Real-Time Monitoring of the Atrazine Degradation by Liquid Chromatography and High-Resolution Mass Spectrometry: Effect of Fenton Process and Ultrasound Treatment.

High resolution mass spectrometry (HRMS) was coupled with ultra-high-performance liquid chromatography (uHPLC) to monitor atrazine (ATZ) degradation process of Fenton/ultrasound (US) treatment in real time. Samples were automatically taken through a peristaltic pump, and then analysed by HPLC-HRMS. The injection in the mass spectrometer was performed every 4 min for 2 h. ATZ and its degradation metabolites were sampled and identified. Online Fenton experiments in different equivalents of Fenton reagents, online US experiments with/without Fe2+ and offline Fenton experiments were conducted. Higher equivalents of Fenton reagents promoted the degradation rate of ATZ and the generation of the late-products such as Ammeline (AM). Besides, adding Fe2+ accelerated ATZ degradation in US treatment. In offline Fenton, the degradation rate of ATZ was higher than that of online Fenton, suggesting the offline samples were still reacting in the vial. The online analysis precisely controls the effect of reagents over time through automatic sampling and rapid detection, which greatly improves the measurement accuracy. The experimental set up proposed here both prevents the degradation of potentially unstable metabolites and provides a good way to track each metabolite.

Degradation of Residual Herbicide Atrazine in Agri-Food and Washing Water.

Atrazine, an herbicide used to control grassy and broadleaf weed, has become an essential part of agricultural crop protection tools. It is widely sprayed on corn, sorghum and sugar cane, with the attendant problems of its residues in agri-food and washing water. If ingested into humans, this residual atrazine can cause reproductive harm, developmental toxicity and carcinogenicity. It is therefore important to find clean and economical degradation processes for atrazine. In recent years, many physical, chemical and biological methods have been proposed to remove atrazine from the aquatic environment. This review introduces the research works of atrazine degradation in aqueous solutions by method classification. These methods are then compared by their advantages, disadvantages, and different degradation pathways of atrazine. Moreover, the existing toxicological experimental data for atrazine and its metabolites are summarized. Finally, the review concludes with directions for future research and major challenges to be addressed.

Electrocatalytic Oxidative Transformation of Organic Acids for Carbon-Heteroatom and Sulfur-Heteroatom Bond Formation.

The electrolysis of organic acids has garnered increasing attention in recent years. In addition to the famous electrochemical decarboxylation known as Kolbe electrolysis, a number of other electrochemical processes have been recently established that allow for the construction of carbon-heteroatom and sulfur-heteroatom bonds from organic acids. Herein, recent advances in electrochemical C-X and S-X (X=N, O, S, Se) bond-forming reactions from five classes of organic acids and their conjugate bases, namely, carboxylic, thiocarboxylic, phosphonic, sulfinic, and sulfonic acids, are surveyed.

Transition-Metal-Free Borylation of Alkyl Iodides via a Radical Mechanism.

We describe an operationally simple transition-metal-free borylation of alkyl iodides. This method uses commercially available diboron reagents as the boron source and exhibits excellent functional group compatibility. Furthermore, a diverse range of primary and secondary alkyl iodides could be effectively transformed to the corresponding alkylboronates in excellent yield. Mechanistic investigations suggest that this borylation reaction proceeds through a single-electron transfer mechanism featuring the generation of an alkyl radical intermediate.

C-H Bond Carboxylation with Carbon Dioxide.

Carbon dioxide is a nontoxic, renewable, and abundant C1 source, whereas C-H bond functionalization represents one of the most important approaches to the construction of carbon-carbon bonds and carbon-heteroatom bonds in an atom- and step-economical manner. Combining the chemical transformation of CO2 with C-H bond functionalization is of great importance in the synthesis of carboxylic acids and their derivatives. The contents of this Review are organized according to the type of C-H bond involved in carboxylation. The primary types of C-H bonds are as follows: C(sp)-H bonds of terminal alkynes, C(sp2 )-H bonds of (hetero)arenes, vinylic C(sp2 )-H bonds, the ipso-C(sp2 )-H bonds of the diazo group, aldehyde C(sp2 )-H bonds, α-C(sp3 )-H bonds of the carbonyl group, γ-C(sp3 )-H bonds of the carbonyl group, C(sp3 )-H bonds adjacent to nitrogen atoms, C(sp3 )-H bonds of o-alkyl phenyl ketones, allylic C(sp3 )-H bonds, C(sp3 )-H bonds of methane, and C(sp3 )-H bonds of halogenated aliphatic hydrocarbons. In addition, multicomponent reactions, tandem reactions, and key theoretical studies related to the carboxylation of C-H bonds are briefly summarized. Transition-metal-free, organocatalytic, electrochemical, and light-driven methods are highlighted.

Oxidant-Free C(sp2)-H Functionalization/C-O Bond Formation: A Kolbe Oxidative Cyclization Process.

An anodic oxidation/cyclization of 2-arylbenzoic acids for the synthesis of dibenzopyranones has been developed. The reaction proceeds at room temperature with no oxidant or electrolyte required and exhibits a high atom economy with H2 being the only byproduct. A series of dibenzopyranones was obtained in good to excellent yields. Urolithins A, B, and C are formally synthesized by adopting this method as a key step to demonstrate its synthetic utility.