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Accounts of Chemical Research Jan 2020The appeal and promise of synthetic organic electrochemistry have been appreciated over the past century. In terms of redox chemistry, which is frequently encountered... (Review)
Review
The appeal and promise of synthetic organic electrochemistry have been appreciated over the past century. In terms of redox chemistry, which is frequently encountered when forging new bonds, it is difficult to conceive of a more economical way to add or remove electrons than electrochemistry. Indeed, many of the largest industrial synthetic chemical processes are achieved in a practical way using electrons as a reagent. Why then, after so many years of the documented benefits of electrochemistry, is it not more widely embraced by mainstream practitioners? Erroneous perceptions that electrochemistry is a "black box" combined with a lack of intuitive and inexpensive standardized equipment likely contributed to this stagnation in interest within the synthetic organic community. This barrier to entry is magnified by the fact that many redox processes can already be accomplished using simple chemical reagents even if they are less atom-economic. Time has proven that sustainability and economics are not strong enough driving forces for the adoption of electrochemical techniques within the broader community. Indeed, like many synthetic organic chemists that have dabbled in this age-old technique, our first foray into this area was not by choice but rather through sheer necessity. The unique reactivity benefits of this old redox-modulating technique must therefore be highlighted and leveraged in order to draw organic chemists into the field. Enabling new bonds to be forged with higher levels of chemo- and regioselectivity will likely accomplish this goal. In doing so, it is envisioned that widespread adoption of electrochemistry will go beyond supplanting unsustainable reagents in mundane redox reactions to the development of exciting reactivity paradigms that enable heretofore unimagined retrosynthetic pathways. Whereas the rigorous physical organic chemical principles of electroorganic synthesis have been reviewed elsewhere, it is often the case that such summaries leave out the pragmatic aspects of designing, optimizing, and scaling up preparative electrochemical reactions. Taken together, the task of setting up an electrochemical reaction, much less inventing a new one, can be vexing for even seasoned organic chemists. This Account therefore features a unique format that focuses on addressing this exact issue within the context of our own studies. The graphically rich presentation style pinpoints basic concepts, typical challenges, and key insights for those "electro-curious" chemists who seek to rapidly explore the power of electrochemistry in their research.
Topics: Electrochemical Techniques; Molecular Structure; Organic Chemicals; Oxidation-Reduction
PubMed: 31823612
DOI: 10.1021/acs.accounts.9b00539 -
Environmental Science and Pollution... May 2022Laboratory testing with spiked sediments with organic contaminants is a valuable tool for ecotoxicologists to study specific processes such as effects of known... (Review)
Review
Laboratory testing with spiked sediments with organic contaminants is a valuable tool for ecotoxicologists to study specific processes such as effects of known concentrations of toxicants, interactions of the toxicants with sediment and biota, and uptake kinetics. Since spiking of the sediment may be performed by using different strategies, a plethora of procedures was proposed in the literature for spiking organic chemicals onto sediments to perform ecotoxicological analyses. In this paper, we reviewed the scientific literature intending to characterise the kind of substrates that were used for spiking (i.e. artificial or field-collected sediment), how the substrates were handled before spiking and amended with the organic chemical, how the spiked sediment was mixed to allow the homogenisation of the chemical on the substrate and finally how long the spiked sediment was allowed to equilibrate before testing. What emerged from this review is that the choice of the test species, the testing procedures and the physicochemical properties of the organic contaminant are the primary driving factors affecting the selection of substrate type, sediment handling procedures, solvent carrier and mixing method. Finally, we provide recommendations concerning storage and characterization of the substrate, equilibrium times and verification of both equilibration and homogeneity.
Topics: Ecotoxicology; Geologic Sediments; Organic Chemicals; Water Pollutants, Chemical
PubMed: 35113376
DOI: 10.1007/s11356-022-18987-5 -
Analytical Chemistry May 2016Chemical attribution signatures (CAS) are being investigated for the sourcing of chemical warfare (CW) agents and their starting materials that may be implicated in...
Chemical attribution signatures (CAS) are being investigated for the sourcing of chemical warfare (CW) agents and their starting materials that may be implicated in chemical attacks or CW proliferation. The work reported here demonstrates for the first time trace impurities from the synthesis of tris(2-chloroethyl)amine (HN3) that point to the reagent and the specific reagent stocks used in the synthesis of this CW agent. Thirty batches of HN3 were synthesized using different combinations of commercial stocks of triethanolamine (TEA), thionyl chloride, chloroform, and acetone. The HN3 batches and reagent stocks were then analyzed for impurities by gas chromatography/mass spectrometry. All the reagent stocks had impurity profiles that differentiated them from one another. This was demonstrated by building classification models with partial least-squares discriminant analysis (PLSDA) and obtaining average stock classification errors of 2.4, 2.8, 2.8, and 11% by cross-validation for chloroform (7 stocks), thionyl chloride (3 stocks), acetone (7 stocks), and TEA (3 stocks), respectively, and 0% for a validation set of chloroform samples. In addition, some reagent impurities indicative of reagent type were found in the HN3 batches that were originally present in the reagent stocks and presumably not altered during synthesis. More intriguing, impurities in HN3 batches that were apparently produced by side reactions of impurities unique to specific TEA and chloroform stocks, and thus indicative of their use, were observed.
Topics: Acetone; Amines; Chemical Warfare Agents; Discriminant Analysis; Ethanolamines; Gas Chromatography-Mass Spectrometry; Least-Squares Analysis; Organic Chemicals; Sulfur Oxides
PubMed: 27116337
DOI: 10.1021/acs.analchem.6b00766 -
Soft Matter Sep 2020Organic chemical gardens of chitosan hydrogel develop upon injecting an acidic chitosan solution into an alkaline solution. Besides complex and budding structures,...
Organic chemical gardens of chitosan hydrogel develop upon injecting an acidic chitosan solution into an alkaline solution. Besides complex and budding structures, tubular hydrogel formations develop that exhibit periodic surface patterns. The underlying wrinkling instability is identified by its characteristic wavelength dependence on the diameter of the elastic material formed. The flow-driven conditions allow precise control over the structure that can help the design of soft bio-inspired materials. Our findings can also suggest a new direction in the field of chemobrionics.
Topics: Chitosan; Hydrogels; Organic Chemicals
PubMed: 32902544
DOI: 10.1039/d0sm01397h -
The Science of the Total Environment Aug 2006Sewage sludges are residues resulting from the treatment of wastewater released from various sources including homes, industries, medical facilities, street runoff and... (Review)
Review
Sewage sludges are residues resulting from the treatment of wastewater released from various sources including homes, industries, medical facilities, street runoff and businesses. Sewage sludges contain nutrients and organic matter that can provide soil benefits and are widely used as soil amendments. They also, however, contain contaminants including metals, pathogens, and organic pollutants. Although current regulations require pathogen reduction and periodic monitoring for some metals prior to land application, there is no requirement to test sewage sludges for the presence of organic chemicals in the U. S. To help fill the gaps in knowledge regarding the presence and concentration of organic chemicals in sewage sludges, the peer-reviewed literature and official governmental reports were examined. Data were found for 516 organic compounds which were grouped into 15 classes. Concentrations were compared to EPA risk-based soil screening limits (SSLs) where available. For 6 of the 15 classes of chemicals identified, there were no SSLs. For the 79 reported chemicals which had SSLs, the maximum reported concentration of 86% exceeded at least one SSL. Eighty-three percent of the 516 chemicals were not on the EPA established list of priority pollutants and 80% were not on the EPA's list of target compounds. Thus analyses targeting these lists will detect only a small fraction of the organic chemicals in sludges. Analysis of the reported data shows that more data has been collected for certain chemical classes such as pesticides, PAHs and PCBs than for others that may pose greater risk such as nitrosamines. The concentration in soil resulting from land application of sludge will be a function of initial concentration in the sludge and soil, the rate of application, management practices and losses. Even for chemicals that degrade readily, if present in high concentrations and applied repeatedly, the soil concentrations may be significantly elevated. The results of this work reinforce the need for a survey of organic chemical contaminants in sewage sludges and for further assessment of the risks they pose.
Topics: Environmental Monitoring; Environmental Pollutants; Organic Chemicals; Sewage
PubMed: 16750559
DOI: 10.1016/j.scitotenv.2006.04.002 -
Current Medicinal Chemistry 2019
Topics: Biomedical Research; Fluorescent Dyes; Organic Chemicals; Spectrometry, Fluorescence
PubMed: 31584359
DOI: 10.2174/092986732621190919104427 -
Environmental Toxicology and Chemistry Feb 2023Efficient monitoring methods must be developed for 1,4-dioxane, which is suspected to be carcinogenic to humans and is highly mobile in aquatic environments. In this...
Efficient monitoring methods must be developed for 1,4-dioxane, which is suspected to be carcinogenic to humans and is highly mobile in aquatic environments. In this regard, polar organic chemical integrative samplers (POCIS) have been utilized extensively as passive samplers for determining time-weighted average concentrations of hydrophilic organic compounds. However, POCIS are difficult to apply to extremely hydrophilic known organic compounds with negative log octanol-water partition coefficient (K ) values due to their limited kinetic sampling time. Using an activated carbon-based sorbent with a high adsorption capacity and a bilayer of silicone and polyethersulfone membranes that inhibit mass transfer to the sorbent, we developed a POCIS device to measure 1,4-dioxane (log K -0.27) in the present study. Permeation and field calibration tests demonstrated that the use of silicone membranes effectively reduces the water-to-sorbent mass transfer rate. The sampling rate and kinetic sampling period determined by field calibration tests were 1.4 ml day and >14 days, respectively. Finally, the developed POCIS device was applied to a landfill treatment plant to determine the 1,4-dioxane concentrations. Environ Toxicol Chem 2023;42:296-302. © 2022 SETAC.
Topics: Humans; Environmental Monitoring; Water Pollutants, Chemical; Organic Chemicals; Water
PubMed: 36349960
DOI: 10.1002/etc.5518 -
Angewandte Chemie (International Ed. in... Dec 2020In this Essay, we present a critical analysis of two common practices in modern chemistry-that is, of using speculations about the "greenness" and "nontoxicity" of... (Review)
Review
In this Essay, we present a critical analysis of two common practices in modern chemistry-that is, of using speculations about the "greenness" and "nontoxicity" of developed synthesis procedures and of a priori labelling various compounds derived from natural sources as being environmentally safe. We note that every organic molecule that contains functional groups should be biologically active. Thus, analysis of the particular greenness and the potential environmental impact of a given chemical process should account for the biological activity of all its components in a measureable (rather than empirical) way. We highlight the necessity of clarifying discussions on biological activity and toxicity and propose possible ways of introducing tox-Profiles as a reliable overview of the overall toxicity of chemical reactions.
Topics: Molecular Structure; Organic Chemicals
PubMed: 33002316
DOI: 10.1002/anie.202003082 -
Chemical Reviews Jun 2016Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular... (Review)
Review
Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.
Topics: Bromine; Organic Chemicals
PubMed: 27199233
DOI: 10.1021/acs.chemrev.5b00400 -
Bioorganic & Medicinal Chemistry Mar 2004
Review
Topics: Electric Conductivity; Ion Channels; Lipid Bilayers; Membrane Proteins; Models, Chemical; Models, Molecular; Organic Chemicals; Peptide Fragments; Protein Conformation
PubMed: 15018901
DOI: 10.1016/j.bmc.2003.08.036