Amide Anion Research Articles

Rotational Behavior Analysis of Cluster Anions in Solid-State Electrolytes via MD Simulation

Solid-state batteries (SSBs) have the potential to bring about dramatic increases in safety and performance compared to current liquid electrolyte systems, allowing for electrification of crucial sectors such as transportation as well as development of novel device architectures for consumer electronics. Finding a suitable solid-state electrolyte remains a key challenge in the path to realization of SSBs, and finding candidate materials that exhibit sufficient ionic conductivity alongside the many other materials properties required of a solid-state electrolyte is the crux of this challenge. Within the past two decades, historic improvements in the conductivities of solid-state electrolytes have been made by understanding and exploiting the effects of lattice volume, vacancy concentration, and concerted migration mechanisms (amongst others), to the point at which the conductivities of some solid-state electrolytes have surpassed those of commercially used liquid electrolytes.[1] Recently, the influence of the dynamics of the anions, specifically the rotation of “cluster anions” (also known as molecular anions or polyanions such as PS4 3- or BH4 -), on cation migration mechanisms has garnered attention as a potential avenue for designing high conductivity materials.[2] Typical experimental signatures of cluster anion rotation include rotor atom spatial probability density calculated from diffraction techniques showing a different, more spherically symmetric geometry, such as a tetrahedral anion showing an octahedral signal, or a disorder-increasing phase transformation accompanied by a sharp jump in ionic conductivity. Because the cluster anion rotations occur at picosecond and Angstrom time and length scales, understanding the rotational behavior of the cluster anions and determining whether this behavior has an impact on the migration mechanism anion is difficult to do experimentally. Molecular dynamics simulations have been used to probe the rotational behavior of cluster anions, with typical characterizations including vibration/libration spectra, rotational autocorrelation functions, spatial probability densities of rotor atoms, and 2D histograms of θ-ϕ spherical coordinates of rotor bond vectors. However, most of these techniques average the signals from the rotor atoms across clusters and across simulation times in a way that obfuscates important time dependent behavior (see Figure 1A). For example, they are unable to determine the specific set of orientations accessed by a cluster anion species that creates the time and space averaged signal seen by diffraction techniques.In this work, we present a novel framework for MD trajectory analysis which uses a 3D parameterization of the orientation of each cluster in each frame to (1) determine the stable orientations (an orientation-based analog of the position-based concept of a lattice site) of a rotationally active cluster anion, (2) characterize the rotations between stable orientations, and (3) probe the interaction between cluster anion rotations and cation migrations. We apply this framework to the dual cluster anion containing electrolyte sodium amide borohydride (Na2NH2BH4), for which both the tetrahedral borohydride (BH4 -) anion and the bent amide (NH2 -) anion show octahedral signals by X-ray and neutron diffraction. We determine that the borohydride anions achieve this averaged spatial density by pointing one hydrogen atom along the +/- a, b, or c axis and rotating about that axis, while the amide anions achieve this by pointing both hydrogen atoms roughly along two adjacent +/- a, b, or c axes (see Figure 1B). We also corroborate previous results showing that the migration of the sodium cations happens in close concert with the rotation of the amide anions, while the borohydride anions spin more freely.This work was supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

Physicochemical and Thermal Behaviors of Room-Temperature Phosphonium Ionic Liquids Based on Fluorosulfonyl(trifluoromethylsulfonyl)Amide Anion As Potential Electrolytes

The physicochemical properties of novel room-temperature ionic liquids based on quaternary phosphonium cations in combination with asymmetric fluorosulfonyl(trifluoromethylsulfonyl)amide anion were reported. It was found that such phosphonium ionic liquids showed lower melting points than those of the conventional amide anion-based ionic liquids. Typical density and transport property behaviors for ionic liquids were observed. Several phosphonium ionic liquids based on fluorosulfonyl(trifluoromethylsulfonyl)amide anion exhibited low viscosities. The phosphonium ionic liquids based on fluorosulfonyl(trifluoromethylsulfonyl)amide anion exhibited relatively low thermal stability when compared to the corresponding conventional amide anion-based ionic liquids.

Effect of Ionic Liquids with Different Structures on Rheological Properties of Water-Based Drilling Fluids and Mechanism Research at Ultra-High Temperatures.

The rheology control of water-based drilling fluids at ultra-high temperatures has been one of the major challenges in deep or ultra-deep resource exploration. In this paper, the effects of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonimide) (ILA), 1-ethyl-3-methylimidazolium tetrafluoroborate (ILB) and N-methyl, butylpyrrolidinium bis(trifluoromethanesulfonimide) (ILC) on the rheological properties and filtration loss of polymer-based slurries at ultra-high temperatures (200 °C and 240 °C) are investigated by the American Petroleum Institute (API) standards. The results show that ionic liquids with different structures could improve the high-temperature rheological properties of polymer-based drilling fluids. The rheological parameter value (YP/PV) of the polymer-based slurry formulated with ILC is slightly higher than that with ILA at the same concentration, while the YP/PV value of the polymer-based slurry with ILA is slightly higher than that with ILB, which is consistent with the TGA thermal stability of ILA, ILB, and ILC; the thermal stability of ILC with pyrrolidine cations is higher than that of ILA with imidazole cations, and the thermal stability of ILA with bis(trifluorosulfonyl)amide anions is higher than that of ILB with tetrafluoroborate anions. Cation interlayer exchange between organic cation and sodium montmorillonite can improve the rheological properties of water-based drilling fluids. And meantime, the S=O bond in bis(trifluorosulfonyl)amide ions and the hydroxyl group of sodium montmorillonite may form hydrogen bonds, which also may increase the rheological properties of water-based drilling fluids. ILA, ILB, and ILC cannot reduce the filtration loss of polymer-based drilling fluids at ultra-high temperatures.

Anodic Cyclization Reactions and an Approach to the Chrysosporazine Family of Natural Products

Electrochemistry has long offered new opportunities for the construction of biologically relevant molecules. Many of these opportunities are based on the ability that electrochemistry provides for reversing the polarity of known functional groups. For example, consider the brief retrosynthetic analysis shown in the Scheme below. The analysis proposes a route to the Chrysosporazine family of natural products (specifically Chrysosporazine D in this case) from readily available amino acid and lignin derived starting materials. The Chrysosporazines are efflux inhibitors that improve the effectiveness of chemotherapy agents.1 The plan calls for a coupling of the two starting materials to afford a cyclization substrate. However, the proposed cyclization reaction would combine a nucleophilic amide nitrogen with a nucleophile electron rich styrene derivative. In principle, an anodic oxidation reaction can solve this issue by either converting the amide nitrogen into a radical or oxidizing the styrene derivative to form a radical cation. Either mode would effectively reverse the polarity of one of the nucleophilic groups and allow for the cyclization. Previous efforts examining these cyclizations have focused on the generation of a N-radical intermediate.2 Yet while these efforts have been very successful, they require the presence of a phenyl ring on the amide nitrogen in order to lower its pKa. This is essential for the formation of an amide anion that is in turn oxidized to the desired N-radical. Such a plan is not compatible with the synthesis of the Chrysosporazines that simply do not have a phenyl ring on the nitrogen of the amide. Placing one there would prevent the intramolecular cyclization. So, how can this problem be resolved? There are two possible answers to this question. One involves a change in the overall strategy that converts the amide into an electron-rich olefin equivalent that can be oxidized to from a radical cation. The second involves finding an alternative method for dropping the pKa of the amide so that the anion and subsequent N-radical can still be made. In the chemistry to be discussed, both strategies will be examined and the propensity for the cyclic product to undergo over-oxidation shown to be the determining factor for which pathway is preferred; a preference that has led to a new approach to N-based radical cyclizations. 1. Elbanna, A. H., Khalil, Z. G., Bernhardt, P., V., Capon, R. J. Org. Lett. 2019, 21, 8097–8100. 2. Xiong, P.; Xu, H-C. Acc. Chem. Res. 2019, 52, 3339-3350. Figure 1

Ethylene Carbonate-based Concentrated Electrolyte Composed of Asymmetric Amide Anion for Rechargeable Sodium-ion Batteries

Ethylene Carbonate-based Concentrated Electrolyte Composed of Asymmetric Amide Anion for Rechargeable Sodium-ion Batteries

Ammonothermal Synthesis and Crystal Structure of the Ternary Amide Na2Ba(NH2)4

AbstractThe ternary amide Na2Ba(NH2)4 was synthesized at ammonothermal conditions (870 K, 135 MPa) in custom‐built high‐pressure autoclaves. The compound was structurally characterized using X‐ray diffraction and crystallizes in space group Pccn (no. 56) with lattice parameters a=10.6492(2), b=7.8064(2) and c=8.1046(2) Å. To the best of our knowledge, the structure type has not yet been observed in any ternary amide before and can be described as a defective variant of the NaCl structure type. The presence of amide ions in the compound is verified by Fourier‐transform infrared (FTIR) spectroscopy and the experimental spectrum is compared to the theoretical spectrum obtained through density functional theory (DFT) calculations. Na2Ba(NH2)4 complements the range of reported ternary alkali metal alkaline‐earth metal amides with the smallest Shannon radius ratio of rA/AE=0.76. The influence of this ratio on the formation of the new structure type is discussed as well. The characterization of intermediate species such as this ternary amide extends the understanding of the ammonothermal synthesis and can be useful for synthetic control in the formation of nitrides at ammonothermal conditions.

Activation Energy of Ion Desorption at Ionic Liquid/Pt Electrode Interfaces: A Sum-Frequency Generation Vibrational Spectroscopic Study.

Electrolyte/electrode interfaces of room-temperature ionic liquids (RTILs) exhibit hysteretic responses to different applied potentials owing to the differences in the ion adsorption/desorption processes; the ion desorption requires excess potential, which reflects the activation energy of ion desorption. Thus far, the contributions of the ion adsorption energy and the activation barrier for ion desorption toward the ion-dependent excess potential have not been quantified. Herein, we report on our infrared-visible sum-frequency generation vibrational spectroscopy study of the hysteretic responses of the anion adsorption/desorption at Pt electrode interfaces using neat, binary, and diluted RTILs composed of 1-butyl-3-methylimidazolium cations ([C4mim]+) and bis(trifluoromethanesulfonyl)amide ([TFSA]-) and trifluoromethanesulfonate ([OTf]-) anions. Experimental results are compared to the theoretical calculations for the electric double layer model. The hysteretic response of the RTIL/Pt interface derives predominantly from the activation energy of anion desorption, which causes the negative excess potential required for anion desorption. A comparison of the anion adsorption/desorption behaviors of neat RTILs with those of binary and diluted RTILs reveals that the large activation energy of anion desorption at the neat RTIL/Pt interface originates largely from the activation barrier for restructuring ionic layering in the diffuse layer.

Exploring the Light-Emitting Agents in Renilla Luciferases by an Effective QM/MM Approach.

Bioluminescence is a fascinating natural phenomenon, wherein organisms produce light through specific biochemical reactions. Among these organisms, Renilla luciferase (RLuc) derived from the sea pansy Renilla reniformis is notable for its blue light emission and has potential applications in bioluminescent tagging. Our study focuses on RLuc8, a variant of RLuc with eight amino acid substitutions. Recent studies have shown that the luminescent emitter coelenteramide can adopt multiple protonation states, which may be influenced by nearby residues at the enzyme's active site, demonstrating a complex interplay between protein structure and bioluminescence. Herein, using the quantum mechanical consistent force field method and the semimacroscopic protein dipole-Langevin dipole method with linear response approximation, we show that the phenolate state of coelenteramide in RLuc8 is the primary light-emitting species in agreement with experimental results. Our calculations also suggest that the proton transfer (PT) from neutral coelenteramide to Asp162 plays a crucial role in the bioluminescence process. Additionally, we reproduced the observed emission maximum for the amide anion in RLuc8-D120A and the pyrazine anion in the presence of a Na+ counterion in RLuc8-D162A, suggesting that these are the primary emitters. Furthermore, our calculations on the neutral emitter in the engineered AncFT-D160A enzyme, structurally akin to RLuc8-D162A but with a considerably blue-shifted emission peak, aligned with the observed data, possibly explaining the variance in emission peaks. Overall, this study demonstrates an effective approach to investigate chromophores' bimolecular states while incorporating the PT process in emission spectra calculations, contributing valuable insights for future studies of PT in photoproteins.

Synthesis of Superbulky Amide Ligands by Addition of Polar Reagents to Sila-Imine.

The chemistry of extremely bulky amide ligands is troubled by difficulties in deprotonation of the parent amine. As an alternative route to superbulky amide reagents, the addition of polar reagents to a sila-imine has been investigated. Attempts to synthesize the superbulky amide anion (tBu3Si)2N- by addition of tBuLi to tBu2Si=N(SitBu3) failed and gave tBu3Si(tBu2HSi)NLi and isobutene. Reaction of the sila-imine with KOtBu successfully led to tBu3Si[tBu2(tBuO)Si]NK which crystallized as a separated ion-pair. Reaction with the slightly bulkier KOAd (Ad=1-adamantyl) led in presence of THF to ether ring-opening. Reaction with tBuOH gave tBu3Si[tBu2(tBuO)Si]NH but this amine cannot be easily deprotonated. Reaction with (BDI*)MgnBu in presence of THF gave (BDI*)Mg+ ⋅ (THF)2 and the non-coordinating anion tBu3Si[tBu2(nBu)Si]N-; BDI*=ß-diketiminate ligand HC[C(tBu)N-DIPP]2, DIPP=2,6-diisopropylphenyl. Reaction of Mg(nBu)2 with tBu2Si=N(SitBu3) led to a Mg complex with one amide ligand: tBu3Si[tBu2(nBu)Si]N-. The other superbulky amide anion isomerized by internal deprotonation of a tBu-substituent to give a primary carbanion that is also coordinated to Mg. Although the amide-to-carbanion isomerization is highly contrathermodynamic, it allows for coordination of both anions to a single Mg center. The new bulky amides are rare cases of halogen-free weakly coordinating anions.

Synthesis of Magnetic N‐Vinylformamide Grafted Starch and Its Application in Heavy Metals Adsorption

AbstractUsing cyclohexanone and sodium bromate as initiators, N‐vinylformamide (NVF) is self‐polymerized and grafted onto the pregelatinized starch (PGS) to form NVF‐starch graft copolymer (SGC). Fe3O4 surface is coated by MnO2 formed by in situ chemical reaction between KMnO4 and MnSO4 to obtain modified nanoparticles (NFs). A novel M‐starch graft copolymer (M‐SGC) is combined from SGC and NFs in aqueous solution by sonication. The structures of SGC, NFs, and M‐SGC are characterized by FTIR, SEM, XRD, BET, and 1H‐NMR. The adsorption mechanism by M‐SGC is investigated by FTIR and XPS. The results show that M‐SGC has the ability to adsorb Cu2+, Ni2+, and Cr2O72− from aqueous solutions with high efficiency. Cu2+ and Ni2+ are removed by amide bond chelation and ion exchange of M‐SGC. The Cr2O72− is separated by chelation through turned to trivalent chromium. M‐SGC adsorbs 274.6 mg g−1 Cu2+ in 3.0 g L−1 copper solution, 8.92 mg g−1 Ni2+ in 0.5 g L−1 nickel solution, and 36.5 mg g−1 Cr2O72− in 1.2 g L−1 potassium dichromate solution. The adsorption experiments of M‐SGC has a good recyclability.

PEGylated AIEgens for dual sensing of ATP and H2S and cancer cells photodynamic therapy

Fluorescent sensors have been widely applied for biosensing, but probes for both multiple analytes sensing and photodynamic therapy (PDT) effect are less reported. In this article, we reported three AIE-based probes anchored with different mass-weight polyethylene glycol (PEG) tails, i.e., TPE-PEG160, TPE-PEG350, and TPE-PEG750, for both adenosine-5′-triphosphate (ATP) and hydrogen sulfide (H2S) detection and also cancer cells photodynamic therapy. TPE-PEGns (n = 160, 350 and 750) contain the tetraphenylethylene-based fluorophore core, the pyridinium and amide anion binding sites, the H2S cleavable disulfide bond, and the hydrophilic PEG chain. They exhibit a good amphiphilic property and can self-assemble nona-aggregation with a moderated red emission in an aqueous solution. Importantly, the size of aggregation, photophysical property, sensing ability and photosensitivity of these amphiphilic probes can be controlled by tuning the PEG chain length. Moreover, the selected probe TPE-PEG160 has been successfully used to detect environmental H2S and image ATP levels in living cells, and TPE-PEG750 has been used for photodynamic therapy of tumor cells under light irradiation.

Solvent-free transformation of protic ionic liquids into zwitterions.

We synthesized several protic ionic liquids (ILs) composed of onium cations and the (trifluoromethylsulfonyl)(vinylsulfonyl)amide anion. The addition of a base catalytically facilitated their transformation into zwitterions (ZIs) under solvent-free conditions, which is a convenient method for synthesizing ZIs from ILs.

S-Block metal complexes of superbulky (tBu3Si)2N-: a new weakly coordinating anion?

Sterically hindered amide anions have found widespread application as deprotonation agents or as ligands to stabilize metals in unusual coordination geometries or oxidation states. The use of bulky amides has also been advantageous in catalyst design. Herein we present s-block metal chemistry with one of the bulkiest known amide ligands: (tBu3Si)2N- (abbreviated: tBuN-). The parent amine (tBuNH), introduced earlier by Wiberg, is extremely resistant to deprotonation (even with nBuLi/KOtBu superbases) but can be deprotonated slowly with a blue Cs+/e- electride formed by addition of Cs0 to THF. (tBuN)Cs crystallized as a separated ion-pair, even without cocrystallized solvent. As salt-metathesis reactions with (tBuN)Cs are sluggish and incomplete, it has only limited use as an amide transfer reagent. However, ball-milling with LiI led to quantitative formation of (tBuN)Li and CsI. Structural characterization shows that (tBuN)Li is a monomeric contact ion-pair with a relatively short N-Li bond, an unusual T-shaped coordination geometry around N and extremely short Li⋯Me anagostic interactions. Crystal structures are compared with Li and Cs complexes of less bulky amide ligands (iPr3Si)2N- (iPrN-) and (Me3Si)2N- (MeN-). DFT calculations show trends in the geometries and electron distributions of amide ligands of increasing steric bulk (MeN- < iPrN- < tBuN-) and confirm that tBuN- is a rare example of a halogen-free weakly coordinating anion.

Molecular Level Origin of Ion Dynamics in Highly Concentrated Electrolytes.

Single-ion conducting liquid electrolytes are key to achieving rapid charge/discharge in Li secondary batteries. The Li+ transference (or transport) numbers are the defining properties of such electrolytes and have been discussed in the framework of concentrated solution theories. However, the connection between macroscopic transference and microscopic ion dynamics remains unclear. Molecular dynamics simulations were performed to obtain direct information regarding the microscopic behaviors in highly concentrated electrolytes, and the relationships between these behaviors and the transference number were determined under anion-blocking conditions. Various solvents with different donor numbers (DNs) were used along with a Li salt of the weakly Lewis basic bis(fluorosulfonyl)amide anion for electrolyte preparation. Favorable ordered Li+ structuring and a continuous Li+ conduction pathway were observed for the fluoroethylene carbonate-based electrolyte due to its low DN. The properties were less pronounced at higher DNs, e.g., for the dimethyl sulfoxide-based electrolyte. The τLi-solventlife/τdipolerelax ratio was introduced as a factor for ion dynamics, and the two mechanisms of ion transport were considered an exchange mechanism (τLi-solventlife/τdipolerelax < 1) and a vehicle mechanism (translational motion of solvated Li+) (τLi-solventlife/τdipolerelax ≥ 1). Vehicle-type transport was dominant with high DNs, while exchangeable transport was preferable at lower DNs. These findings should aid the further selection of solvents and Li salts to prepare single-ion conducting electrolytes.

Fatty Acid-Activated Proton Transport by Bisaryl Anion Transporters Depolarises Mitochondria and Reduces the Viability of MDA-MB-231 Breast Cancer Cells.

In respiring mitochondria, the proton gradient across the inner mitochondrial membrane is used to drive ATP production. Mitochondrial uncouplers, which are typically weak acid protonophores, can disrupt this process to induce mitochondrial dysfunction and apoptosis in cancer cells. We have shown that bisaryl urea-based anion transporters can also mediate mitochondrial uncoupling through a novel fatty acid-activated proton transport mechanism, where the bisaryl urea promotes the transbilayer movement of deprotonated fatty acids and proton transport. In this paper, we investigated the impact of replacing the urea group with squaramide, amide and diurea anion binding motifs. Bisaryl squaramides were found to depolarise mitochondria and reduce MDA-MB-231 breast cancer cell viability to similar extents as their urea counterpart. Bisaryl amides and diureas were less active and required higher concentrations to produce these effects. For all scaffolds, the substitution of the bisaryl rings with lipophilic electron-withdrawing groups was required for activity. An investigation of the proton transport mechanism in vesicles showed that active compounds participate in fatty acid-activated proton transport, except for a squaramide analogue, which was sufficiently acidic to act as a classical protonophore and transport protons in the absence of free fatty acids.

Nonlinear optical properties, structural and transition state analyses of ionic liquids: DFT and DFT-D2/D3 studies

This paper includes the structural properties, transition state analysis and NLO properties of the ionic liquids in quantum chemical calculations. Hydrogen bond geometries calculated by B3LYP and ωB97XD approaches have been compared with the crystallographic data in the literature. Transition state analysis have been carried out using Synchronous Transit-Guided Quasi-Newton (STQN) method with QST2 option and Density Functional Theory. Forms according to the positions of the proton on hydrogen bond axes and transition states have been evaluated by relative energy scanning. Interactions between anions and cations in ionic liquids optimizations have been studied by CP approach with D2 and D3 versions of Grimme’s dispersion correction. Electric dipole moments, dipole polarizability, first and second dipole hyper polarizability and important components have been calculated, statically and dynamically for ionic liquids. Effective and stable structures in terms of NLO have been evaluated. In addition, B3LYP and ωB97XD functionals approaches have been tested considering Grimme’s D2/D3 dispersion models for lithium interactions with bis(trifluoromethanesulfonyl)amide and methylsulfonate anions.

Amide-Based Ionic Liquid Electrolytes for Alkali-Metal-Ion Rechargeable Batteries.

Ionic liquids (ILs) have a wide variety of applications in energy storage and material production. ILs are composed of only cations and anions, without any molecular solvents, and are generally known as "designer liquids (solvents)" because their physicochemical properties can be tuned by the combination of ionic species. In recent several decades, research and development activities of rechargeable batteries have garnered considerable attention because certain groups of ILs exhibit high electrochemical stability and moderate ionic conductivity, rendering them suitable for application in high-voltage batteries. ILs with amide anions are representative electrolytes and are extensively researched by many research groups, including our group. This paper focuses on amide-based ILs as electrolytes for alkali-metal-ion rechargeable batteries, introducing their history, characteristics, and existing challenges to be addressed.

Optimization of lead (II) removal from water and wastewater using a novel magnetic nanocomposite of aminopropyl triethoxysilane coated with carboxymethyl cellulose cross-linked with chitosan nanoparticles

The removal of heavy metals from industrial wastewater is nowadays one of the most interesting challenges in water remediation using adsorbent nanomaterials. The present study presents a novel adsorbent (Fe3O4@CS@CMC-SiNH2) nanocomposite (NC), by functionalization of the carboxymethyl cellulose (CMC) cross-linked to magnetic chitosan nanoparticles (Fe3O4@CS NPs) with aminopropyl triethoxysilane layer (APTES), and evaluate its performance toward lead (II) removal from wastewater. The synthesized NCs were characterized using several techniques. The optimization of the adsorption process was performed using the Response Surface Methodology with the Box-Behnken Design model. The optimal conditions for lead (II) ion removal were found to be; pH of 5.1, a dose of 0.10 g/L, and a temperature of 36 ℃ using Fe3O4@CS@CMC-SiNH2 NCs which proved to have superior adsorption performance with a maximum adsorption capacity of 555.56 mgPb(II)/gNC, and fast achievement of the adsorption equilibrium (30 min). Favorable monolayer chemisorption was estimated and proved to be a coordination bond between the NH amide and lead (II) ions using FTIR, as well as up to seven adsorption–desorption cycles were effective for lead (II) ion removal from aqueous solutions. In addition, the Fe3O4@CS@CMC-SiNH2 NCs showed 98.10%, and 97.21 % removal of lead (II) ions in the absence, and the presence of other contaminants of heavy metals such as cadmium (II) and mercury (II). Moreover, the Fe3O4@CS@CMC-SiNH2 NC exhibited high efficiency in the removal of lead (II) ions from wastewater, can be easily separated from water by magnetic separation, showed satisfactory reusability for five cycles of the adsorption–desorption process of lead (II) ion removal from tap water and wastewater. Consequently, Fe3O4@CS@CMC-SiNH2 NC is a prospective adsorbent nanomaterial for lead (II) ions removal from wastewater.

Mechanism of Heterogeneous Alkaline Deacetylation of Chitin: A Review.

This review provides an analysis of experimental results on the study of alkaline heterogeneous deacetylation of chitin obtained by the authors and also published in the literature. A detailed analysis of the reaction kinetics was carried out considering the influence of numerous factors: reaction reversibility, crystallinity and porosity of chitin, changes in chitin morphology during washing, alkali concentration, diffusion of hydroxide ions, and hydration of reacting particles. A mechanism for the chitin deacetylation reaction is proposed, taking into account its kinetic features in which the decisive role is assigned to the effects of hydration. It has been shown that the rate of chitin deacetylation increases with a decrease in the degree of hydration of hydroxide ions in a concentrated alkali solution. When the alkali concentration is less than the limit of complete hydration, the reaction practically does not occur. Hypotheses have been put forward to explain the decrease in the rate of the reaction in the second flat portion of the kinetic curve. The first hypothesis is the formation of "free" water, leading to the hydration of chitin molecules and a decrease in the reaction rate. The second hypothesis postulates the formation of a stable amide anion of chitosan, which prevents the nucleophilic attack of the chitin macromolecule by hydroxide ions.

One-Pot Syntheses of PET-Based Plasticizer and Tetramethyl Thiuram Monosulfide (TMTS) as Vulcanization Accelerator for Rubber Production

Styrene-butadiene (SBR) and acrylonitrile-butadiene (NBR) rubber blends with tetramethyl thiuram disulfide (TMTD) and tetramethyl thiuram monosulfide (TMTS) accelerators and environmentally friendly plasticizers, obtained from PET recycling and biobased resources (LA/PG/PET/EG/LA), were prepared. The mechanical properties of the obtained rubber products were tested and compared with those of commercial dioctyl terephthalate (DOTP). TMTS was prepared by simple and efficient one-pot synthesis from dimethylamine, carbon disulfide, potassium cyanide, and ammonium chloride as catalysts in recycled isopropanol/water azeotrope as solvent. In a comparative study, methoxide, ethoxide, iodide, and amide ions were also used. The two-step reaction mechanism of TMTS synthesis involves the oxidation of the amine salt of dimethyldithiocarbamic acid to TMTD by hydrogen peroxide and sulfur elimination from the TMTD disulfide bond. Potassium cyanide appears to be the most efficient nucleophile. The simplicity of operation, mild reaction conditions, solvent recycling, high yields, and applicability to the industrial level are the advantages of this process. Shore hardness, tensile strength, and compression test results of vulcanized blends before and after aging showed similar properties for both accelerators, while somewhat better results were obtained with LA/PG/PET/EG/LA plasticizer.