Gold Carbene or Carbenoid: Is There a Difference?

By reviewing the recent progress on the elucidation of the structure of gold carbenes and the definitions of metal carbenes and carbenoids, we recommend to use the term gold carbene to describe gold carbene‐like intermediates, regardless of whether the carbene or carbocation extreme resonance dominates. Gold carbenes, because of the weak metal‐to‐carbene π‐back‐donation and their strongly electrophilic reactivity, could be classified into the broader family of Fischer carbenes, although their behavior and properties are very specific.     

Biomass Valorization Using Natural Deep Eutectic Solvents: What’s New in France?

With the growing interest in more environmentally friendly solvents and processes, the introduction of Natural Deep Eutectic Solvents (NaDES) as low cost, non-toxic and biodegradable solvents represent a new opportunity for green and sustainable chemistry. Thanks to their remarkable advantages, NaDES are now arousing growing interest in many fields of research such as food, health, cosmetics and biofuels. Around the world, NaDES are seen as a promising alternative to commonly used petrochemical solvents. The objective of this review is to draw up a panorama of the existing skills on NaDES in French laboratories and industries for the valuation of natural products. This review therefore focuses on current applications, skills and perspectives, in order to analyze the place of French research in the use of NaDES for the valorization of biomass since 2015.     

Preconcentration and Determination of Chlorophenols in Wastewater with Dispersive Liquid–Liquid Microextraction Using Hydrophobic Deep Eutectic Solvents

Abstract

Hydrophobic deep eutectic solvents (DESs) were synthesized and developed for the preconcentration of three chlorophenols from wastewater by dispersive liquid–liquid microextraction (DLLME). The analyte concentrations were determined by high-performance liquid chromatography (HPLC). The hydrophobic DESs were prepared with the combination of hydrogen bond donors of decanoic acid or octanoic acid with different hydrogen bond acceptors of quaternary ammonium salts of tetrabutylammonium chloride, tetraoctylammonium chloride, methyltrioctylammonium chloride, and tetraheptylammonium chloride). Following the study of the stability and characterization by Fourier transform infrared spectroscopy, the hydrophobic DESs were developed as extractants and employed for the removal of 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) from wastewater. Using hydrophobic DESs as the microextraction solvents, several key parameters were optimized, including the type and volume of the hydrophobic DES, pH, and time of the extraction procedure. Under the optimized conditions, good recoveries from 90.8% to 93.0% were obtained for the three chlorophenols. The limits of detection were less than 0.05?µg/mL with relative standard deviations between 1.8% and 3.1%. The method was applied for the isolation and determination of synthetic chlorophenols in wastewater.     

Acidic Deep Eutectic Solvents as Active Media for Sustainable Synthesis of Biindoles Starting from 2,2’-Diaminotolanes and Aldehydes

We describe an alternative and more sustainable method for the synthesis of 2,2’-disubstituted 3,3’-biindoles starting from 2,2’-diaminotolanes and (hetero)arylaldehydes. The key feature of the approach is the use of an acidic Deep Eutectic Solvent (DES) able to exploit a double activity, i. e., solvent and Brønsted Acid (BA) catalyst, avoiding the use of Volatile Organic Compounds (VOCs) as solvents and additional acid catalysts. By this way, we synthesized twenty-five biindoles, including eighteen new compounds. The reactions run quickly under mild conditions by microwave heating at 70 °C, with yields ranging from good to very good. The reaction scope is rather broad. The medium demonstrated to be reusable at least five times with only a slight reduction in yields. Based on experimental evidence and previous literature findings, a plausible mechanism is proposed.     

Degradable Elastomers: Is There a Future in Tyre Compound Formulation?

Problems related to non-biodegradable waste coming from vulcanized rubber represent one of the pre-eminent challenges for modern society. End-of-life tyres are an important source of this typology of waste and the increasingly high accumulation in the environment has contributed over the years to enhance land and water pollution. Moreover, the release into the environment of non-degradable micro-plastics and other chemicals as an effect of tyre abrasion is not negligible. Many solutions are currently applied to reuse end-of-life tyres as a raw material resource, such as pyrolysis, thermo-mechanical or chemical de-vulcanisation, and finally crumbing trough different technologies. An interesting approach to reduce the environmental impact of vulcanised rubber wastes is represented by the use of degradable thermoplastic elastomers (TPEs) in tyre compounds. In this thematic review, after a reviewing fossil fuel-based TPEs, an overview of the promising use of degradable TPEs in compound formulation for the tyre industry is presented. Specifically, after describing the properties of degradable elastomers that are favourable for tyres application in comparison to used ones, the real scenario and future perspectives related to the use of degradable polymers for new tyre compounds will be realized.     

Charged versus Neutral Hydrogen‐Bonded Complexes: Is There a Difference in the Nature of the Hydrogen Bonds?

A theoretical study on some carboxylic acid dimers formed by positively or negatively charged molecules has been carried out by using DFT methods. The resulting dimers possess either a charge of +2 or ?2. In addition, the corresponding neutral complexes have also been considered. The electron density distribution described by the atoms in molecules and the natural bond orbital methods, as well as the electric field maps of the systems, have been analyzed and compared without finding significant differences between the neutral and ionic complexes. The interaction energy along the dissociation path of the charged dimers shows both a local minimum and a local maximum, defining a stability region between them. When this energetic profile is recalculated by removing the repulsion between the charged groups, it resembles to those of the neutral molecules. Hence, the characteristics of the charged dimers are similar to those of the neutral ones: the addition of a repulsion term for the charged groups permits to retrieve the energetic profiles dependence with the distance in the charged system. The interacting quantum atom (IQA) method has been used to calculate the interaction energy terms, including the classic Coulombic term between the whole molecules and the corresponding of the carboxylic acid groups. The IQA results show repulsive electrostatic interactions when the whole molecules are considered in the ionic complexes, but attractive ones between the carboxylic groups in both neutral and ionic complexes.     

Ultra-Weak Metal−Metal Bonding: Is There a Beryllium-Beryllium Triple Bond?

Metal-metal triple bonds featuring s-block element have not been reported until now. Only Be−Be double bonds between have been predicted theoretically based on the intuitive electron donation from four s¹ type electron-donating ligands. Herein, we theoretically predicted a novel species featuring a Be−Be triple bond in the Li₆Be₂ molecule. The molecule was found to be thermodynamically stable. The presence of the triple bond was confirmed by adaptive natural density partitioning (AdNDP), electron localization function (ELF), and atoms in molecules (AIM) analyses. Moreover, the mechanical strength of the Be−Be triple bond was analyzed by using compliance matrix, pointing towards its ultra-weak nature.     

Is There a Single Ideal Parameter for Halogen-Bonding-Based Lewis Acidity?

Halogen-bond donors (halogen-based Lewis acids) have now found various applications in diverse fields of chemistry. The goal of this study was to identify a parameter obtainable from a single DFT calculation that reliably describes halogen-bonding strength (Lewis acidity). First, several DFT methods were benchmarked against the CCSD(T) CBS binding data of complexes of 17 carbon-based halogen-bond donors with chloride and ammonia as representative Lewis bases, which revealed M05-2X with a partially augmented def2-TZVP(D) basis set as the best model chemistry. The best single parameter to predict halogen-bonding strengths was the static σ-hole depth, but it still provided inaccurate predictions for a series of compounds. Thus, a more reliable parameter, Ω_σ*, has been developed through the linear combination of the σ-hole depth and the σ*(C−I) energy, which was further validated against neutral, cationic, halogen- and nitrogen-based halogen-bond donors with very good performance.     

New Functional Polyolefins: Towards a Bridge Between Catalytic and RAFT Polymerizations?

Summary: Di‐polyethylenyl magnesium compounds, obtained by a transition metal catalyzed chain growth reaction on butyloctyl magnesium, are reacted with a range of disulfides of thiocarbonylated compounds (RC(S)SSC(S)R). Xanthate, dithiocarbamate, dithioester, and trithiocarbonate‐functionalized polyethylenes are thus obtained and characterized by ¹H NMR and IR spectroscopy, and MALDI TOF mass spectrometry. These macroRAFT agents may serve as building blocks for the synthesis of block copolymers based on polyolefins and polar segments.

Thio thiocarbonylate‐terminated polyethylene chains are easily prepared in high yield by a two step reaction and analyzed by MALDI‐TOF mass spectrometry.     

What Difference Does a Methyl Group Make: Pentamethylbenzene?

The crystal structure of pentamethylbenzene has been obtained for the first time with the use of synchrotron radiation, whilst the low‐energy spectrum of lattice dynamics, dominated by the methyl group torsions, was obtained using inelastic neutron scattering. The effect of symmetry lowering by the removal of a single methyl group relative to hexamethylbenzene has been investigated, including the role that this plays in the charge‐transfer characteristics of complexes formed with tetracyanoethylene.     

Air Assisted Dispersive Liquid–Liquid Microextraction (AA-DLLME) Using Hydrophilic–Hydrophobic Deep Eutectic Solvents for the Isolation of Monosaccharides and Amino Acids from Kelp

Abstract

Air assisted dispersive liquid–liquid microextraction (AA-DLLME) using hydrophilic–hydrophobic deep eutectic solvents (DES) was developed for the simultaneous isolation of monosaccharides and amino acids with wide ranges of polarities from kelp using high performance liquid chromatography (HPLC). A response surface methodology (RSM) on a Box–Behnken design (BBD) model was employed to identify the optimal extraction parameters. Air assisted dispersive liquid-phase microextraction performed using the optimum deep eutectic solvent system, five push–pull cycles, a ratio of solid to liquid equal to 3?mg·mL^?1, 10% (w/v) NaCl, and a centrifugation time of 6?min provided the best analytical performance. The optimal extracted concentrations of d-(+)-galactose, l-(-)-fucose, dl-tyrosine, and dl-valine in kelp were 16.7?±?0.2, 8.6?±?0.2, 2.6?±?0.1, and 1.6?±?0.1?mg·g^?1, respectively. The method recoveries for d-(+)-galactose, l-(-)-fucose, dl-tyrosine, and dl-tyrosine were from 87 to 102%, 84 to 103%, 87 to 104%, and 85 to 103%. The relative standard deviations (RSDs) (n?=?4) for the intra-day and inter-day determinations were <6.17%.     

Is There a Novel Biosynthetic Pathway in Mice That Converts Alcohol to Dopamine,Norepinephrine and Epinephrine?

Previous studies in animals and humans have shown multiple types of interaction between alcohol (ethanol) intake and the catecholamine signaling molecules: dopamine, norepinephrine and epinephrine. This literature suggests that the administration of alcohol to rodents affects the central and peripheral (blood plasma) levels of these catecholamines. Two prior publications (Fitzgerald 2012, 2020) put forth the hypothesis that there may be a currently unidentified biosynthetic pathway, in a range of organisms, that actually converts alcohol to dopamine, norepinephrine and epinephrine. This publication describes the details for how to test this hypothesis in mice. Mice can be systemically injected with an intoxicating dose of commercially available stable isotope-labeled ethanol (ethanol-1-¹³C), and blood plasma samples and brains can be collected approximately two to 24 h post-injection. Liquid chromatography-mass spectrometry analysis can then be used to test whether some of the labeled ethanol molecules have been incorporated into new dopamine, norepinephrine, and epinephrine molecules, in plasma and brain samples. If confirmed, this hypothesis may have broadly reaching implications both for basic neuroscience and our understanding of alcohol abuse and alcoholism.     

Is There a “Most Chiral Tetrahedron”?

A degree of chirality is a function that purports to measure the amount of chirality of an object: it is equal for enantiomers, vanishes only for achiral or degenerate objects and is similarity invariant, dimensionless and normalisable to the interval [0,1]. For a tetrahedron of non-zero three-dimensional volume, achirality is synonymous with the presence of a mirror plane containing one edge and bisecting its opposite, and hence it is easy to design degree-of-chirality functions based on edge length that incorporate all constraints. It is shown that such functions can have largest maxima at widely different points in the tetrahedral shape space, and by incorporation of appropriate factors, the maxima can be pushed to any point in the space. Thus the phrase "most chiral tetrahedron" has no general meaning: any chiral tetrahedron is the most chiral for some legitimate choice of degree of chirality.     

Characterization of Supercomplex Crude Oil Mixtures: What Is Really in There?

Through different windows : One major obstacle in energy research is the complexity and variety of compounds present in crude oil. A study of different ionization methods for mass spectrometry shows that the mass spectrum very strongly depends on which method is used.

     

Wine,Polyphenols, and Mediterranean Diets. What Else Is There to Say?

A considerable amount of literature has been published claiming the cardiovascular benefits of moderate (red) wine drinking, which has been considered a distinguishing trait of the Mediterranean diet. Indeed, red wine contains relevant amounts of polyphenols, for which evidence of their biological activity and positive health effects are abundant; however, it is also well-known that alcohol, even at a low level of intake, may have severe consequences for health. Among others, it is directly related to a number of non-communicable diseases, like liver cirrhosis or diverse types of cancer. The IARC classifies alcohol as a Group 1 carcinogen, causally associated with the development of cancers of the upper digestive tract and liver, and, with sufficient evidence, can be positively associated with colorectum and female breast cancer. In these circumstances, it is tricky, if not irresponsible, to spread any message on the benefits of moderate wine drinking, about which no actual consensus exists. It should be further considered that other hallmarks of the Mediterranean diet are the richness in virgin olive oil, fruits, grains, and vegetables, which are also good sources of polyphenols and other phytochemicals, and lack the risks of wine. All of these aspects are reviewed in this article.