Current Organic Chemistry - Volume 22, Issue 10, 2018

The Persistent Organic Pollutants (POPs) are compounds (i.e., Polycyclic Aromatic Hydrocarbons PAHs, Polychlorinated Biphenyls PCBs, Polychlorinated dibenzodioxins/ dibenzofurans PCDD/Fs, PBDDs, Polybrominated diphenyl ethers PBDEs, hexachlorocyclohexane isomers HCHs, etc.) with precise physical and chemical properties such that they remain intact for long periods. Because of their persistence, POPs bioaccumulate with potential significant impacts on human health and the environment. Since the last decades, the scientific community has felt the need to investigate such compounds at very low levels and so it has developed novel analytical protocols based on extraction and clean-up procedures followed by Gas Chromatography/High Performance Liquid Chromatography- Mass Spectrometry (GC/HPLC-MS) analysis. This review would like to focus the attention on analytical methodologies set up during the last 5 years (2012-2016): the main papers reporting significant advancements in the analytical protocols for analyzing POPs in different environmental matrices such as air, soil, water and waste, will be illustrated and discussed.

Organochlorine pesticides have been extensively used for eradication of pests in an attempt to increase food security. They are also used for control of vectors that spread infectious diseases. Pest outbreaks and spread of infectious diseases is dominant in tropical countries, such as, India, characterized by high temperature and humidity. This has consequently promoted indiscriminate use of pesticides. Environmental conditions in tropical countries are also conducive for rapid dissipation of toxic pesticide residues from their point of application. Despite the ban on organochlorine pesticides, these are still being used illegally. Due to large-scale production, extensive usage and persistent nature, presence of pesticides is reported throughout the environment, in air, water and soil/sediments. Pesticide residues have also been found both in the Arctic and Antarctic as a result of global distillation. The fate of pesticides is affected by their physicochemical properties, the prevailing environmental conditions and the geographic location. Pesticides may get volatilized into the atmosphere through aerial drift, may enter surface water bodies in dissolved and particulate forms with run-off and may also leach through the soil to contaminate groundwater. Pesticides may get partially transformed through chemical and biological processes. Lipophilic pesticides and their residues have been linked with dramatic population loss in some organisms due to bioaccumulation within tissues and interference in functioning of the endocrine system. This paper attempts to elucidate the fate of organochlorine pesticides in the environment, inherent toxicity and transport and transformation mechanisms that affect their behaviour in the environment.

This manuscript gives a summary of photoinduced processes in several Nitropolycyclic Aromatic Hydrocarbons (NPAHs) (nitronaphthalene, nitrofluorene, nitroanthracene, and nitropyrene) as well as the results of the TD-DFT calculations of the excited states and the geometries in the ground and first singlet excited electronic states of three isomers of nitrophenanthrene (1NPh, 3NPh, and 9NPh) which are presented for the first time. The decay of the first excited singlet state can lead to different pathways depending on a variety of factors: the energy gap between the S1 state and the nearest state from the triplet manifold, geometries of the electronic states, electronic configuration of the states, etc. The gas phase NPAH molecule can bind to particulate matter in the atmosphere and different solvents present in the aerosol can activate or inhibit photoprocesses. These events depend strongly on the solvent polarity. We reviewed experimental studies that explored these variations of photoinduced processes in conjuction with TD-DFT and ab initio computations.

Identification of transformation products and elucidation of degradation pathways of pharmaceuticals in the environment is a challenging task due to the numerous compounds, their low concentrations, and complexity of the environmental matrices. This manuscript summarizes present knowledge about main degradation routes of pharmaceuticals in the environment and review published methods and approaches for their determination in environmental samples, with a special emphasis on the mass spectrometry and nuclear magnetic resonance techniques.

The objective of this study was to summarize the results obtained in a decadelong research project to evaluate novel and conventional technologies (adsorption/bioadsorption, photooxidation, radiolysis, and ozonation) in the treatment of water contaminated with tetracyclines (tetracycline, oxytetracycline, and chlortetracycline). Some of these results have been previously published. It has been found that the adsorption of tetracyclines on activated carbon is governed by dispersive adsorbent-adsorbate interactions and that this process is impeded by the presence of electron deactivating groups in both activated carbons and tetracyclines. The low quantum yield values obtained demonstrate that the application of UV radiation is inefficient to eliminate tetracyclines from water because long exposure times are required to reach 100% of degradation. The application of indirect photolysis, radiolysis and ozonation evidenced that tetracyclines can be effectively degraded from water obtaining the highest degradation rate using ozone and ozone/H2O2. The use of natural water (surface water, groundwater, and wastewater) increased the efficacy of the photodegradation process, with the low concentrations of dissolved organic matter acting as a photosensitizer. However, in general, the effectiveness of advanced oxidation processes was affected by the presence of inorganic anions in the solution, which act as radical scavengers diminishing the amount of radicals in the medium. Finally, the complete mineralization of tetracyclines was not achieved by using these advanced oxidation processes and the byproducts generated in the degradation of oxytetracycline were more toxic in the different types of water. The results obtained in this project have been compared with the most relevant results found in the literature.

The Heck reaction is the most attractive C-C coupling way, which constitutes a universal approach of producing various classes of organic compounds for the development of new processes used in industry. A deeper understanding of the nature of true catalytic species starting with heterogeneous precatalysts will motivate potential breakthroughs in the rational design of future generations of homogeneous C-C coupling catalysts in nature. Heterogeneous catalyst systems are expected to achieve a high turnover number or good catalyst recycling with a minimal level of residual metal in the products via homogeneous catalysis. This review is focused on the investigation of heterogeneity towards Heck reactions with heterogeneous precatalysts, concisely summarizing the worldwide research published up to date with our appropriate discussion. The review includes the literature of heterogeneity studies involving various types of solid material-supported metal particles and various heterogenized metal complexes used as precatalysts. Either the cases where leached metal species from heterogeneous precatalysts were claimed to be true catalysts, or the cases where heterogenized metal species were asserted to contribute to catalysis are presented here. Meanwhile, some important experimentations and methods for assessing catalyst heterogeneity, which are linked with the design of effective homogeneous C-C coupling catalysts using heterogeneous precatalysts are briefly introduced to catalysis readers.