ; ionization ; nonaqueous solvents ; solute-solvent effects ; weak acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dissociation constant of acetic acid in 50 mass % ethylene carbonate-water solvents has been determined at eight temperatures from 20 to 55°C by emf measurements of cells without liquid-junction containing hydrogen electrodes and silver-silver chloride electrodes. Acetic acid is weaker in the mixed solvent than in pure water. At 25°C, pK is 5.645 as compared with 4.756 in water, in spite of the fact that the dielectric constants of the two media do not differ materially. Standard changes in Gibbs energy, enthalpy, entropy, and heat capacity for the dissociation processes at 25°C were evaluated. The decrease in acidic strength when ethylene carbonate is added to the water medium appears to be largely the results of a destabilization of the two ionic species, especially a partial desolvation of the hydrogen ion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01074745
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  • 2
    Electronic Resource
    Electronic Resource
    Solvent effects on acid-base behavior: Five uncharged acids in water-sulfolane solvents (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 213-222 
    Details
    ISSN: 1572-8927
    Keywords: Acidic dissociation ; dissociation constants ; ionization ; mixed solvents ; solute-solvent effects ; solvent effects ; sulfolane-water solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An electrometric titration method utilizing glass electrodes and silver-silver bromide electrodes in a cell without liquid junction has been applied to a determination of the dissociation constants of five uncharged weak acids (HA) in four mixtures of water and sulfolane (tetramethylene sulfone) at 25°C. The acids studied were monochloroacetic, formic, benzoic, and acetic acids andp-nitrophenol, and the mole fractions (x 2) of sulfolane in the mixed solvents were 0.2, 0.4, 0.6, and 0.8. All measurements were made at a constant ionic strength of 0.02 mole-kg−1 in a solution containing NaBr at a molality of 0.01 mole-kg−1. The cell was standardized by measurements of HClO4 at molalities from 0.002 to 0.01 mole-kg−1 and, in subsequent measurements, a solution of NaA was titrated with HClO4. To obtain the thermodynamic pK, an activity correction derived from the Debye-Hückel theory was applied. The pK of all five acids was found to vary linearly withx 2 in the range 0 to 0.8. By comparison of data for acetic acid in water-methanol, water-dioxane, and water-sulfolane solvents, it was shown that the results are consistent with the known properties of sulfolane (low acidity, basicity, and solvating power), but the linear variation of pK with solvent composition remains unexplained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654338
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  • 3
    Electronic Resource
    Electronic Resource
    Dissociation constant of acetic acid in N-methylpropionamide from 5 to 55°C and related thermodynamic quantities (1972)
    Springer
    Journal of solution chemistry 1 (1972), S. 507-516 
    Details
    ISSN: 1572-8927
    Keywords: Acetic acid ; dissociation constant ; N methylpropionamide ; nonaqueous solvents ; solute-solvent interactions ; weak acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dissociation constant of acetic acid in N-methylpropionamide (NMP) has been determined at 11 temperatures from 5 to 55°C by measurement of the electromotive force of cells without liquid junction containing hydrogen gas electrodes and silver-silver chloride electrodes. The pK at 25°C was found to be 7.995 (molal scale) as compared with 4.756 in water; thus, acetic acid is much weaker in NMP than in water despite the higher dielectric constant of the nonaqueous solvent (176 as compared with 78.3 at 25°C). The standard changes of enthalpy and entropy for the dissociation of acetic acid were calculated from the temperature coefficient of pK, and thermodynamic functions for the transfer dissociation process were obtained. The weakness of acetic acid in NMP is discussed in terms of electrostatic effects and solute-solvent interactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651727
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  • 4
    Electronic Resource
    Electronic Resource
    Thermodynamics of the dissociation of morpholinium ion in seawater from 5 to 40°C (1982)
    Springer
    Journal of solution chemistry 11 (1982), S. 79-89 
    Details
    ISSN: 1572-8927
    Keywords: Acidic dissociation ; dissociation constant ; ion-ion interactions ; ionization ; morpholinium ion ; salt effect ; seawater ; thermodynamics of dissociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dissociation constant of morpholinium ion has been determined in five synthetic seawaters at eight temperatures from 5 to 40°C. The seawater solvents contained NaCl, MgCl2, Na2SO4, CaCl2, and KCl in amounts corresponding to salinities of approximately 10, 20, 30, 35, and 40‰ (parts per thousand) and ionic strengths ranging from 0.2 to 0.8 mol-kg−1. Electromotive-force measurements of cells without liquid junction, with hydrogen gas electrodes and Ag/AgCl electrodes, were used to derive the dissociation constant and associated changes of enthalpy, entropy, and heat capacity for the dissociation equilibrium. The pK values over the range of salinity S and thermodynamic temperature T studied are given by the equation $$\begin{gathered} pK = (1396.58 + 1.822S)/T - 2.14236 InT + 16.0138 + 0.001912S \hfill \\ - 9.722 \times 10^{ - 5} S^2 + 1.025 \times 10^{ - 6} S^3 \hfill \\ \end{gathered}$$ At a salinity of 35‰, corresponding to ‘normal seawater’, pK is higher by 0.206 at 25°C than in the water solvent, while ΔHo is increased by 292 cal-mol−1 and both ΔSo and ΔC p o are substantially unchanged. The buffer composed of 0.04 molal morpholinium chloride and 0.04 molal morpholine is useful for pH control in synthetic seawater media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01036376
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  • 5
    Electronic Resource
    Electronic Resource
    Thermodynamics of the dissociation of 2-aminopyridinium ion in synthetic seawater and a standard for pH in marine systems (1986)
    Springer
    Journal of solution chemistry 15 (1986), S. 891-901 
    Details
    ISSN: 1572-8927
    Keywords: Acidic dissociation ; 2-aminopyridine ; dissociation constant ; hydrogen ion ; ionization ; pH ; salt effect ; seawater ; thermodynamics of dissociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Buffer solutions composed of 2-aminopyridinium chloride and 2-aminopyridine in synthetic seawater are useful as a supplement to buffers of ‘Tris’ (pH 8.2) and ‘Bis’ (pH 8.8) in standardizing measurements of hydrogen ion concentration (pm H or pH(SWS)) in oceanography. The dissociation constant of 2-amino-pyridinium ion over the range of salinities (S) from 30 to 40 has now been determined from the emf of cells without liquid junction at eight temperatures (T) from 278.15 to 313.15 K. The results fit the equation pK=2498.31/T−15.3274+2.4050 lnT+S(0.012928−2.9417×10−5T) with a standard deviation of 0.0023. Thermodynamic constants for the dissociation process and standard reference values of pm H and pH(SWS) were derived from the data. The pm H of the buffer consisting of 2-aminopyridinium chloride and 2-aminopyridine (each 0.04 molal) in synthetic seawater of salinity 35 varies from 7.356 at 278.15 K to 6.601 at 313.15 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646030
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  • 6
    Electronic Resource
    Electronic Resource
    Solute-solvent effects in the acidic dissociation of the ampholyte N-tris(hydroxymethyl)methylglycine (“tricine”) in 50 mass % methanol-water solvent (1974)
    Springer
    Journal of solution chemistry 3 (1974), S. 905-916 
    Details
    ISSN: 1572-8927
    Keywords: Acidic dissociation ; ampholyte dissociation ; dissociation constants ; ionization ; methanol-water solvents ; solute-solvent effects ; N-Tris(hydroxymethyl)methylglycine (“tricine”) ; zwitterions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The pK values for the two acidic dissociation steps of the ampholyte N-tris-(hydroxymethyl)methylglycine (“tricine”) in 50 mass % methanol-water solvent have been determined by emf measurements of cells of the type Pt|H2(g, 1 atm), tricine buffer, Br−, AgBr|Ag over the range 5 to 50°C (pK 1)and 5 to 60°C (pK 2).The standard thermodynamic quantities ΔHo, ΔSo, and ΔC p o for the two dissociation processes have been derived and are compared with the corresponding values for tricine and the parent glycine in water and with those for other acids in 50 mass % methanol-water solvent. Both tricine and protonated tricine become weaker acids when methanol is added to the aqueous solvent. It appears that a strong stabilization of the zwitterion in water is responsible for this behavior. This conclusion is supported by comparing the changes in entropy and heat capacity for the dissociation of tricine with the values of these quantities for the dissociation of “model” acids of simple structure, such as ammonium ion and acetic acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647944
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  • 7
    Electronic Resource
    Electronic Resource
    Solute-solvent interactions in acid-base dissociation: nine protonated nitrogen bases in water-DMSO solvents (1975)
    Springer
    Journal of solution chemistry 4 (1975), S. 817-829 
    Details
    ISSN: 1572-8927
    Keywords: Acidic dissociation ; bases ; dissociation constants ; DMSO-water solvents ; ionization ; mixed solvents ; solute-solvent effects ; solvent effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A titration method utilizing glass electrodes and silver-silver chloride electrodes in a cell without liquid junction has been used to determine the acidic dissociation constants at 15, 25, and 35°C of nine protonated nitrogen bases in mixtures of water and dimethyl sulfoxide (DMSO). The mole fraction of DMSO in the mixed solvents was 0.2, 0.4, 0.6, and 0.8. The cell was calibrated with HCl (molality=0.01 mole-kg−1) in the mixed solvents, and the ionic strength and chloride molality remained substantially unchanged during the titration with added base. This method minimizes the errors resulting from the formation of AgCl 2 − in the media rich in DMSO. The pK a of all the protonated bases passes through a minimum at a solvent composition close to that at which H2O-DMSO mixtures display a maximum solvent structure. The results are discussed in terms of the preferential solvation of ions by the two types of solvent molecules. They are consistent with the hypothesis that increased solvent structure is accompanied by increased desolvation of the cation acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00650538
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  • 8
    Electronic Resource
    Electronic Resource
    Solute-solvent interactions in acid-base dissociation: Seven protonated nitrogen bases in water-N-methyl-2-pyrrolidinone solvents (1976)
    Springer
    Journal of solution chemistry 5 (1976), S. 325-332 
    Details
    ISSN: 1572-8927
    Keywords: Acidic dissociation ; bases ; dissociation constants ; ionization ; N-methyl-2-pyrrolidinone-water solvents ; mixed solvents ; solute-solvent effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Acidic dissociation constants of seven protonated nitrogen bases, namely “Bis-tris”, 2-aminopyridine, “Tris”, morpholine, 2-amino-2-methyl-1,3-propanediol,n-butylamine, andt-butylamine, have been determined at 15, 25, and 35° C in mixtures of water andN-methyl-2-pyrrolidinone (NM2Py). The mole fractions of cosolvent were 0.2, 0.4, 0.6, and 0.8. Glass and silver-silver chloride electrodes were used in a cell without liquid junction, and both the ionic strength and molality of chloride ion remained substantially constant in all of the measurements. The pK a of all the protonated bases decreases initially and passes through a minimum as the aqueous solvent is enriched with NM2Py. The order of acidic strengths is the same as in the H2O-dimethyl sulfoxide (DMSO) solvent system, but the pK a values are all lower by up to 2 units. NM2Py appears to be a more basic solvent than DMSO or H2O.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647197
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  • 9
    Electronic Resource
    Electronic Resource
    The solvent effect of methanol on the dissociation of Bis·H+ from 10 to 40°C (1981)
    Springer
    Journal of solution chemistry 10 (1981), S. 155-162 
    Details
    ISSN: 1572-8927
    Keywords: Acidic dissociation ; basic dissociation ; Bis ; dissociation constant ; ionization constant ; methanol ; solute-solvent effects ; solvent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The solvent effect on the acidic dissociation of the protonated base tris(hydroxymethyl)aminomethane (Tris) has been studied in aqueous mixtures of several organic constituents with qualitatively similar results. The dissociation constant of protonated 2-amino-2-methyl-1,3-propanediol (Bis), the analog of Tris with two hydroxy groups, has now been determined in 50 mass % methanol by emf measurements of cells without liquid junction in the temperature range 10 to 40°C. The conventional treatment of the data indicated abnormally low values for the activity coefficient of BisHCl, but an alternate method of calculation with allowance for ion pairing provided no advantage. The pKa in the range from T=283.15 to 313.15 K is given by $$pK_a = 3755.63/T - 24.5127 + 3.56855 In T$$ with a standard deviation of 0.0006 at the seven temperatures. Thermodynamic quantities for the dissociation process and corresponding quantities for the transfer from water to 50 mass % methanol were derived. The implications of the results in terms of selective solute-solvent stabilization are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653092
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  • 10
    Electronic Resource
    Electronic Resource
    Thermodynamics of the dissociation of Bis H+ in seawater from 5 to 40°C (1981)
    Springer
    Journal of solution chemistry 10 (1981), S. 269-279 
    Details
    ISSN: 1572-8927
    Keywords: Acidic dissociation ; Bis dissociation ; dissociation constant ; ion-ion interactions ; ionization ; seawater ; thermodynamics of dissociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electromotive-force measurements of cells without transference were used to determine the dissociation constant of the protonated form of the weak base 2-amino-2-methyl-1, 3-propanediol (Bis) in synthetic seawaters corresponding to salinities of 20, 35, and 45‰. Hydrogen electrodes and silver-silver chloride electrodes were used, together with standard potentials determined in an earlier investigation. The pK increases in linear fashion with the salinity (S) of the medium, for values of S from 0 to 45‰. The solvent effect is given by 8.802+0.00378S at 25°C with a mean deviation of 0.001. The medium effect of seawater on ΔH° at 25°C is less than 200 cal-mol−1 and less than 0.2 cal-oK-mol−1 on ΔS°.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645016
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