Comparison of pK_á Values Determined by Electrometric Titration and Ultraviolet Absorption Methods

Effects of Double-Chained Cationic Surfactants n-Dimethyldialkylammoniums on Skin Permeation of Benzoic Acid through Excised Guinea Pig Dorsal Skin: Comparison of Their Enhancement Effects with Hemolytic Effects on Erythrocytes.

“…The pH value in the donor suspension was 2.6, which was significantly lower than the pK a value of benzoic acid (4.2). 10) One hundred fifty microliters of sample was taken from the receiver cells periodically over a maximum period of 9 h, then diluted 20 times or more with PBS and analyzed by UV absorbance at 224 nm. Solubilized components from skin did not interfere with the UV absorbance.…”

Synthesis and Properties of Targeted Radioisotope Carriers Based on Poly(Acrylic Acid) Nanogels

“…Comparing the spectrum of p-toluidine and the coupling products, one can see a certain shift in the bands. The pH of all samples was set as a value above the p-toluidine p K a = 5.1 [ 85 ]; hence, these differences did not originate from varying pH values, but rather from differences in the electronic structure between the starting amine and resulting amide, which may have been particularly pronounced in this system due to the aromatic character of the substituent. The peak shifts in the coupling products spectra made it impossible to quantify the content of p-toluidine.…”

Microwaves and Aqueous Solvents Promote the Reaction of Poorly Nucleophilic Anilines with a Zincke Salt

“…This study showed a good correlation between the yield of the reaction and the p K a of the conjugate acid of the considered aniline derivative (Figure ). − In our conditions, compounds associated with p K a superior to 3.75 gave the corresponding salt in quantitative yields. Conversely, aniline derivatives associated with p K a inferior to 2.75, characterized by the electronic deactivation of the nitrogen atom, eventually associated with a steric hindrance, gave the expected salts in low yields of about 20% maximum.…”