Spectrophotometric Study of Acid-Base Equilibria in Non-Aqueous Solvents

The equilibrium constants for the reaction of 2,6-dichloro-4- -nitrophenol, 2,6-dinitrophenol, 2,5-dinitrophenol and 2,4-dinitrophenol with some aliphatic amines of different structures have been determined spectrophotometrically in chlorobenzene, ethyl acetate and carbon tetrachloride as solvents. The data show that such reactions in inert solvents lead essentially to ion-pairs of the type BH+ ... A- where, HA and B represent the phenol and ·amine molecule, respectively. This conclusions was found to be in agreement with that obtained by other workers. In chlorobenzene as a solvent, the basic strengths fall in the order mono < di- < tri-n- . -butyl amine, while in ethyl acetate the order of basic strengths becomes: mono-> di-> tri-n-butyl amine. These results are discussed from the point of view of solvation as an important role in the determination of the relative strengths of butylamines, as well as the extent to which dinitrophenols are affected by chelation between the phenolic OH and ortho-nitro group. However, in chlorobenzene and ethyl acetate as solvents, the relative basic strengths of pyridine and aniline derivatives remain independent of the solvent when bromophenol blue is used as a reference acid. The of KBH+A- values for aniline derivatives proved to be more suitable for judging the effect of the substituent than the basic strength in aqueous solution

Solubility of Tris(hydroxymethyl)aminomethane in Water + Methanol +1-Propanol Mixtures at Various Temperatures

Article on the solubility of tris(hydroxymethyl)aminomethane in water + methanol + 1-propanol mixtures at various temperatures

Potentiometric Study of Acid-Base Interactions in Acetonitrile

The potentiometric titration curves of acids of different types were studied using piperidine and tetra-n-butylammonium hydroxide, (Bu4NOH), as titrants in acetonitrile (AN) as solvent. The effect of methanol addition on the shape of the potentiometric curves was discussed. The dissociation constants, KHA, and homoconjugation constants, KHA2- , of some acids were potentiometrically determined in AN. No exact correlation was found between KHA of the studied acids in AN and the corresponding values-in water. It was concluded that the acid characteristics, its anion properties, and the solvent . type are the most important factors determining KHA2-. The heteroconjugation constants, KAHA,- of some anions with different acids were also determined. K AHAc values for some substituted benzoic acids with reference to acetate ion were found to follow a linear free energy relationship with Hammett substituent constants

Solubility Determination of Tris(hydroxymethyl)aminomethane in Water + Methanol Mixtures at Various Temperatures Using a Laser Monitoring Technique

Article on solubility determination of tris(hydroxymethyl)aminomethane in water + methanol mixtures at various temperatures using a laser monitoring technique