Solution properties and mesophase formation of 4‐phenyl‐benzoylcellulose

Cellulose samples were derivatized in dimethylacetamide/LiCl (DMAc/LiCl) to give 4phenylbenzoylcelluloses (PBCs). The process is quantitative and leads to an highly substituted product, as verified by elemental analysis, IR and ¹³CNMR spectroscopy. PBC samples were characterized by viscometric and light scattering measurements in DMAc. The persistance length q is used to evaluate the theoretical critical volume fraction for mesophase formation (v _th, which has been found higher than the experimental critical one (v _exp)     

Synthesis and mesophase behaviour of rigid rod‐like phenylthiophene‐based amphiphilic diol derivatives

Novel amphiphilic block molecules consisting of a rigid 2‐phenylthiophene or 5‐phenylbithienyl core, with a polar glycerol group attached to the phenyl ring and one or two alkyl chains attached to the thiophene ring on the other side, have been synthesised by using Ni(0) and Pd(0) catalyzed coupling reactions as key steps. The thermotropic and solvent‐induced liquid crystalline behaviour of these compounds was investigated by polarising optical microscopy and X‐ray diffraction. The influence of the length, number and position of the alkyl chains, and the length of the rigid core, on their mesophase behaviour was investigated. Compounds with one alkyl chain in the terminal 5‐position on the thiophene ring form only smectic A phases, compounds with two adjacent alkyl chains attached in the 4‐ and 5‐positions of the thiophene ring exhibit thermotropic columnar mesophases, and those with two long alkyl chains attached to the 3‐ and 5‐positions form columnar LC phases only in the presence of water. Another compound containing the longer 5‐phenylbithienyl core unit and two alkyl chains attached in lateral positions to each of the thiophene rings is not mesogenic.     

Molecular dynamic study of the mechanism of formation of 2D carbon nanostructures in a solid Al–C nanocomposite grain

The behavior of graphene fragments in the structural fcc grains of aluminum was studied by molecular dynamics. In the course of structural relaxation, the graphene sheets united, twisted, and shifted toward the grain boundaries. The structure of the formed nanocomposite grain was studied in detail by statistical geometry. The distributions of Voronoi polyhedra according to the number of faces and of faces according to the number of sides were determined, including those after elimination of small-scale thermal fluctuations from the model. The angular distributions of the nearest geometrical neighbors were calculated, and the selfdiffusion coefficients were determined.     

Computational study on the mechanism of N-phenylimine derivatives’ pyrolysis reaction in the gas phase

In this work, quantum chemistry and kinetics calculations have been performed on the retro-cheletropic ene reactions of N-phenyl-1-methyl-6-methylenecyclohexa-2,4-dienylmethanimine (R1) and N-phenyl-2,2-dimethylbut-3-en (R2). Two major possible mechanisms have been considered and rate constants have been calculated using the transition state theory. The simple Wigner, Eckart zero-curvature tunneling and small-curvature tunneling (SCT) methods were evaluated. The best agreement with experimental rate coefficients was found when SCT correction was applied. A mean deviation of a factor 3 on the rate coefficients is found for the studied reactions at the temperatures of 417 and 773 K. Calculated rate coefficients showed that the tunneling corrections played a critical role in obtaining accurate rate coefficients, especially at lower temperature (417 K). Calculated rate coefficients are in good agreement with the reported experimental data and similar compounds in the case of R1 and R2, respectively. These results support the concerted and stepwise paths for the gas phase reactions of R1 and R2, respectively. Computed kinetic parameters confirmed that R1 had greater reactivity than R2. This trend explains the effects of an extra phenyl-like system on the stability of the transition state and hence increases the R1 rate constant. Calculated rate constants especially at the M06 level are in better agreement with the experimental values than the B3LYP ones. Natural bond orbital (NBO) studies of the reactants and their transition states reveal that their electron delocalization change is an important factor in the determination of the reactivity order for these compounds. Finally, the nature of bond making and breaking during the reactions has been investigated using the concepts of electron charge density and Laplacian in atom in the molecule method.     

Computational study on the encapsulation of ethylparaben into β-cyclodextrin

Two models namely A and B were considered to investigate the inclusion process of ethylparaben into β-CD cavity by means PM3, HF/6-31G (d) and B3LYP/6-31G (d). The obtained results with PM3 method clearly indicate that the formed complexes are energetically favored with or without solvent; the B complex is found more favored than A complex. The calculated deformations energies show that the geometry of β-CD is deformed in the complexation process on the other hand the ethylparaben do not undergo deformation. Finally, From NBO analysis, the donor and acceptor interactions between ethylparaben and β-CD were analyzed and discussed.     

Computational study of the heterodimerization between μ and δ receptors

A growing body of evidence indicated that the G protein coupled receptors exist as homo- or hetero-dimers in the living cell. The heterodimerization between μ and δ opioid receptors has attracted researchers’ particular interests, it is reported to display novel pharmacological and signalling regulation properties. In this study, we construct the full-length 3D-model of μ and δ opioid receptors using the homology modelling method. Threading program was used to predict the possible templates for the N- and C-terminus domains. Then, a 30 ns molecular dynamics simulations was performed with each receptor embedded in an explicit membrane-water environment to refine and explore the conformational space. Based on the structures extracted from the molecular dynamics, the likely interface of μ–δ heterodimer was investigated through the analysis of protein–protein docking, cluster, shape complementary and interaction energy. The computational modelling works revealed that the most likely interface of heterodimer was formed between the transmembrane1,7 (TM1,7) domains of μ receptor and the TM(4,5) domains of δ receptor, with emphasis on μ-TM1 and δ-TM4, the next likely interface was μ(TM6,7)-δ(TM4,5), with emphasis on μ-TM6 and δ-TM4. Our results were consistent with previous reports. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Vibrational study of the contact ion pair formation in the NaClO3–DMF system

Infrared and Raman studies of sodium chlorate in N,N-dimethylformamide (DMF) at different concentrations allowed to observe changes that are interpreted in terms of the contact ion pair formation. As the DMF is an ionising solvent it was possible to observe the equilibrium between associated and non-associated chlorate. In addition, depolarisation measurements were used to distinguish between the asymmetric and symmetric band representations in almost all regions of this anion. The vibrational assignment is entirely satisfactory indicating that in the Na⁺ClO₃⁻ contact ion pair the local symmetry around ClO₃⁻ changes from C_3v to C_S. In addition, our results do not show any evidence for the formation of solvent separated ion pairs and aggregates in this system.     

Recent advances in the application of nanoparticles in the selective reduction of carbon–carbon double bonds

Herein, we present recent advances in the application of metal nanoparticles in the selective hydrogenation of C–C double bonds. The review focuses on reduction methods of alkenes, arenes, and aromatic heterocycles, which were classified according to transition metals used as catalysts. The majority of described systems concern direct hydrogenation, which is of particular importance to industrial processes. Nonetheless, interesting transfer hydrogenation protocols were also developed, which may be incredibly convenient for laboratory purposes. Some of the methods are distinguished with excellent chemoselectivity making them the perfect tool for the synthesis of compounds containing reducible functional groups. Apart from noble metals, the application of earth-abundant ones as catalysts was a subject of studies, and the related methods were highlighted.     

2,5‐Dibromopyridine as a key building block in the synthesis of 2,5‐disubstituted pyridine‐based liquid crystals

Fifteen 2,5‐disubstituted pyridine based liquid crystals were synthesized exploiting the different reactivities of the bromine atoms in 2,5‐dibromopyridine under Negishi coupling conditions. Convenient approaches to both 2‐iodo‐5‐alkyl‐pyridines and 2‐alkyl‐5‐bromopyridines were also developed. The liquid crystalline behaviour of the synthesized materials was investigated using DSC and polarizing microscopy. The charge mobility of 2‐(4‐heptyloxyphenyl)‐5‐heptylpyridine was measured using the time of flight technique.     

Adsorption and DSC study of mineral–carbon sorbents obtained from coal tar pitch–polymer compositions

The purpose of this study was to determine the possibility of producing hydrophobic mesoporous mineral–carbon sorbents from aluminum hydroxide and compositions of coal tar pitch–polymers on carbonization at 600 °C in a nitrogen atmosphere. Blends of the products of co-precipitation of aluminum hydroxide in the carbonaceous substances medium were subjected to carbonization process. The extent of porous structure development was evaluated using low temperature nitrogen adsorption, adsorption of benzene vapors, and adsorption of iodine from aqueous solution. The highest value of BET surface area of about 370 m²/g was achieved for the carbonization product obtained from co-precipitated raw components with 10 wt% compositions coal tar pitch–polymer. These materials demonstrated high capacity to reduce organic pollutions from sewage. Pitch–polymer composition containing poly(ethylene terephthalate) or phenol–formaldehyde resin was studied by the means of DSC method in order to determine the high-temperature transformations taking place under the conditions of carbonization. DSC method enables to determine i.a. the decomposition temperatures of carbonizates produced from pitch–polymer compositions and the evaluation of their sorption abilities. The additive of poly(ethylene terephthalate) and phenol–formaldehyde resin caused the increase of thermal resistance of the pitch expressed by higher decomposition temperatures.     

Effect of γ-ray radiation on the polyacrylonitrile based carbon fibers

To investigate the effect of γ-ray radiation on the microstructural and mechanical properties of carbon fibers, carbon fibers were irradiated by ⁶⁰Co source. The interlayer spacing d₀₀₂ of carbon fibers decreased after irradiation. The Young’s modulus and density of the fibers increased with increasing dose. The tensile strength of fibers was found to increase at low dose and decrease at high dose. Additionally, Compton scattering effect caused by γ-ray is proposed to be responsible for the structural and mechanical changes of fibers. The results indicated that γ-ray irradiation was an effective method for improving the mechanical properties and graphitization degree of polyacrylonitrile based carbon fibers.     

A new class of bent‐shaped mesogens exhibiting unusual mesophase behaviour

Examples of a new class of bent‐core compounds are presented, the central fragment of which consists of a benzoyl derivative of a secondary cyclic amine. The mesophase behaviour has been studied by differential scanning calorimetry, polarizing optical microscopy, X‐ray diffraction and electro‐optical measurements. It was found that the five‐ring compounds form smectic CP or B₁ phases which are typical for bent‐core mesogens. The six‐ring compounds exhibit, in some cases, only conventional non‐polar smectic phases; in other cases non‐polar smectic phases as well as banana phases are seen. Of particular interest is the occurrence of a switchable uniaxial semectic A‐like phase with an antiferroelectric structure.     

Novel carboncarbon bond formation induced by depalladation of organometallic compounds

Two internal alkynes undergo insertion at 20°C into the PdC bond of the cyclopalladated derivative of dimethylaminomethylferrocene to give new organometallic compounds. When the reaction with diphenylacetylene is performed at higher temperatures, depalladation occurs readily to give six- and seven-membered ortho-fused rings through new annulation reactions of phenyl groups, formation of one of these involving also the cleavage of a CN bond.     

Kinetic study for the formation of microcrystalline “disks” of204T1I in gelatin medium

This paper presents a radiochemical study of the appearance of²⁰⁴T1I microcrystals and their development as disks resembling Liesegang rings, in gelatin, under different experimental conditions. Thus, kinetic diagrams have been traced, from which gel diffusion rate constants for radioactive ions were calculated, as well as reaction rate constants between reactant species:²⁰⁴T1⁺ and I^–, in colloidal medium, followed by the development of concentrated microcrystals under form of one or more disks. There is an interconnection between gelatin concentration of the colloidal medium, on one hand, and²⁰⁴T1I microcrystal disks number and dimensions, on the other hand, disks which appeared in gel as a result of the global process of nucleation.     

Computational approaches in the design of synthetic receptors – A review

The rational design of molecularly imprinted polymers (MIPs) has been a major contributor to their reputation as “plastic antibodies” – high affinity robust synthetic receptors which can be optimally designed, and produced for a much reduced cost than their biological equivalents. Computational design has become a routine procedure in the production of MIPs, and has led to major advances in functional monomer screening, selection of cross-linker and solvent, optimisation of monomer(s)-template ratio and selectivity analysis. In this review the various computational methods will be discussed with reference to all the published relevant literature since the end of 2013, with each article described by the target molecule, the computational approach applied (whether molecular mechanics/molecular dynamics, semi-empirical quantum mechanics, ab initio quantum mechanics (Hartree-Fock, Møller–Plesset, etc.) or DFT) and the purpose for which they were used. Detailed analysis is given to novel techniques including analysis of polymer binding sites, the use of novel screening programs and simulations of MIP polymerisation reaction. The further advances in molecular modelling and computational design of synthetic receptors in particular will have serious impact on the future of nanotechnology and biotechnology, permitting the further translation of MIPs into the realms of analytics and medical technology.     

Recent advances in the development of electrochemical hydrogen peroxide carbon nanotube–based (bio)sensors

The relevance of H₂O₂ as biomarker for different neurodegenerative diseases and cancer has been one of the most significant incentives for the development of new (bio)sensors that allow a more sensitive, selective, fast, and stable quantification of H₂O₂. In this regard, the association of carbon nanotubes with hemoproteins, nanoparticles, and other nanostructures and different electrochemical transducers has offered new avenues for the construction of innovative H₂O₂ bioanalytical platforms. This short review highlights the most relevant contributions in the field of electrochemical (bio)sensors for H₂O₂ based on carbon nanotubes published in the period 2016–2018.     

A systematic study on the influence of carbon on the behavior of hard-to-ionize elements in inductively coupled plasma–mass spectrometry

A systematic study on the influence of carbon on the signal of a large number of hard-to-ionize elements (i.e. B, Be, P, S, Zn, As, Se, Pd, Cd, Sb, I, Te, Os, Ir, Pt, Au, and Hg) in inductively coupled plasma–mass spectrometry has been carried out. To this end, carbon matrix effects have been evaluated considering different plasma parameters (i.e. nebulizer gas flow rate, r.f. power and sample uptake rate), sample introduction systems, concentration and type of carbon matrix (i.e. glycerol, citric acid, potassium citrate and ammonium carbonate) and type of mass spectrometer (i.e. quadrupole filter vs. double-focusing sector field mass spectrometer). Experimental results show that P, As, Se, Sb, Te, I, Au and Hg sensitivities are always higher for carbon-containing solutions than those obtained without carbon. The other hard-to-ionize elements (Be, B, S, Zn, Pd, Cd, Os, Ir and Pt) show no matrix effect, signal enhancement or signal suppression depending on the experimental conditions selected. The matrix effects caused by the presence of carbon are explained by changes in the plasma characteristics and the corresponding changes in ion distribution in the plasma (as reflected in the signal behavior plot, i.e. the signal intensity as a function of the nebulizer gas flow rate). However, the matrix effects for P, As, Se, Sb, Te, I, Au and Hg are also related to an increase in analyte ion population caused as a result of charge transfer reactions involving carbon-containing charged species in the plasma. The predominant specie is C⁺, but other species such as CO⁺, CO₂⁺, C₂⁺ and ArC⁺ could also play a role. Theoretical data suggest that B, Be, S, Pd, Cd, Os, Ir and Pt could also be involved in carbon based charge transfer reactions, but no experimental evidence substantiating this view has been found.     

Theoretical study of formation mechanism for 4-methyl-3-phenylbenzonitrile in the course of the Hiyama and Suzuki–Miyaura reactions

A theoretical study on the mechanism of conversion of 3-bromo-4-methylbenzonitrile into 4-methyl-3-phenylbenzo-nitrile in the course of the Suzuki–Miyaura and Hiyama−Denmark cross-coupling reactions has been performed at Cam-B3LYP-D3 level of theory. With the use of Pd–NHC type complex as the catalyst, the Hiyama−Denmark cross-coupling is best suited for this process from both thermodynamic and kinetic aspects.     

Ring-opening of cyclic ethers with carbon–carbon bond formation by Grignard reagents

The ring-opening of cyclic ethers with concomitant C–C bond formation was studied with a number of Grignard reagents. The transformation was performed in a sealed vial by heating to ∼160 °C in an aluminum block or at 180 °C in a microwave oven. Good yields of the product alcohols were obtained with allyl- and benzylmagnesium halides when the ether was tetrahydrofuran or 3,3-dimethyloxetane. Lower yields were obtained with substituted tetrahydrofurans while no ring-opening was observed with tetrahydropyran. Only highly reactive allyl and benzyl Grignard reagents participated in the transformation while no reaction occurred with other alkylmagnesium halides.     

Porous structure and thermal properties of carbon adsorbents from pitch–polymer compositions

The study results of porous structure and thermal properties of carbon adsorbents (AC) obtained from pitch–polymer compositions were presented. The compositions were carbonized and activated with steam, potassium hydroxide, and magnesium and potassium carbonates. For the obtained AC, the thermal analysis and the determination of adsorption value of iodine and porous structure by adsorption/desorption of nitrogen at 77 K were carried out. The possibility of obtained activated carbons from pitch–polymer compositions was demonstrated. The use of untypical feedstock, as an effect of combination of bituminous substance with polymeric waste and improvement of the methods of production, creates the potential possibility to produce carbon adsorbents of interesting properties and porous structure.