An Oxidation Study of Phthalimide-Derived Hydroxylactams

A systematic study of the oxidation of 3-hydroxy-2-substituted isoindolin-1-ones (hydroxylactams) and their conversion to the corresponding phthalimides was undertaken using three oxidants. Of special interest was the introduction of nickel peroxide (NiO2) as an oxidation system for hydroxylactams and comparison of its performance with the commonly used pyridinium chlorochromate (PCC) and iodoxybenzoic acid (IBX) reagents. Using a range of hydroxylactams, optimal conversions of these substrates to the corresponding imides was achieved with 50 equivalents of freshly prepared NiO2 in refluxing toluene over 5–32 h reaction times. By comparison, oxidations of the same substrates using PCC/silica gel (three equivalents) and IBX (three equivalents) required oxidation times of 1–3 h for full conversion but required lengthier purification. While nominal amounts (~25 mg) of substrate hydroxylactams were used to ascertain conversion, scale-up procedures using all three methods gave good to excellent isolated yields of imides.

Design and Microwave-Assisted Synthesis of TiO2-Lanthanides Systems and Evaluation of Photocatalytic Activity under UV-LED Light Irradiation

The TiO2-Eu and TiO2-La systems were successfully synthesized using the microwave method. Based on the results of X-ray diffraction analysis, it was found that regardless of the analyzed systems, two crystal structures were noted for the obtained samples: anatase and rutile. The analysis, such as XPS and EDS, proved that the doped lanthanum and europium nano-particles are present only on the TiO2 surface without disturbing the crystal lattice. In the synthesized systems, there were no significant changes in the bandgap energy. Moreover, all the obtained systems were characterized by high thermal stability. One of the key objectives of the work, and a scientific novelty, was the introduction of UV-LED lamps into the metronidazole photo-oxidation pathway. The results of the photo-oxidation study showed that the obtained TiO2 systems doped with selected lanthanides (Eu or La) show high efficiency in the removal of metronidazole, and at the same consuming nearly 10 times less electricity compared to conventional UV lamps (high-pressure mercury lamp). Liquid-chromatography mass-spectrometry (LC-MS) analysis of an intermediate solution showed the presence of fragments of the degraded molecule by m/z 114, 83, and 60, prompting the formulation of a plausible photodegradation pathway for metronidazole.

On the Tribological and Oxidation Study of Xanthophylls as Natural Additives in Castor Oil for Green Lubrication

The present study focuses on an introductory analysis of the use of three xanthophylls as additives for green lubricant applications. For this purpose, the additives were characterized by FTIR and 1H-NMR techniques, and the bio-lubricants were described by their physical properties. The effect of the natural compounds on the friction and wear properties of bio-lubricants were evaluated by sliding friction tests under boundary conditions, as confirmed by an analysis of the lubricating film thickness. The antioxidant capacity was analyzed by FTIR spectroscopy. It was observed better wear protection in castor oil with xanthophylls than without these additives. The wear rate was reduced up to 50% compared with neat oil. Lesser beneficial effects were appreciated in friction coefficient since it was increased 25%. The best contribution was observed with astaxanthin as an additive. In addition, a significant improvement in the oxidation of castor oil, complemented with this additive, was exhibited by FTIR analysis. It was found that xanthophylls could be employed as additives for totally biodegradable lubricant applications since they have better tribological and antioxidant behavior than current additives.

Voltammetric study of formic acid oxidation via active chlorine on IrO2/Ti and RuO2/Ti electrodes

This work aimed to contribute to the mechanism electrochemical oxidation study of organic compounds on DSA electrodes. To do this, IrO₂ and RuO₂ electrodes were prepared thermally at 40°C on Titanium substrate. The prepared electrodes were characterized using voltammetric and SEM techniques. The electrochemical measurements in acid media made it possible to show the presence of IrO₂ and RuO₂ on the surface of the electrode. These electrodes have identical electrocatalytic behaviors both for oxygen evolution and chlorine evolution. The prepared electrodes make it possible to oxidize the organic compounds in an acid media in the absence or in the presence of Cl^-. In acidic electrolytes, water molecules produce hydroxyl radicals that contribute to the higher oxides (RuO₃ or IrO₃) formation. The higher oxides obtained produce O₂ and regenerate the active sites of our electrodes. In the electrolytes containing chlorides, higher oxides fix them (IrO₃(Cl) or RuO₃(Cl)) in competition with the production of O₂. Then IrO₃(Cl) or RuO₃(Cl) reacts with Cl^- to produce Cl₂ and regenerate the adsorbed hydroxyl radicals. The higher oxides also react as a mediator in HCOOH oxidation in competition with O₂ evolvement. In the electrolytes containing HCOOH and Cl^-, the organic pollutant's oxidation occurs indirectly via the hypochlorite ions produced in the solution and on the electrodes. This study showed that the produced OH· and Cl₂ in situ are involved in the oxidation of HCOOH