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.

Charge Utilization Efficiency and Side Reactions in the Electrochemical Mechanical Polishing of 4H-SiC (0001)

Slurryless electrochemical mechanical polishing (ECMP) is very effective in the polishing of silicon carbide (SiC) wafers. To achieve a high material removal rate (MRR) of SiC wafer using ECMP with low electrical energy loss, charge utilization efficiency in the anodic oxidation of the SiC surface was investigated and the underlying mechanism was clarified by modeling the anodic oxidation system of SiC in 1 wt% NaCl aqueous solution. The charge utilization efficiency in the anodic oxidation of SiC was found to be constant when the current density was less than 20 mA/cm2 and significantly decreased when the current density was greater than 30 mA/cm2, resulting in a significant reduction in the MRR. Modeling of the anodic oxidation system indicates that the charge utilization efficiency depended on the potential applied on the SiC surface: the oxidation of SiC occupied the dominant position in the anodizing system when the potential is lower than 25 V vs Ag|AgCl, charge utilization efficiency greatly decreased when the applied potential was greater than 25 V owing to the occurrence of oxidations of the H2O and Cl-. This research provides both a theoretical and practical foundation for using ECMP to polish SiC wafers.

COD, TOC determination using UV spectrophotometry and its application to monitor the potassium hydrogen phthalate degradation by H2O2-HCO3– oxidation system

In this study, the COD and TOC in H2O2-HCO3– oxidation system containing potassium hydrogen phthalate were determined by UV spectrophotometry (260-310 nm). The pH and H2O2 concentrations were investigated as factors influencing the absorbance measurements. The obtained standard curves were Abs = (3.10±0.04)x103xCOD - (0.015±0.003) (R2=0.9996) with LOD of 5.1 mg O2/l and LOQ of 13.6 mg O2/l, and Abs = (0.008±0.0001)xTOC - (0.015±0.003) (R2=0.9996) with LOD of 1.6 mg/l and LOQ of 5.4 mg/l. The method was applied to monitor the degradation of potassium hydrogen phthalate by the H2O2-HCO3– oxidation system. The results revealed that the COD and TOC removal efficiencies reached ~85% after 90 minutes of UVC irradiation. The UV spectra and HPLC chromatographs showed that no aromatic compounds were obtained in the degradation products.

Cleavage via Selective Catalytic Oxidation of Lignin or Lignin Model Compounds into Functional Chemicals

Lignin, a complex aromatic polymer with different types of methoxylated phenylpropanoid connections, enables the sustainable supply of value-added chemicals and biofuels through its use as a feedstock. Despite the development of numerous methodologies that upgrade lignin to high-value chemicals such as drugs and organic synthesis intermediates, the variety of valuable products obtained from lignin is still very limited, mainly delivering hydrocarbons and oxygenates. Using selective oxidation and activation cleavage of lignin, we can obtain value-added aromatics, including phenols, aldehydes, ketones, and carboxylic acid. However, biorefineries will demand a broad spectrum of fine chemicals in the future, not just simple chemicals like aldehydes and ketones containing simple C = O groups. In particular, most n-containing aromatics, which have found important applications in materials science, agro-chemistry, and medicinal chemistry, such as amide, aniline, and nitrogen heterocyclic compounds, are obtained through n-containing reagents mediating the oxidation cleavage in lignin. This tutorial review provides updates on recent advances in different classes of chemicals from the catalytic oxidation system in lignin depolymerization, which also introduces those functionalized products through a conventional synthesis method. A comparison with traditional synthetic strategies reveals the feasibility of the lignin model and real lignin utilization. Promising applications of functionalized compounds in synthetic transformation, drugs, dyes, and textiles are also discussed.

Fenton and Fenton-like wet oxidation for degradation and destruction of organic radioactive wastes

Fenton or Fenton-like oxidation for treatment of organic radioactive wastes is a promising technology with applications to a range of organic wastes. This review details this process; exploring potential challenges, pitfalls and opportunities for industrial usage with radioactive wastes. The application of this process to real radioactive wastes within pilot-plant settings has been documented, with key findings critically assessed in the context of future waste production. Although this oxidation process has not found mainstream success in treatment of radioactive wastes, a lower temperature oxidation system bring certain benefits, specifically for higher volume or problematic organic wastestreams.