Green Chemical Synthesis Research Articles

Photobiocatalysis: Activating Redox Enzymes by Direct or Indirect Transfer of Photoinduced Electrons.

Biocatalytic transformation has received increasing attention in the green synthesis of chemicals because of the diversity of enzymes, their high catalytic activities and specificities, and mild reaction conditions. The idea of solar energy utilization in chemical synthesis through the combination of photocatalysis and biocatalysis provides an opportunity to make the "green" process greener. Oxidoreductases catalyze redox transformation of substrates by exchanging electrons at the enzyme's active site, often with the aid of electron mediator(s) as a counterpart. Recent progress indicates that photoinduced electron transfer using organic (or inorganic) photosensitizers can activate a wide spectrum of redox enzymes to catalyze fuel-forming reactions (e.g., H2 evolution, CO2 reduction) and synthetically useful reductions (e.g., asymmetric reduction, oxygenation, hydroxylation, epoxidation, Baeyer-Villiger oxidation). This Review provides an overview of recent advances in light-driven activation of redox enzymes through direct or indirect transfer of photoinduced electrons.

Mechanochemical Post-Polymerization Modification: Solvent-Free Solid-State Synthesis of Functional Polymers.

Mechanochemical postpolymerization modification is reported herein. The fast and efficient synthesis of a library of macromolecules with functional diversity and structural uniformity was realized without a solvent by means of a high speed ball-milling technique. A series of polymers prepared from 4-vinylbenzaldehyde (4-VBA) underwent solid-state Schiff base formations with a series of amines and amine derivatives. The efficient mixing and energy delivery provided by the collisions between balls not only promoted rapid imine formation but also eliminated the need for a chemical solvent, which is highly desirable for green chemical synthesis.

Literally Green Chemical Synthesis of Artemisinin from Plant Extracts.

Active pharmaceutical ingredients are either extracted from biological sources-where they are synthesized in complex, dynamic environments-or prepared in stepwise chemical syntheses by reacting pure reagents and catalysts under controlled conditions. A combination of these two approaches, where plant extracts containing reagents and catalysts are utilized in intensified chemical syntheses, creates expedient and sustainable processes. We illustrate this principle by reacting crude plant extract, oxygen, acid, and light to produce artemisinin, a key active pharmaceutical ingredient of the most powerful antimalarial drugs. The traditionally discarded extract of Artemisia annua plants contains dihydroartemisinic acid-the final biosynthetic precursor-as well as chlorophyll, which acts as a photosensitizer. Efficient irradiation with visible light in a continuous-flow setup produces artemisinin in high yield, and the artificial biosynthetic process outperforms syntheses with pure reagents.

In vivo antimicrobial activity of silver nanoparticles produced via a green chemistry synthesis using Acacia rigidula as a reducing and capping agent.

IntroductionOne of the main issues in the medical field and clinical practice is the development of novel and effective treatments against infections caused by antibiotic-resistant bacteria. One avenue that has been approached to develop effective antimicrobials is the use of silver nanoparticles (Ag-NPs), since they have been found to exhibit an efficient and wide spectrum of antimicrobial properties. Among the main drawbacks of using Ag-NPs are their potential cytotoxicity against eukaryotic cells and the latent environmental toxicity of their synthesis methods. Therefore, diverse green synthesis methods, which involve the use of environmentally friendly plant extracts as reductive and capping agents, have become attractive to synthesize Ag-NPs that exhibit antimicrobial effects against resistant bacteria at concentrations below toxicity thresholds for eukaryotic cells.PurposeIn this study, we report a green one-pot synthesis method that uses Acacia rigidula extract as a reducing and capping agent, to produce Ag-NPs with applications as therapeutic agents to treat infections in vivo.Materials and methodsThe Ag-NPs were characterized using transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, energy-dispersive spectroscopy, ultraviolet–visible, and Fourier transform infrared.ResultsWe show that Ag-NPs are spherical with a narrow size distribution. The Ag-NPs show antimicrobial activities in vitro against Gram-negative (Escherichia coli, Pseudomonas aeruginosa, and a clinical multidrug-resistant strain of P. aeruginosa) and Gram-positive (Bacillus subtilis) bacteria. Moreover, antimicrobial effects of the Ag-NPs, against a resistant P. aeruginosa clinical strain, were tested in a murine skin infection model. The results demonstrate that the Ag-NPs reported in this work are capable of eradicating pathogenic resistant bacteria in an infection in vivo. In addition, skin, liver, and kidney damage profiles were monitored in the murine infection model, and the results demonstrate that Ag-NPs can be used safely as therapeutic agents in animal models.ConclusionTogether, these results suggest the potential use of Ag-NPs, synthesized by green chemistry methods, as therapeutic agents against infections caused by resistant and nonresistant strains.

Multilayer Graphene Oxide-Silver Nanoparticle Nanostructure as Efficient Peroxidase Mimic

In this work, platinum (Pt), titanium (Ti) and silver (Ag) doped graphene oxide (GO) nanostructures were synthesized by using sonochemical technique, a relatively new technique in nanomaterial synthesis, and characterized in detail. The synthesized nanomaterials were characterized utulizing transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). TEM images and XPS spectras showed that the dopping process was successful. In addition, a multilayer graphene oxide-silver nanoparticles (M-GO-AgNPs) nano-structure was synthesized in this study for the first time, and it’s electrochemical performance was compared with GO-AgNPs. As a result of electrochemical studies, the rate constants of the GO-AgNPs and M-GO-AgNPs modified electrodes were found as ksanodic= 6.62 s-1 and ksanodic= 6.78 s-1, respectively. Finally, the M-GO-AgNPs nano-structure obtained by sonochemical technique, a green chemistry synthesis technique, has been found to be suitable for use as an electrochemical sensor matrix.

Revealing the Structure and Mechanism of Palladium during Direct Synthesis of Hydrogen Peroxide in Continuous Flow Using Operando Spectroscopy

The direct synthesis of H2O2 is a dream reaction in the field of selective oxidation and green chemical synthesis. However, the unknown active state of the catalyst and the lack of a defined catalytic mechanism preclude the design and optimization of suitable catalysts and reactor setups. Here direct synthesis of H2O2 over Pd–TiO2 in water was investigated in a continuous flow reactor setup utilizing undiluted oxygen and hydrogen to increase aqueous-phase concentrations safely at ambient temperature and a pressure of 10 bar. In this experiment operando X-ray absorption spectroscopy (XAS) and online flow injection analysis for photometric quantification of H2O2 were combined to build catalyst structure–activity relationships in direct H2O2 synthesis. XAS at the Pd K absorption edge was used to observe the oxidation state and local Pd structure together with H2O2 production for three reactant ratio (H2/O2) regimes: hydrogen rich (>2), hydrogen lean (<0.5), and balanced (0.5–2). During H2O2 production, oxyge...

1-Dimensional Selective Nuclear Overhauser Effect NMR Spectroscopy To Characterize Products from a Two-Step Green Chemistry Synthesis

One dimensional (1-D) 1H and 13C NMR experiments are common tools used in undergraduate organic laboratories to characterize synthesized molecules. However, 1-D NMR spectra cannot always provide un...

A Novel Dihydropyridines C-Glycosylated Compound by Hantzsch Cyclo-Condensation

The Hantzsch synthesis has been used for the preparation of the 1,4-Dihydropyridines compounds with different pharmacophore groups. The use of a designed glycosylated compound in Hantzsch synthesis would lead to a novel Dihydropyridines C-Glycosylated compound. We used the 6-methoxy-2, 2-dimethyltetrahydrofuro [3, 4-d] [1, 3] dioxole-4-carbaldehyde as a glycosylated-based aldehydes. The 4-(3,4-Dihydroxy-5-methoxy-tetrahydro-furan-2-yl)-2,6-dimethyl-1,4-dihydro-pyridine-3,5-dicarboxy-lic acid 3-ethyl ester 5-methyl ester was synthesized. The structure of compounds was determined by NMR spectroscopy, FTIR and mass spectroscopy methods. We synthesized this 1,4-Dihydropyridines compound by ionic liquid under ultrasound irradiation as a green chemistry synthesis.

Synthetic Gene Regulation in Cyanobacteria.

Cyanobacteria are appealing hosts for green chemical synthesis due to their use of light and carbon dioxide. To optimize product yields and titers, specific and tunable regulation of the metabolic pathways is needed. Synthetic biology has increased and diversified the genetic tools available for biological process control. While early tool development focused on commonly used heterotrophs, there has been a recent expansion of tools for cyanobacteria. CRISPR-Cas9 has been used to edit the genome of cyanobacterial strains, while transcriptional regulation has been accomplished with CRISPR interference and RNA riboswitches. Promoter development has produced a significant number of transcriptional regulators, including those that respond to chemicals, environmental signals, and metabolic states. Trans-acting RNAs have been utilized for posttranscriptional and translational control. The regulation of translation initiation is beginning to be explored with ribosome binding sites and riboswitches, while protein degradation tags have been used to control expression levels. Devices built from multiple parts have also been developed to create more complex behaviors. These advances in development of synthetic cyanobacterial regulatory parts provide the groundwork for creation of new, even more sophisticated bioprocess control devices, bolstering the viability of cyanobacteria as sustainable biotechnology platforms.

Luminescent Silicon Nanocrystal embedded Sodium Silicate Glass

Green luminescent silicon nanoparticles (Si NPs), embedded in sodium silicate (SS) based glass, have been prepared by a simple green chemical synthesis route. (3-aminopropyl) triethoxysilane (APTES) was reduced by sodium ascorbate (SA) in a one-step synthesis method to prepare Si NPs. Extending the same route SS based glass was synthesised by slow evaporation of the aqueous solution of colloidal Si NPs at room temperature. Colloids of Si NPs and the SS-based glass exhibit intense room temperature greenish photoluminescence (PL) that can be detected with the naked eye. Structural investigations reveal that the Si NP sample contains dominant amorphous phase with trace amount of Si nanocrystals (NCs). Analysis of optical properties of the Si NP sample indicates that green PL is dominantly due to the contribution of oxide enriched surface states rather than quantum confinement of excitons and likewise the PL from the SS based glass is due to the presence of trace amount of Si NCs along with agglomerated amorphous oxide embedded in the glass. There is a clear indication of selective reflectance from the prepared SS based glass.

Plasma-Triggered CH4/NH3 Coupling Reaction for Direct Synthesis of Liquid Nitrogen-Containing Organic Chemicals.

Nitrogen-containing organic chemicals such as amines, amides, nitriles, and hydrazones are crucial in chemical and medical industries. This paper reports a direct synthesis of N,N-dimethyl cyanamide [(CH3)2NCN] and amino acetonitrile (NH2CH2CN) through a methane/ammonia (CH4/NH3) coupling reaction triggered by dielectric barrier discharge plasma, with by-products of hydrazine, amines, and hydrazones. The influence of CH4/NH3 molar ratio, feedstock residence time, and specific energy input on the CH4/NH3 plasma coupling reaction has been investigated and discussed. Under the optimized conditions, the productivities of (CH3)2NCN and NH2CH2CN reached 0.46 and 0.82 g·L–1·h–1, respectively, with 8.83% CH4 conversion. In addition, through combining the optical emission spectra diagnosis and the reaction results, a possible CH4/NH3 plasma coupling reaction mechanism has been proposed. This paper provides a potential fine application of CH4 and NH3 in green synthesis of liquid nitrogen-containing organic chemicals, such as nitriles, amines, amides, and hydrazones.

Chemically functionalized activated carbon with 8-hydroxyquinoline using aryldiazonium salts/diazotization route: Green chemistry synthesis for oxins-carbon chelators

The past few years witnessed the emergence of aryldiazonium salts as versatile coupling agents for the functionalization of carbon and other substrates. Although the approach has demonstrated extensive applications in many fields, its use for the synthesis of chelating resins has not been explored. In this work, the concept has been exploited to develop an ecofriendly synthetic method for carbon based chelators. Herein, the p-nitroanline aryldiazonium salt was generated (in situ) in presence of hypophosphorous acid and covalently grafted onto activated carbon (AC) to allow addition of 8-hydroxyquinoline (8-HQ) via diazo coupling. The successfulness of the functionalization was confirmed by DRIR, XPS, and TGA. The risen was packed into cartridges and used with standard solid phase extraction (SPE) apparatus for the extraction of trace metals; Cd(II), Ni(II), Mn(II), Zn(II) and Pb(II) from groundwater samples prior to their measurement by ICPMS. The resin exhibited more 50% enhancement in capacity exchange relative to the plain AC. Under the optimum conditions the sorption capacity of the sorbent was 0.393, 0.170, 0.345, 0.092, 0.314 mmol g−1 for Mn(II), Cd(II), Ni(II), Pb(II) and Zn(II) respectively. The sorbent showed efficient performance when applied for SPE of trace metals from groundwater certified reference materials BCR-609 and groundwater real samples from AlMadinah AlMumnawarah, Saudi Arabia.

Supported Single-Site Ti(IV) on a Metal–Organic Framework for the Hydroboration of Carbonyl Compounds

A stable and structurally well-defined titanium alkoxide catalyst supported on a metal–organic-framework (MOF) of UiO-67 topology (ANL1-Ti(OiPr)2) was synthesized and fully characterized by a variety of analytical and spectroscopic techniques, including BET, TGA, PXRD, XAS, DRIFT, SEM, and DFT computations. The Ti-functionalized MOF was demonstrated active for the catalytic hydroboration of a wide range of aldehydes and ketones with HBpin as the boron source. Compared to traditional homogeneous and supported hydroboration catalysts, ANL1-Ti(OiPr)2 is completely recyclable and reusable, making it a promising hydroboration catalyst alternative for green and sustainable chemical synthesis. In addition, ANL1-Ti(OiPr)2 catalyst exhibits remarkable hydroboration selectivity toward aldehydes vs ketone in competitive study. DFT calculations suggest that the catalytic hydroboration proceeds via a (1) hydride transfer between the active Ti-hydride species and a carbonyl moiety (rate-determining step) and (2) alkoxi...

Transesterification Synthesis of Chloramphenicol Esters with the Lipase from Bacillus amyloliquefaciens.

This work presents a synthetic route to produce chloramphenicol esters by taking advantage the high enantio- and regio-selectivity of lipases. A series of chloramphenicol esters were synthesized using chloramphenicol, acyl donors of different carbon chain length and lipase LipBA (lipase cloned from Bacillus amyloliquefaciens). Among acyl donors with different carbon chain lengths, vinyl propionate was found to be the best. The influences of different organic solvents, reaction temperature, reaction time, enzyme loading and water content on the synthesis of the chloramphenicol esters were studied. The synthesis of chloramphenicol propionate (0.25 M) with 4.0 g L−1 of LipBA loading gave a conversion of ~98% and a purity of ~99% within 8 h at 50 °C in 1,4-dioxane as solvent. The optimum mole ratio of vinyl propionate to chloramphenicol was increased to 5:1. This is the first report of B. amyloliquefaciens lipase being used in chloramphenicol ester synthesis and a detailed study of the synthesis of chloramphenicol propionate using this reaction. The high enzyme activity and selectivity make lipase LipBA an attractive catalyst for green chemical synthesis of molecules with complex structures.

Students attend summer school on green chemistry

The 2017 ACS Summer School on Green Chemistry & Sustainable Energy took place at the Colorado School of Mines on June 20–27. The annual program, supported and financed by ACS, the ACS Green Chemistry Institute, and the ACS Petroleum Research Fund, is open to graduate students and postdoctoral scholars from institutions in the Americas. This year’s class of 53 students represented institutions in Argentina, Brazil, Canada, Colombia, Mexico, the U.S., and Uruguay. The schedule began with a barbecue and concluded with a banquet. Instructors from institutions in Canada and the U.S. gave presentations on the principles and practice of green chemistry, including information on biomass, fossil fuels, fuel cells, green chemistry education, ionic liquids, nanotechnology, research, solvents, synthesis, and toxicology. Additionally, instructors gave presentations on careers, entrepreneurship, research grant proposal writing, and ACS resources for graduate students and postdoctoral scholars. Students learned about ea...

Colorimetric Detection of Mercury(II) Ion in Aqueous Solution Using Silver Nanoparticles.

Novel green-chemistry synthesis of silver nanoparticles (AgNPs) is introduced as a low-cost, rapid and easy-to-use analytical method for mercury ion detection. Aqueous fruit extract of water apple (Syzygium aqueum) was used for the first time as bioreductant to synthesize stable AgNPs. The prepared AgNPs have a yellowish-brown color with a surface plasmon resonance peak at 420 nm. The addition of Hg(II) ions then changes the AgNPs color to colorless. The color change was in proportion to the concentration of Hg(II) ions. The presence of other metal ions in the system was also evaluated. The proposed method shows good selectivity and sensitivity towards Hg(II) ions. Using UV-visible spectrophotometry, the detection limit of the developed method was 8.5 × 10-7 M. The proposed method has been successfully applied for determination of Hg(II) ions in tap and lake water samples with precision better than 5%.

Green solid-state chemical synthesis and excellent xylene-detecting behaviors of Y-doped α-MoO3 nanoarrays

Y-doped α-MoO3 nanoarrays constructed by nanorods were simply synthesized by a facile and simple two-step solid-state chemical reaction. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy were applied to characterize the micro-structures and surface chemical composition of the as-prepared products. The results suggested that Y element had been successfully doped into the α-MoO3 nanoarrays. The gas-sensing behaviors of Y-doped nanoarrays toward seven kinds of harmful gases were also investigated. The results indicated that the Y-doped α-MoO3 nanoarrays display not only an improved response (the response value reaches 28.3 to 100ppm xylene), but also an excellent selectivity to xylene. The good xylene-detecting behaviors were attributed to smaller size and the relative larger surface area. Furthermore, the doping of Y increased the electron donor defects and oxygen vacancies, which accelerated the mobility of oxygen ions and enhanced the conductivity of material, resulting in enhanced response to xylene.

The effect of A-site element on CO2 resistance of O2-selective La-based perovskite hollow fibers

Abstract Oxygen-selective mixed ionic-electronic conducting (MIEC) ceramic membrane technology enables clean coal combustion and membrane reactor for green chemical synthesis. To be practical in these applications that involve CO 2 presence, the membrane materials should have simultaneously high CO 2 resistance and oxygen permeation fluxes. This work probed these properties for the perovskite oxide family of La 0.6 X 0.4 FeO 3-δ (X = Mg, Ca, Sr, or Ba), i.e., La 0.6 Mg 0.4 FeO 3-δ (LMF), La 0.6 Ca 0.4 FeO 3-δ (LCF), La 0.6 Sr 0.4 FeO 3-δ (LSF), and La 0.6 Ba 0.4 FeO 3-δ (LBF) in the hollow fiber membrane geometry that is highly suitable for industrial application. LCF hollow fiber displayed the best balance in CO 2 resistance and oxygen permeation fluxes.

Recent advances in visible-light-driven organic reactions

Abstract In recent years, visible-light-driven organic reactions have been experiencing a significant renaissance in response to topical interest in environmentally friendly green chemical synthesis. The transformations using inexpensive, readily available visible-light sources have come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In this review, we focus on recent advances in the development of visible-light-driven organic reactions, including aerobic oxidation, hydrogen-evolution reactions, energy-transfer reactions and asymmetric reactions. These key research topics represent a promising strategy towards the development of practical, scalable industrial processes with great environmental benefits.

Surfactant‐Free Shape Control of Gold Nanoparticles Enabled by Unified Theoretical Framework of Nanocrystal Synthesis

Gold nanoparticles have unique properties that are highly dependent on their shape and size. Synthetic methods that enable precise control over nanoparticle morphology currently require shape-directing agents such as surfactants or polymers that force growth in a particular direction by adsorbing to specific crystal facets. These auxiliary reagents passivate the nanoparticles' surface, and thus decrease their performance in applications like catalysis and surface-enhanced Raman scattering. Here, a surfactant- and polymer-free approach to achieving high-performance gold nanoparticles is reported. A theoretical framework to elucidate the growth mechanism of nanoparticles in surfactant-free media is developed and it is applied to identify strategies for shape-controlled syntheses. Using the results of the analyses, a simple, green-chemistry synthesis of the four most commonly used morphologies: nanostars, nanospheres, nanorods, and nanoplates is designed. The nanoparticles synthesized by this method outperform analogous particles with surfactant and polymer coatings in both catalysis and surface-enhanced Raman scattering.