Terms Of Acid-base Properties Research Articles

Preparation, analytical Studies and application of a New Azodye Derived from Pharmaceutical Materials (Procaine Hydrochloride & Salicylic acid)

Procaine hydrochloride was used as an aromatic amine, and salicylic acid (5-[2-(diethylamino)-4-benzoateazo]-2-hydroxybenzoic acid) was used to make a new azodye derived from pharmaceutical materials ( PS ).C.H.N., H1-NMR, I.R., and visible spectroscopic techniques have also been used to characterize dye. At different pH values ( 2 - 12 ), the electronic spectra of this azo dye was investigated in terms of acid-base properties, which included defining isobestic points and determining protonation and ionization constants. The effect of different polarities of solvents on the electronic spectra was the subject of another study. The dye has been used in a variety of applications, including as an indicator for strong acid with strong base and for nitrite determination.

Preparation and characterization azo dyes derived from 4- hydroxycoumarin and studying their analytical Applications

The preparation 0f azo dyes is the subject of this research. 4-hydroxycoumarin with each ofo-amino benzoic acid (3-[o-Amino benzoic acidazo]-4-hydroxycoumarin]) (B1) and with Sulfa guanidine (3-[Sulfa guanidine azo]-4-hydroxycoumarin) (B2) were syntheses. Azo compounds were characterized by I.R, CHN,1H-NMR Elctronic and Mass spectroscopy. At various pH levels, the electronic spectra of these azo dyes were investigated in terms of acid-base properties, which includes the determination of protonation and ionization constants as well as the establishment of isobestic points. On the electronic spectra, the solvent effect was also investigated at various polarities.

Site‐Specific Acid–Base Properties of Tenoxicam

AbstractThe Hammett approach, as a new deductive tool, was introduced to characterize the otherwise inaccessible minor protonation pathway of tenoxicam (1), the non‐steroidal anti‐inflammatory drug. A total of eight compounds, constituting a systematic series of side chain‐substituted analogues of tenoxicam and piroxicam (2), were synthesized and studied in terms of acidbase properties and Hammett constants to identify the ideal replacement of the unprotonated pyridin‐2‐yl group, a key moiety in both molecules. Hammett constants of the phenyl substituents have been found to be in a linear correlation with the experimental log K values of the enolate sites, the basic moiety of the extended conjugated system in this family of piroxicam derivatives. Then, a similar correlation was observed for the analogous tenoxicam derivatives. After identifying the 2‐aza Hammett constant of the pyridin‐2‐yl group and the corresponding log K value, the site‐specific acid–base properties of tenoxicam could be quantitated. This novel method is assessed to be a fine‐tuning tool to find the ideal substituent by using analogue‐based deductive method to obtain site‐specific constants of the minor protonation/deprotonation pathway in drugs and biomolecules. The tenoxicam microconstant values indicate that the enolate moiety is of extremely low basicity (reflected by the $ \log \it k^{\rm{O}} $=3.70 and $ \log \it k_{\rm{N}}^{\rm{O}} $=1.09 values), which can, however, be interpreted in terms of the peculiar ring system and the overwhelming electron‐withdrawing effects of the adjacent heteroatoms. A diagram depicting the pH‐dependent distribution of 1 microspecies is also presented.

Comparison of the efficiency of N 2 and NH 3 plasma treatments to improve the adhesion of PP films to in situ deposited Al coatings. Study of ageing phenomena in terms of acid-base properties

This paper reports on the characteristics of polypropylene (PP) treated at two different frequencies, 70 kHz and 13.56 MHz, in two plasma atmospheres, NH 3 and N 2 plasmas. Chemical modifications created on the plasma-treated material were investigated by different complementary surface analytical techniques (X-ray photoelectron spectroscopy (XPS) and contact angle measurements), which revealed a higher reactivity of the NH 3 plasma. The incorporation of nitrogen plays an important role as revealed by the adhesion study of thermally evaporated aluminium with treated PP: the measured peel strengths were two times higher for NH 3-treated surfaces than for N 2-treated ones, with XPS measurements showing a sharper increase of N/C ratio as a function of treatment time for the former treatment. Ageing of the PP pretreated in NH 3 was also studied in terms of surface acid-base properties. The work of adhesion, calculated from contact angle measurements, showed a distinct dependence on the pH value of the test liquids and good correlations were obtained with peel test results. The basic character of the NH 3-treated PP disappears with ageing, leading to an amphoteric surface.

Magnesium oxide as a catalyst: II. Acid-base properties of the magnesium oxide surface

The surface of magnesium oxide was investigated in terms of acid-base properties. Adsorption of carbon dioxide was studied at various temperatures and pressures and was found to obey the Langmuir isotherm. Potentiometric titration studies on magnesia in pyridine as solvent revealed the presence of centers of various acidity. Infrared spectra of steamed and deuterated magnesia specimens showed the presence of free and combined hydroxyl groups at the surface of specimens ignited up to 600 °C. As the ignition temperature was raised (up to 1300 °C), the free—but not combined—hydroxyl groups disappeared.