Effects of Solvent Polarity on the Acid Dissociation Constants of Benzoic Acids

Rubino, Joseph T.; Berryhill, William S.

doi:10.1002/jps.2600750217

Cited by 43 publications

(12 citation statements)

References 10 publications

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“…The effect of DMSO co-solvent on the pK a for 1 is in very good agreement with the work of Rubino and Berryhill (22). Those authors attributed the effects of the co-solvent on the pK a to both electrostatic and non-electrostatic medium effects.…”

Section: Methodssupporting

confidence: 89%

Acid Dissociation Constants of Bilirubin and Related Carboxylic Acid Compounds in Bile Salt Solutions

Kurtin

Enz

Dunsmoor

et al. 2000

Archives of Biochemistry and Biophysics

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Section: Methodssupporting

confidence: 89%

Acid Dissociation Constants of Bilirubin and Related Carboxylic Acid Compounds in Bile Salt Solutions

Kurtin

Enz

Dunsmoor

et al. 2000

Archives of Biochemistry and Biophysics

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“…Moreover, the same spectra of TPPS 2a , mTHPP and mTHPC in methanol/PBS mixture (1:1) as well as in Triton X-100 containing PBS (0.6%) were taken for comparison. In general there is an influence of solvent composition on the acid dissociation constant (22); thus, the purpose of the solvent mixture application was to check the differences in the shape of titration curves in relation to the number of inflection points, not their localization.…”

Section: Resultsmentioning

confidence: 99%

pH-Dependent Spectral Properties of HpIX, TPPS2a, mTHPP and mTHPC¶

Čunderlı́ková¹,

Bjørklund²,

Pettersen³

et al. 2007

Photochemistry and Photobiology

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Lower extracellular pH in tumors as compared to normal tissues has been proposed to be a factor contributing to the tumor selective uptake of several photosensitizers. Therefore, the pH dependence of absorption and fluorescence spectral properties of four different drugs relevant for photodynamic therapy (hematoporphyrin IX [HpIX], disulfonated meso‐tetraphenylporphine [TPPS2a], meso‐tetra(3‐hydroxyphenyl)porphine [mTHPP] and meso‐tetra(3‐hydroxyphenyl)chlorin [mTHPC]) has been examined. Spectral analysis of the dyes dissolved in phosphate buffered saline (PBS) indicates pH‐dependent modification in the physiologically important region (6.0–8.0) only in the case of HpIX. This modification is probably related to the protonation of carboxylic groups. Spectral changes of HpIX in PBS observed at acidic pH values <5, as well as those of the rest of the drugs (inflection points of titration curves occurred at about 5.1, 3.8 and 2.4 for TPPS2a, mTHPP and mTHPC, respectively), are likely to be due to the protonation of imino nitrogens. The tumor localizing properties of mTHPP and mTHPC reported in the literature appear to be due to factors other than pH‐dependent changes in the lipophilicity of the drugs.

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“…where l b,w = e 2 4πε w ε 0 k B T = 0.714 nm is the Bjerrum length in water at 25 • C, a H + = 0.122 nm is the radius of the hydronium ion, 35 and ε w = 78.3 is the dielectric constant of water. In EtOH, for example, the estimated shift ∆pK a,s = 2.8 implies that the pK a of the SiOH group would be expected to lie around 10.3.…”

Section: A Comparing Experimental Measurements With a Charge Regulatmentioning

confidence: 99%

Measured electrical charge of SiO2 in polar and nonpolar media

Kokot

Bespalova

Krishnan

2016

The Journal of Chemical Physics

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We present measurements of the net electrical surface charge of silicon dioxide (SiO2) in contact with solvents of dielectric constants between 5 and 80. Our experimental approach relies on observing the thermal motion of single silica particles confined in an electrostatic fluidic trap created by SiO2 surfaces. We compare the experimentally measured functional form of the trapping potential with that from free energy calculations and thereby determine the net surface charge in the system. Our findings clearly demonstrate that contrary to popular perception, even in the absence of surfactants, the net electrical charge of ionizable surfaces in contact with apolar solvents can be large enough to lead to significant repulsive forces. A charge regulation model for SiO2 surfaces with a single tunable parameter explains our measurements. This model may find general applicability in estimating the net charge of ionizable surfaces, given system parameters such as the dissociation or association constants of the ionizable groups and the pH, ionic strength, and dielectric constant of the solvent phase. We present measurements of the net electrical surface charge of silicon dioxide (SiO 2 ) in contact with solvents of dielectric constants between 5 and 80. Our experimental approach relies on observing the thermal motion of single silica particles confined in an electrostatic fluidic trap created by SiO 2 surfaces. We compare the experimentally measured functional form of the trapping potential with that from free energy calculations and thereby determine the net surface charge in the system. Our findings clearly demonstrate that contrary to popular perception, even in the absence of surfactants, the net electrical charge of ionizable surfaces in contact with apolar solvents can be large enough to lead to significant repulsive forces. A charge regulation model for SiO 2 surfaces with a single tunable parameter explains our measurements. This model may find general applicability in estimating the net charge of ionizable surfaces, given system parameters such as the dissociation or association constants of the ionizable groups and the pH, ionic strength, and dielectric constant of the solvent phase. Published by AIP Publishing. [http://dx

show abstract

Effects of Solvent Polarity on the Acid Dissociation Constants of Benzoic Acids

Cited by 43 publications

References 10 publications

Acid Dissociation Constants of Bilirubin and Related Carboxylic Acid Compounds in Bile Salt Solutions

Acid Dissociation Constants of Bilirubin and Related Carboxylic Acid Compounds in Bile Salt Solutions

pH-Dependent Spectral Properties of HpIX, TPPS2a, mTHPP and mTHPC¶

Measured electrical charge of SiO2 in polar and nonpolar media

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