• Korean Journal of Soil Science and Fertilizer
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• v.29 no.4
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• pp.328-335
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• 1996

Using literature data on back titration curves of some typical Korean soils and minerals we calculated the distribution functions of aparent surface dissociation constants for these materials using site heterogeneity approach. The studied materials exhibited broad range of apparent surface dissociation constants. The dominant surface sites for all samples appeared to be very weakly acidic. However, the relative amounts of surface sites differed among particular materials.

• Archives of Pharmacal Research
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• v.16 no.3
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• pp.180-185
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• 1993

The acid dissociation constants of certain Schiff bases derived from isatin with p-substituted benzoyl hydrazines and somee amino acids of glycine, $\beta$-and $\alpha$-alanine, valine, $\beta$-phenyl-$\alpha$-alanine and anthranilic acid have been detemined potentiometrically at different temperatures in different aquo-organic solvent mixtures (ethnol, dioxane, dimethyl formamide, methanol, acetone and tetrahydrofurance). The pKa values were demonstrated on the light of the different electornic and steric effects of the substituents and the sovlent characteristics. In all the mixed media used, ionization of the compounds decreased by increasing the mole fraction of the organic cosolvent. Theemodynamic parameters $(\Delta{H}^\circ,\;\Delta{G}^\circ,\;\Delta{S}^\circ)$ were evaluated. The structural effects of the investigated compounds on these parameters were reported and discussed.

• Journal of the Korean Chemical Society
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• v.16 no.6
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• pp.369-372
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• 1972

The dissociation constants of dibasic carboxylic acids $(HOOC(CH_2)_nCOOH$, n = 0~4] in methanol, N, N-dimethylformamide and acetonitrile have been determined by the potentiometric method with a glass electrode. The difference between over-all dissociation constants in each other solvent is found to be of the same order of magnitude, and the $K_1/K_2$ ratios in aprotic dimethylformamide and acetonitrile are much greater than those in protic methanol and water.

• Journal of Environmental Science International
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• v.15 no.8
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• pp.799-809
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• 2006

Hydrobromic acid salts of new N, N, O tridentate ligands containing phenol, 2-[(2-Methylamino- ethyl- amino)-methyl]-phenol(H-MMP. 2HBr), 5-Bromo-2-[(2-Methylamino-ethylamino)-methyl]-phenol (Br- MMP. 2HBr), 5-Chloro-2-[(2-Methylamino-ethylamino)-methyl]-phenol(Cl-MMP. 2HBr), 5-Methyl-2-[(2-Methylamino-ethylamino)-methyl]-phenol(Me-MMP. 2HBr), 5-Methoxy-2-I(2-Methylamino-ethylamino)- methyl]-phenol(MeO- MMP. 2HBr) and. 1-[(2-Methylamino-ethylamino)- methyl]-naphthalen-2-ol(Nap- MMP. 2HBr) were synthesized. The synthesized ligands were confirmed by C. H. N. atomic analysis, UV-visible and IR spectroscopies, $^1$H NMR, $^{13}$C NMR and mass analysis. The potentiometry study revealed that the proton dissociation constants(logK$_n^H$) of the synthesized ligands and stability constants (logK$_{ML}$, logK$_{LM2}$) of transition metal complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions occurred in three steps and the order of the calculated overall proton dissociation constants(log$\beta_p$) and stability constants (logK$_{ML}$) of ligands was Br-MMP. 2HBr < Cl-MMP 2HBr < H-MMP. 2HBr < Nap-MMP. 2HBr < Me-MMP. 2HBr < MeO-MMP. 2HBr. The order showed a similar trend to that of Hammett substituent constants($\delta_p$). The synthesized ligands usually form 2:1(ML$_2$) complexes with transition metal ions. The order of the stability constants of each transition metal ions was Co(II) < Ni(II) < Cu(II) ;> Zn(II) ;> Cd(II) ;> Pb(II).

• Journal of Environmental Science International
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• v.13 no.9
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• pp.835-843
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• 2004

N,N-bis(2-salicylaldehyde)dipropylenetriamine(5- Hsaldipn), N,N-bis( 5-bromosalicyl-aldehyde) dipropylenetriamine (5-Brsaldipn), N,N-bis(5-chlorosalicy laldehyde )dipropylene-triamine(5-Clsaldipn), N,N-bis(2-hydroxy- $5-methoxy-benzaldehyde)dipropylenetriamine(5-OCH_3saldipn)$ and N,N-bis (2-hydroxy-5-nitrobenzaldehyde)dipropylenetriamine $(5-NO_2saldipn)$ were synthesized and characterized by elemental analysis, infrared spectrometry, NMR spectrometry and mass spectrometry. Their proton dissociation constants were determined in 70% dioxane/30% water solution by potentiometric. Stability constants of the complexes between these ligands and the metal ions such as Cu(II), Ni(II) and Zn(II) were measured in dimethyl sulfoxide by a polarographic method. Stability constants for the ligands were in the order of $5-OCH_3$ > 5-H > 5-Br > 5-Cl > $5-NO_2$ saldipn. Enthalpy and entropy changes were obtained in negative values.

• Textile Coloration and Finishing
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• v.5 no.3
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• pp.216-220
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• 1993

Dissociation constants and heat of dissociation of dimers of 3, 3'-diethyl-thiacarbocyanine dye(Dye 2) have been studied. At $10~40^{\circ}C$, absorption spectra of 2 vol% aqueous ethanol solutions of Dye 2 showed monomer and dimer bands. From the temperature dependence of monomer absorbance, dissociation constants K and ${\Delta}H$ were estimated to be $6.2(10^{\circ}C)-10.6(40^{\circ}C)mon/\ell$ and 3kcal/mol, respectively. These K valus are about one half of those for 3,3'-diethyl-2,2'-cyanine dye with one methine carbon, indication a higher dimer stability than that of 3,3-diethyl-2,2'-cyanine dye.

• Journal of the Korean Chemical Society
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• v.35 no.2
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• pp.105-110
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• 1991

The dissociation constants of valine and norvaline in aqueous solution were measured by conductometric method in various temperatures and pressures. The properties of the dissociation reaction were discussed in term of the thermodynamic properties of reaction. These substituted effects on the dissociation reaction were discussed on the points of Hammett relation and net charge of the O and N-atom calculated from CNDO/2 method respectively.

• Journal of Environmental Science International
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• v.18 no.7
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• pp.735-746
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• 2009

Hydrochloric acid salt of a new $N_2O_3$ pentadentate ligand, N,N'-Bis(2-Hydroxybenzyl)-1,3-diamino-2-propanol(H-BHDP 2HCl) was synthesized. Br-BHDP 2HCl, CI-BHDP 2HCl, $CH_3-BHDP$ 2HCl and $CH_3O$-BHDP 2HCl having Br, Cl, $CH_3$ and $CH_3O$ substituents at 5-position of the phenol group of H-BHDP 2HCl were also synthesized. The potentiometry study in aqueous solution revealed that the proton dissociations of the synthesized ligands occurred in four steps and their order of the calculated overall proton dissociation constants($log{\beta}_p$) was Br-BHDP < Cl-BHDP < H-BHDP < $CH_3O-BHDP$ < $CH_3-BHDP$. The order showed a similar trend to that of Hammett substituent constants(${\delta}_p$). The order of the stability constants($logK_{ML}$) was Co(II) < Ni(II) < Cu(II) < Zn(II) < Cd(II) < Pb(II). The order in their stability constants ($logK_{ML}$) of each transition metal complex agreed with that of the overall proton dissociation constants ($log{\beta}_p$).

• Journal of the Korean Chemical Society
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• v.10 no.3
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• pp.114-118
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• 1966

The glass electrode was empirically calibrated in dioxane-and ethanol-water mixed solvents, by means of which the pH-meter reading could be converted to stoichiometric hydrogen ion concentration. By the potentiometric titration method, the thermodynamic dissociation constants of hydrogen cupferrate (HCup) with variations of ionic concentration in aqueous solution were determined, and by the extrapolation of the constants the new thermodynamic $pK_a$ value, 3.980${\pm}$0.006, at zero ional concentration was obtained. The thermodynamic dissociation constants of HCup in dioxane-and ethanol-water solution were also potentiometrically determined with the changes in composition of organic solvents at 0.01 and 0.05 of the ionic strength(${mu}$) and 25 $^{\circ}C$. The empirical formula of the constants with mole fraction(n) of the organic solvent are as follow: Dioxane-water solution. $pK_a$= 12.96n + 4.10 at ${\mu}$ = 0.01, n = 0.0228∼0.171 $pK_a$= 12.05n + 4.23 at ${\mu}$ = 0.05, n= 0.0228∼0.171 Ethanol-water solution, $pK_a$= 4.0ln + 4.26 at ${\mu}$= 0.01, n= 0.0395∼0.262 $pK_a$= 3.83n + 4.34 at ${\mu}$= 0.05, n= 0.0395∼0.262

• Journal of the Korean Chemical Society
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• v.12 no.1
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• pp.1-3
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• 1968

New chelating ligands, thiocatechol and p-chlorothiocatechol, have been synthesized and the acid dissociation constants were determined by potentiometric method in 50% dioxane-water; $pK_1 \;and\; pK_2$ were 7.28, 10.97 for thiocatechol and 6.37, 10.22 for p-chlorothiocatechol, respectively. Color reactions with various metal ions were studied. It was found that the above ligands are specific for Bi(III), Mo(VI) and W(VI) as an analytical reagent.