Ethyl Substituents Research Articles

Synthesis of alkyl derivatives of 3,7,10-trioxo-2,4,6,8,9,11-hexaaza[3.3.3]propellane and evaluation of their biological activity

Today 3,7,10-trioxo-2,4,6,8,9,11-hexaaaza[3.3.3]propellane (THAP) has not yet received widespread re-search attention due to the complexity of the synthesis. This work is devoted to the development of a method for the THAP derivatives synthesis, as well as to the study of their biological activity in comparison with al-kyl-substituted glycolurils (subject of comparison). ТНАРwas N-alkylated to furnish novel hexaalkyl deriva-tives of ТНАРwith methyl, ethyl and propyl substituents. The conditionsfor obtaining the maximum yield of the target productwere optimizedon the base of methyl derivative. The reaction proceeded in DMSO/КОНat 75–80ºC for 13hours in a moderate yield of 56%. The ethyl and propyl derivatives of ТНАРwere synthe-sized under the same conditions. The biological activity of the obtained ТНАРalkyl derivatives and glycoluril alkyl derivatives was evaluated against Sporosarcina ureae, Bacillus pumilus, Salmonella typhimurium and Staphylococcus aureus bacteria and influenza A virus. All the samples were found to exhib-it antibacterial activity against Staphylococcus aureus.It was shown that 2,4,6,8,9,11-hexapropyl-ТНАР, di-tert-butyl-diphenyl-, di-tert-butyl-dibenzyl-, di-tert-butyl-dimethyl-and di-isopropyl-dibenzylglycoluril, have exhibited also toxicity to living cells besides antiviral activity

Influence factors on CO2 solubility in cycloalkanes and cycloalkane volume expansion: Temperature, pressure and molecular structure

In CO2 enhanced oil recovery process, the interactions between CO2 and oil components are complex since crude oil is a mixture of n-alkanes, cycloalkanes, aromatics, resin, asphaltene and other compounds. To investigate the effects of temperature, pressure and molecular structure on CO2 solubility in cycloalkanes and the resulting cycloalkane volume expansion, the solubility of near critical and supercritical CO2 in cyclopentane (CP), cyclohexane (CH), methylcyclohexane (MCH), methylcyclopentane (MCP) and ethylcyclohexane (ECH) and the volume expansion factor of cycloalkanes at diverse temperature and pressure were measured. It was observed that increasing temperature decreases CO2 solubility, while CO2 solubility increases with pressure increasing. Compared with CP and CH, it's harder for CO2 to dissolve in their methyl or ethyl substituents. For homologues, CO2 solubility decreases with carbon number increasing. The volume expansion factor and solubility have a same variation tendency with temperature, pressure and molecular structure. The experimental results of solubility were correlated with Fornari's model and PR equation of state with the maximum average absolute relative deviation (AARD) of 2.8% and 6.8%, respectively. The excess molar volume of CO2 + cycloalkane mixtures was calculated to be negative and increases with pressure.

Computational and Experimental Method for Evaluating the Reactivity of Substituted Toluene Diamines and Azo Compounds in the Reactions of Amine and Anhydride Curing of Epoxy Resins

The optimization of the molecular structure of substituted 3,5-toluylene diamines was carried out by the ab initio method, which made it possible to calculate the volume of stretching vibrations and the steric factor of the ethyl and methylthiol substituents on the basis of the data obtained on the bond lengths and bond angles. A linear dependence of the total steric factor of substituents in the molecules of substituted 3,5-toluylene diamines on the activation energy of the reaction of their polyaddition with novolac epoxy resin was established. For 4-phenylazophenol, 4-methoxyazobenzene, 4-phenylazo-N,N ʹ-dimethylaniline, 1-(2-pyridylazo)-2-naphthol, phenylazo-4-naphthylamine, studied as catalysts for the polyaddition of isomethyltetrahydrophthalic anhydride to epoxy resin, dependence of the activation energy on the value of the electron density is observed at the nitrogen atom of the azo group. The derived linear dependences evidence the established latency of epoxy binders, which depends mainly on hardeners and catalysts. Using a computational and experimental method for evaluating the reactivity of hardeners and catalysts, heat-resistant polymers and composites with good physical-mechanical and thermomechanical characteristics were produced, which meet modern requirements for products operating in a wide temperature range.

Singlet Fission in Thin Solid Films of Bis(thienyl)diketopyrrolopyrroles.

The singlet fission (SF) process discovered in bis(thienyl)diketopyrrolopyrroles (TDPPs) can boost their potential for photovoltaics (PV). The crystal structures of TDPP analogs carrying n-hexyl, n-butyl, or 2-(adamant-1-yl)ethyl substituents are similar, but contain increasingly slipped stacked neighbor molecules. The observed SF rate constants, kSF , (7±4), (9±3) and (5.6±1.9) ns-1 for thin films of the three compounds, respectively, are roughly equal, but the triplet quantum yields vary strongly: (120±40), (160±40) and (70±16), respectively. The recent molecular pair model reproduces the near equality of all three kSF at the crystal geometries and identifies all possible pair arrangements in which SF is predicted to be faster, by up to two orders of magnitude. However, it is also clear that the presently non-existent ability to predict the rates of processes competing with SF is pivotal for providing a guide for efforts to optimize the materials for PV.

Synthetic naphthoquinones thioglucosides as potential candidates to antivirals

Background: Human alphaherpesvirus 1 (HSV-1) is a one of a widespread human pathogen with Herpes labialis as most common clinical form. The nucleoside inhibitors of DNA polymerase are available for treatment of HSV-1 infection but their undesirable adverse effects and emergence of drug-resistant strains highlight the need to search new effective antivirals. The aim of our study was to improve solubility of structural analogues of naphthoquinonoid pigment of sea urchins echinochrome A (Ech) which antiviral activity against HSV-1 have been demonstrated previously. Methods and materials: The conjugation of naphthoquinones with non-toxic carbohydrate, thioglucose, have resulted in a number of compounds distinguished by presence of methyl-, ethyl, or hydroxyl-groups in defined position. Anti-HSV-1 activity of six thioglucosides (TGs) was analyzed on the different stages of L-2 strain of HSV-1 replication in the Vero E cells with help of MTT-test and calculation of half maximal inhibitory concentrations (IC50) and selectivity indexes. Acyclovir and echinochrome A were used as reference drugs. Results: Cytotoxity of new hydroxy- and alkyl dithioglucoside structures was 1.5–2 times less than the cytotoxity of Ech. When mode of TG action was studied, in simultaneous treatment of cells by virus + TG mixture, the TG-Et showed lowest among all TG and Ech value of IC50 (219.0 ± 46.0 vs. 246.8 ± 44.5 of Ech) and highest SI (1.9 ± 0.3 vs. 0.8 ± 0.1 of Ech). TG-Et also has more significant virulicidal effect with IC50 = 86.2 ± 12.9 and SI = 2.7 ± 0.5, compare with echinochrome (214.7 ± 36.6 and 0.9 ± 0.2, respectively). However, the pretreatment of uninfected cells and treatment of HSV-1-infected cells by TG-Et, TG-Me, and TG-OH has now effect, whereas when one Et-group was added to TG-Et, or Et-group was substituted by phenyl-group, the modified compounds became permeable to infected cells and showed good antiviral toward infected cells. Conclusion: Thus, we suggest that main anti-HSV-1 effect of new synthetic thioglucoside derivates of natural naphthoquinones is related to their virulicidal action, and TG with a lipophilic ethyl substituent more easily penetrate to virus envelope. The additional increase of lipophilic capacity improves the permeability into infected cells and such modifications may be very useful for development of new effective drugs with broad spectrum of antiviral activity.

Cytotoxic activity and apoptosis induction by a series Ag(I)-NHC complexes on human breast cancer cells and non-tumorigenic epithelial cell line

The main problems encountered in treatment with anticancer drugs, undesired side effects, and toxicity. One of the most important parameters in cell transport is the lipophilic and solubility property of the drug. Enough with the potential effects, side effects with minimal demand for new anticancer compounds, mechanisms of action of the compound can meet because of increased efforts to be clarified. In this case, scientists were encouraged to do new research. In particular, the organometallic compounds are one of the topics focused lately. Ag(I)-NHC complexes are one of the most important classes of organometallic compounds. Although the anticancer activity of Ag(I)-NHC complexes have been known recently times, the anticancer effects of 2-morpholino ethyl substituted benzimidazolium derivative, lipophilic, and solubility properties. Ag(I)-NHC complexes have not unknown yet. Therefore, we aimed to investigate of cytotoxic effect and apoptosis mechanism on breast cancer cell lines (MCF7), breast adenocarcinoma cell lines (MDA-MB-231), and non-tumorigenic epithelium cell lines (MCF 10A) of new Ag(I)-NHC complexes that derivative from morpholine-linked benzimidazole, were synthesized and antimicrobial activity was determined in our previous study. The cytotoxicity was determined by the MTS method, and the apoptosis mechanisms were determined the cell cycle, Annexin V, and caspase-3 analysis. A new benzimidazolium salt bearing morpholino ethyl substituent (2) was synthesized. This benzimidazolium salt was characterized by NMR and FT-IR spectroscopic method and elemental analysis technique. Also, the structure of the new benzimidazolium salt was confirmed by single-crystal X-ray diffraction. Ag(I)-NHC complexes inhibited the growth of MCF7 and MDA-MB-231 cells depending on the dosage and time. The complexes 3a and 3b exhibited a significant difference p < 0.05; p < 0.001; and p < 0.001 level depend on depending on the increase in concentration on cancer cells. All compound induced by apoptosis was associated with stopping the cell cycle in phase G1 and the caspase-3 activity exhibited. The complex 3c was the lowest number of caspase-activating cells (2.1%) compared with both the control and other complexes in MDA-MB-231 cells. But the complex 3a was the highest number of caspase-activating cells (% 9.6). These findings have shown that these new Ag(I)-NHC complexes can be important new anticancer agents for breast cancer treatments.

Synthesis and structures of amido-functionalized N-heterocyclic nickel(II) carbene complexes

A series of bis-bidentate nickel(II) complexes [Ni(R-bimy-CH2CONH)2] (bimyH = benzimidazole; R = Me (3), Et (4), Ph (5)) bearing amido-functionalized N-heterocyclic carbene ligands, and pincer-type nickel(II) complexes [Ni(Py-bimy-CH2CONH)X] (X = Cl (6), Br (7)) bearing an amido- and pyridyl-functionalized N-heterocyclic carbene ligand were prepared. These complexes were characterized by NMR (1D and 2D) and single-crystal X-ray diffraction. Complexes 3-5 possess cis configuration, and the carbene ligands bound to the nickel atom through C2 carbon and NH nitrogen in a bis-bidentate coordination mode. In complexes 6 and 7, the pyridyl substituent was also N-bound to the nickel metal center resulting in a pincer-type coordination mode. As observed from the proton NMR spectra, the six-membered chelate rings in complexes 3-5 rendered the protons of the methylene moieties diastereotopic, and the cis configuration made the free rotation of the ethyl substituent in 4 and the phenyl substituent in 5 hampered by the adjacent substituent. The catalytic activity of these nickel complexes in Kumada cross-coupling of phenylmagnesium bromide with aryl chlorides was also investigated. The results indicated that pincer-type complexes 6 and 7 displayed excellent to moderate catalytic activity depending on the aryl chloride used.

Tuning the intermolecular interaction of A2-A1-D-A1-A2 type non-fullerene acceptors by substituent engineering for organic solar cells with ultrahigh VOC of ~1.2 V

For non-fullerene acceptors (NFAs) with linear A2-A1-D-A1-A2 backbone, there are three kinds of possible intermolecular interaction, A1-A1, A1-A2 and A2-A2 stacking. Hence, it is a huge challenge to control this interaction and investigate the effect of intermolecular stacking model on the photovoltaic performance. Here, we adopt a feasible strategy, by utilizing different substituent groups on terminal A2 unit of dicyanomethylene rhodanine (RCN), to modulate this stacking model. According to theoretical calculation results, the molecule BTA3 with ethyl substituent packs via heterogeneous interaction between A2 and A1 unit in neighboring molecules. Surprisingly, the benzyl group can effectively transform the aggregation of BTA5 into homogeneous packing of A2-A2 model, which might be driven by the strong interaction between benzyl and A1 (benzotriazole) unit. However, different with benzyl, phenyl end group impedes the intermolecular interaction of BTA4 due to the large steric hindrance. When using a BTA-based D-π-A polymer J52-F as donor according to “Same-A-Strategy”, BTA3-5 could achieve ultrahigh open-circuit voltage (VOC) of 1.17–1.21 V. Finally, BTA5 with benzyl groups realized an improved power conversion efficiency (PCE) of 11.27%, obviously higher than that of BTA3 (PCE=9.04%) and BTA4 (PCE=5.61%). It is also worth noting that the same trend can be found when using other four classic p-type polymers of P3HT, PTB7, PTB7-Th and PBDB-T. This work not only investigates the intermolecular interaction of A2-A1-D-A1-A2 type NFAs for the first time, but also provides a straightforward and universal method to change the interaction model and improve the photovoltaic performance.

Cholesterol and Sitosterol, Two Members of the Steroid Family That Differ in Structure by a Single Ethyl Group Yet Maintain the Right Balance between Plant and Animal Kingdoms

Cholesterol and sitosterol are two members of the steroid family, which molecular structures differ only by the presence of an ethyl substituent at the position 24 of the steroid skeleton. Cholesterol is mainly synthesized in large quantities in the liver of animals and only in small quantities by plants. In contrast sitosterol is only synthesized by plants. This tiny difference of an ethyl group between the two steroids structures have induced profound effects on the climatic changes during evolution, but plant sterols still have important effects on cholesterol metabolism on humans.

Approach to the Core Structure of Streptosetin A

AbstractStreptosetin A belongs to the 3‐decalinoyltetramic acids. In contrast to most of other known natural products of this type, the decalin part features a β‐hydroxyketone subunit, making an intramolecular cycloaddition approach less suitable. We examined an approach where the decalin part would be fashioned by an intramolecular aldol addition. By using a Diels‐Alder reaction between the Rawal diene and a substituted methacrylate, a cyclohexanone was obtained. An organocuprate addition introduced the ethyl substituent before, the side chain was converted to an enal. However, contrary to our expectations, the aldol reaction led to the condensation product. Other routes to reach the key cyclohexanone were also investigated.

Unexpected rapid aerobic transformation of 2,2,6,6-tetraethyl-4-oxo(piperidin-1-yloxyl) radical by cytochrome P450 in the presence of NADPH: Evidence against a simple reduction of the nitroxide moiety to the hydroxylamine

Aminoxyl radicals (nitroxides) are a class of compounds with important biomedical applications, serving as antioxidants, spin labels for proteins, spin probes of oximetry, pH, or redox status in electron paramagnetic resonance (EPR), or as contrast agents in magnetic resonance imaging (MRI). However, the fast reduction of the radical moiety in common tetramethyl-substituted cyclic nitroxides within cells, yielding diamagnetic hydroxylamines, limits their use in spectroscopic and imaging studies. In vivo half-lives of commonly used tetramethyl-substituted nitroxides span no more than a few minutes. Therefore, synthetic efforts have focused on enhancing the nitroxide stability towards reduction by varying the electronic and steric environment of the radical. Tetraethyl-substitution at alpha position to the aminoxyl function proved efficient in vitro against reduction by ascorbate or cytosolic extracts. Moreover, 2,2,6,6-tetraethyl-4-oxo(piperidin-1-yloxyl) radical (TEEPONE) was used successfully for tridimensional EPR and MRI in vivo imaging of mouse head, with a reported half-life of over 80 min. We decided to investigate the stability of tetraethyl-substituted piperidine nitroxides in the presence of hepatic microsomal fractions, since no detailed study of their “metabolic stability” at the molecular level had been reported despite examples of the use of these nitroxides in vivo. In this context, the rapid aerobic transformation of TEEPONE observed in the presence of rat liver microsomal fractions and NADPH was unexpected. Combining EPR, HPLC-HRMS, and DFT studies on a series of piperidine nitroxides — TEEPONE, 4-oxo-2,2,6,6-tetramethyl(piperidin-1-yloxyl) (TEMPONE), and 2,2,6,6-tetraethyl-4-hydroxy(piperidin-1-yloxyl) (TEEPOL), we propose that the rapid loss in paramagnetic character of TEEPONE is not due to reduction to hydroxylamine but is a consequence of carbon backbone modification initiated by hydrogen radical abstraction in alpha position to the carbonyl by the P450-Fe(V)=O species. Besides, hydrogen radical abstraction by P450 on ethyl substituents, leading to dehydrogenation or hydroxylation products, leaves the aminoxyl function intact but could alter the linewidth of the EPR signal and thus interfere with methods relying on measurement of this parameter (EPR oximetry).

Design and Synthesis of Novel 1a,3,4-Oxadiazole Derivatives as Cytotoxic Agents: A Combined Experimental and Docking Study

A novel series of 3,5-disubstituted-1a,3,4-oxadiazole derivatives was synthesized and screened for in vitro anticancer activity. The newly synthesized compounds were characterized by 1H, 13C NMR, IR spectroscopy and mass spectrometry. Among all the synthesized compounds, Oxaprozin derivatives containing 1,3,4-oxadiazole ring with 4-fluorobenzyl, 4-methoxybenzyl, methyl, and butyl substituents showed promising anticancer activity against HTB-57 cancer cell line, and derivatives with 4-fluorobenzyl, 4-methoxybenzyl, and propyl substituents exhibited a higher anticancer activity against a PPC-1 cell line. The possible binding mode interactions of the synthesized compounds with the key active site of the proline rich tyrosine kinase 2 Pyk2 receptor (PDB ID: 5TO8) were investigated using the AutoDock 4.2 docking protocol to find that the 1,3,4-oxadiazole Oxaprozin derivatives with methyl, ethyl, and propyl substituents had the highest binding energies (ΔG = –7.8, –7.6, and –6.8 kcal/mol, respectively) with Glu441, Leu431, Ala455, Val487, Met502, Leu556, Lys457, and Glu509.

Experimental and theoretical studies of the doubly substituted methyl-ethyl Criegee intermediate: Infrared action spectroscopy and unimolecular decay to OH radical products.

The infrared (IR) action spectrum of the doubly substituted methyl-ethyl Criegee intermediate (MECI) is observed in the CH stretch overtone region with detection of OH products. The MECI exhibits four conformers, all of which undergo unimolecular decay via a 1,4 H-atom transfer mechanism, followed by the rapid release of OH products. Conformers with different orientations of the carbonyl oxide group with respect to the methyl and ethyl substituents (i.e., anti and syn) decay via distinct transition state barriers (16.1 kcal mol-1 and 15.4 kcal mol-1, respectively). The observed IR action spectrum is in good agreement with the predicted anharmonic IR absorption spectrum, but exhibits significant congestion, which is attributed to couplings between spectroscopic bright states and nearby dark states. Energy-dependent OH appearance rates are measured upon IR excitation of the strongest features in the IR action spectrum and are found to be on the order of 106-107 s-1. The experimental rates are in good agreement with computed Rice-Ramsperger-Kassel-Marcus rates for the unimolecular decay of MECI at these energies, which incorporate quantum mechanical tunneling and sophisticated hindered rotor treatments, as well as high-level theoretical calculations of the TS barrier heights, rovibrational properties, and torsional barriers associated with the MECI conformers. Master equation modeling is used to predict thermal rates for the unimolecular decay of anti- and syn-MECI of 473 s-1 and 660 s-1, respectively. Comparison with other previously studied Criegee intermediate systems provides insights into substituent effects on unimolecular decay under both energy-dependent and thermal conditions.

Rotational spectra and molecular structures of ethylanilines

The molecular structures of three ethylanilines, ortho-, meta- and para-ethylaniline, have been obtained by means of Fourier-transform microwave spectroscopy. Rotational spectra of all three molecules display the nuclear quadrupole hyperfine structures arising from the 14N nucleus. Comparison of the determined structures allows a direct study of the influence of the position of the ethyl substituent on the structure of the amino group communicated through the phenyl ring.

Optimizing the monomer structure of polyhedral oligomeric silsesquioxane for ion transport in hybrid organic–inorganic block copolymers

ABSTRACTPoly(ethylene oxide)‐b‐polyhedral oligomeric silsesquioxane (PEO–POSS) mixed with lithium bis(trifluoromethanesulfonyl)imide salt is a nanostructured hybrid organic–inorganic block copolymer electrolyte that may enable lithium metal batteries. The synthesis and characteristics of three PEO–POSS block copolymer electrolytes which only differ by their POSS silica cage substituents (ethyl, isobutyl, and isooctyl) is reported. Changing the POSS monomer structure results in differences in both thermodynamics and ion transport. All three neat polymers exhibit lamellar morphologies. Adding salt results in the formation of a disordered window which closes and gives way to lamellae at higher salt concentrations. The width of disordered window decreases with increasing length of the POSS alkyl chain substituent from ethyl to isobutyl and is absent in the isooctyl sample. Rheological measurements demonstrate good mechanical rigidity when compared with similar all‐organic block copolymers. While salt diffusion coefficient and current ratio are unaffected by substituent length, ionic conductivity increases as the length of the alkyl chain substituent decreases: the ethyl substituent is optimal for ion transport. This is surprising because conventional wisdom suggests that ion transport occurs primarily in the PEO‐rich domains, that is, ion transport should be unaffected by substituent length after accounting for the minor change in conducting phase volume fraction. © 2020 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2020 © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 363–371

Cadalenes and norcadalenes in organic-rich shales of the Permian Irati Formation (Paraná Basin, Brazil): Tracers for terrestrial input or also indicators of temperature-controlled organic-inorganic interactions?

Cadalene, isocadalene and a series of norcadalenes were identified in black shales of the Permian Irati Formation in the northeastern and central eastern Paraná Basin (Brazil). The origin of their α-isomers with an isopropyl substituent is potentially related to higher plants, and likely reflects the spreading of pteridophytes and gymnosperms after the glaciation of southern Gondwana. A general increase in the relative abundance of isocadalene (1,6-dimethyl-3-isopropylnaphthalene, the β-isomer) co-occurs in with increasing thermal maturity at the base of the Amaral Machado Quarry (northeastern basin), and refers to the acid-catalyzed rearrangement of cadalene (1,6-dimethyl-4-isopropylnaphthalene, the α-isomer) due to the presence of montmorillonite, via an organic-inorganic interaction. This localized and incipient maturation can be related to diabase sills of the Serra Geral Formation. Similar maturation due to heating also affected the distribution of the norcadalenes by thermally stabilizing their α-isomers with an isopropyl substituent, in addition to the formation of related compounds with an ethyl substituent. Based on this, a norcadalene ratio is proposed, which is the sum of the 1,6-dimethyl-4-ethylnaphthalene and 1,6-dimethyl-3-ethylnaphthalene over the sum of the 1-isopropyl-4-methylnaphthalene and 1-isopropyl-7-methylnaphthalene. The results of this ratio and the established cadalene ratio resemble each other whereas samples from the São Mateus do Sul Quarry (central eastern basin) were not affected by thermal maturation and are characterized by a uniform distribution of the cadalenes and norcadalenes.

Perethylated pillar[n]arenes versus pillar[n]arenes: theoretical perspectives.

In this article we obtain the electronic structure, 1H NMR, and the vibrational spectra of perethylated pillar[n]arene (EtPn) (n = 5-8, 10) macrocycles using the ωB97x-based density functional theory. A single cavitand structure endowed with the robust pillar-like architecture was derived for the EtPn (n = 5-7) hosts while for the EtP8 receptor, two conformers one possessing the single cavitand and other double cavitand structure having four hydroquinone monomeric units in each cavity were obtained as the local minima. A double cavitand conformer of the EtP8 was found to be ~ 50kJmol-1 lower in energy than the single cavitand one which was attributed to the increased hydrogen bonding cooperativity and attractive H-H interactions. Further increase of hydroquinone monomers as in EtP10 host engenders only the double cavitand structure, composed of five hydroquinone monomeric units in each cavity. The molecular electrostatic potential investigations along the EtPn series of hosts reveal large electron-rich aromatic moieties compared to unsubstituted pillararenes which suggest the EtPn to be better artificial receptors toward cationic or neutral guests than their unsubstituted analogs. Calculated vibrational frequencies of EtPn (n = 5-8) show the cooperative stretching vibrations in a narrow span of 3241cm-1 to 3228cm-1. Besides, the most deshielded signals from aromatic protons along the EtPn (n = 5-8) series show up near 7.35ppm in their 1H NMR spectra. An increased cooperativity in the lowest energy of the EtP8 conformer further is evident from up-field signal corresponding to methylene protons of ethyl substituent compared with the single cavitand structure. Graphical abstractMolecular electrostatic potential for EtP5 and correlations obtained for δH VsρBCP and ν Vs G(r) plots.

Comparison of Cinchona Catalysts Containing Ethyl or Vinyl or Ethynyl Group at Their Quinuclidine Ring.

Numerous cinchona organocatalysts with different substituents at their quinuclidine unit have been described and tested, but the effect of those saturation has not been examined before. This work presents the synthesis of four widely used cinchona-based organocatalyst classes (hydroxy, amino, squaramide, and thiourea) with different saturation on the quinuclidine unit (ethyl, vinyl, ethynyl) started from quinine, the most easily available cinchona derivative. Big differences were found in basicity of the quinuclidine unit by measuring the pKa values of twelve catalysts in six solvents. The effect of differences was examined by testing the catalysts in Michael addition reaction of pentane-2,4-dione to trans-β-nitrostyrene. The 1.6–1.7 pKa deviation in basicity of the quinuclidine unit did not result in significant differences in yields and enantiomeric excesses. Quantum chemical calculations confirmed that the ethyl, ethynyl, and vinyl substituents affect the acid-base properties of the cinchona-thiourea catalysts only slightly, and the most active neutral thione forms are the most stable tautomers in all cases. Due to the fact that cinchonas with differently saturated quinuclidine substituents have similar catalytic activity in asymmetric Michael addition application of quinine-based catalysts is recommended. Its vinyl group allows further modifications, for instance, recycling the catalyst by immobilization.

Synthesis and Properties of Poly(1-trimethylsilyl-1-propyne) Containing Quaternary Ammonium Salts with Methyl and Ethyl Substituents

Poly(1-trimethylsilyl-1-propyne) modified with quaternary ammonium salts is synthesized. The introduction of salts into the polymer structure is carried out using a two-step method consisting in the bromination of the starting polymer followed by the addition of tertiary alkylamines—trimethylamine and triethylamine. The presence of ammonium salts is confirmed by the data of organometallic analysis and IR spectroscopy. X-ray diffraction analysis is used to study the supramolecular structure of the materials obtained. The TGA data indicate their high thermal and thermo-oxidative stability. The permeability, solubility, and diffusion coefficients of the poly(1-trimethylsilyl-1-propyne) samples containing trimethylamine and triethylamine salts for individual CO2, N2, and CH4 gases are determined. An increased ideal selectivity for the separation of gas pairs CO2/N2 and CO2/CH4 in modified poly(1-trimethylsilyl-1-propyne) is achieved owing to the increased selectivity of the dissolution of CO2 in quaternary ammonium salts.

Reducing the Pore Size of Covalent Organic Frameworks in Thin-Film Composite Membranes Enhances Solute Rejection

Three imine-linked covalent organic framework (COF) films are incorporated as active layers into separate thin-film composite (TFC) membranes and tested for their ability to reject an organic pollutant surrogate and salt from water. The synthesized membranes consist of a polyacrylonitrile (PAN) support and a TAPB-PDA-H, TAPB-PDA-Me, or TAPB-PDA-Et COF thin film. The latter two COFs direct six methyl and ethyl substituents per tiled hexagon into the pores, respectively, while maintaining the same topology across the series. These substituents decrease the effective pore size of the COF compared to the parent TAPB-PDA-H COF. The TFC TAPB-PDA-Me membrane rejects Rhodamine-WT (R-WT) dye and NaCl better than the TFC TAPB-PDA-H membrane, and the TFC TAPB-PDA-Et membrane exhibits the best rejection overall. The solution-diffusion model used to analyze this permeation behavior indicates that there is a systematic difference in rejection as subsequent pendant groups are added to the interior of the COF pores. These findings demonstrate the concept of tuning the selectivity of COF membranes by systematically reducing the effective pore size within a given topology.