DMT [(−)-(2<Emphasis Type="Italic">R</Emphasis>,3<Emphasis Type="Italic">R</Emphasis>)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol], a highly efficient host compound for nitroaromatic guests: selectivity,X-ray and thermal analyses

In this work, we reveal that the compound (?)-(2R,3R)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) is a highly efficient host material for nitroaromatics o-nitrotoluene (o-NT), m-nitrotoluene (m-NT), p-nitrotoluene (p-NT) and nitrobenzene (NB). Each of these guests was included with a 2:1 host:guest ratio. The host displayed selectivity for p-NT and NB when these guests were mixed in equimolar proportions with any one of the other guest solvents, and the host recrystallized from this binary mixture. A selectivity order for the host in these conditions was thus noted to be NB?≈?p-NT?>?o-NT?>?m-NT. Furthermore, guests were also mixed in non-equimolar proportions and the host behaviour analysed, the results of which were in accordance with observations from the equimolar studies. Additionally, an equimolar quaternary experiment of all four guests provided a somewhat adjusted host selectivity order [p-NT (39.9%)?>?NB (30.2%)?>?m-NT (17.1%)?>?o-NT (12.8%)]. Single crystal diffraction analyses of all four complexes showed the crystals to share the same host packing, and comparable host–guest interactions were observed in each. However, thermal analyses, both DSC and TG, showed that the preferred guests p-NT and NB formed complexes with increased relative thermal stabilities, and this observation correlated with the selective behaviour of the host in competition experiments.     

Synthesis of 6,8-substituted 4-(hydroxyphenylamino)- and 4-(aminophenylamino)-2-methylquinolines

A procedure has been developed for the synthesis of 4-(hydroxyphenylamino)- and 4-(aminophenylamino)-2-methylquinolines having a substituent in the 6(8)-position of the quinoline ring from the corresponding 4-chloro-2-methylquinolines and o-, m-, and p-aminophenols and o-, m-, and p-phenylenediamines.     

Compounds of the menthane series. Synthesis of unsaturated primary alcohols with the <Emphasis Type="Italic">o</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-menthane skeletons

Precursors to terpene alcohols of the o- and p-menthane series (o-cimen-7-ol and o- and p-cimen-9-ols) were synthesized, and their reduction with lithium in ethylenediamine was studied. The reduction of o- and p-cimen-9-ols in the presence of isopropyl alcohol selectively afforded the corresponding 1,4-dihydro derivatives. Under analogous conditions, o-cimen-7-ol was converted into a mixture of unsaturated hydrocarbons. The reduction with lithium in ethylenediamine in the absence of isopropyl alcohol in all cases gave mixtures of menthene alcohols.     

Synthesis and some transformations of polybrominated quinone diazides

The reduction of polybrominated o- and p-nitrophenols with granular tin in concentrated aqueous HCl gave polybrominated aminophenols which were diazotized with sodium nitrite in concentrated sulfuric acid at 0°C to obtain polybrominated o- and p-quinone diazides. Their thermolysis with elimination of nitrogen generated ketocarbenes which reacted with acetylacetone to form insertion products at the activated methylene group. Ketocarbenes generated from o-quinone diazides reacted with typical dipolarophiles such as acetonitrile, benzonitrile, styrene, and phenylacetylene to afford the corresponding [3 + 2]-cycloaddition products.     

Formation of solvate structures by the <Emphasis Type="Italic">ortho</Emphasis>-, <Emphasis Type="Italic">meta</Emphasis>-, and <Emphasis Type="Italic">para</Emphasis>-isomers of hydroxybenzoic acid in supercritical fluid

The solvate structures formed by the ortho-, meta-, and para-isomers of hydroxybenzoic acid (o-HBA, m-HBA, and p-HBA) with a polar co-solvent (methanol at a concentration of 0.030 and 0.035 mole fractions) in supercritical carbon dioxide at a constant density of 0.7 g/cm³ and temperatures of 318 and 328 K have been studied by the classic molecular dynamics. It has been determined that a stable hydrogen-bonded complex with the co-solvent forms via the hydrogen of the carboxyl group for all isomers. The probability of this complex existence is high at all temperatures and concentrations. In the o-HBA molecule, the other functional groups are engaged in the intramolecular hydrogen bond, but not involved in interactions with methanol. It has been found that m-HBA and p-HBA can be involved in hydrogen bonds with methanol via hydroxyl hydrogen and oxygen atoms; they are characterized by the presence of one more co-solvent molecule (rarely, two molecules) in their solvation shell and intermittent formations/breakages of hydrogen bonds via other functional groups. These bonds are far less stable, and their formation is sensitive to change of temperature and co-solvent concentration. It has been concluded that the degree of selective solvation of m-HBA and p-HBA by co-solvent molecules is approximately the same, but the rate of structural rearrangements in the nearest environment of m-HBA is higher than that of p-HBA.     

Determination of migrated phthalic acid residues into edible oils using a green mode of air-assisted liquid–liquid microextraction followed by high-performance liquid chromatography–diode array detector

In this study, for the first time, an organic solvent-free air-assisted liquid–liquid microextraction method has been reported for the extraction and preconcentration of phthalic acids (o-phthalic acid, m-phthalic acid, and p-phthalic acid) from edible oil samples. The method is based on the repeated aspirating/injection of an alkaline aqueous solution and the oil sample mixture in a conical bottom centrifuge tube to form a cloudy solution. After phase separation by centrifuging, the sedimented phase is directly analyzed by high-performance liquid chromatography–diode array detection. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.11–0.29 and 0.28–0.91 ng mL^?1, respectively. Extraction recoveries and enrichment factors were from 81 to 97% and 406 to 489, respectively. The relative standard deviations for the analysis of 5 ng mL^?1 of each analyte were less than 5.9% for intraday (n = 6) and interday (n = 5) precisions. Finally, different oil samples were successfully analyzed using the proposed method and m-phthalic acid, and p-phthalic acid were determined in some of them at ng mL^?1 level.     

Fast Determination of Monocyclic Aromatic Hydrocarbons in Ambient Air Using a Portable Gas Chromatography–Photoionization Detector

Many air sampling methods are time consuming and require complex pre-treatment steps. Gas chromatography–photoionization detector (GC–PID) is a rapid method for sampling and analysis. However, although it has been used in a number of studies, its operating conditions and performance parameters have not been optimized systematically. In this study, a GC–PID method for analysis of monocyclic aromatic hydrocarbons in gas samples without pre-concentration or enrichment was developed and optimized. This GC–PID can perform both online and off-line analysis. In online analysis, the sample was pumped directly into a Teflon sample loop (pumped online injection), which resulted in minimal loss of sample. The optimum parameters were as follows: 30-s pumping time, 10 mL min^?1 of carrier gas flow rate, and 40 °C oven temperature. GC–PID was applied to analysis of benzene, toluene and xylene. The calibration curves showed good linearity for online analysis. The results obtained by GC–PID were accurate and reliable, with all the correlation coefficients ≥0.9972 and all the relative standard deviations <3%. A mixture of benzene, toluene, and o-, m-, and p-xylenes was separated satisfactorily in 10 min, except for m- and p-xylene. The performance of the portable GC–PID was compared with that of an ATD–GC–FID for quantification of benzene, toluene and xylene in calibration gas samples, and benzene, toluene, ethylbenzene, and the o-, m-, and p-xylenes in outdoor ambient air. The results indicated that GC–PID with pumped online injection was stable and accurate for analysis of these monocyclic aromatic hydrocarbons.     

Interaction of positional isomers of dimethylbenzene with graphite

The optimized geometries and interaction energies of the intermolecular heterodimers of coronene with o-, m-, and p-dimethylbenzenes (xylenes) calculated by DFT in the PBE0 and B97D functionals were compared. The applicability of coronene as a model for qualitative assessment of the interaction of mononuclear aromatic compounds with the graphite surface was demonstrated. The necessity of including long-range dispersion interactions in DFT calculations of the dimerization energies of aromatic systems was shown. The sorption enthalpies of p- and m-xylenes were shown to be almost equal irrespective of the conditions of the chromatographic experiment. The preferred sorption of p- over m-xylene on graphite is solely due to the entropy factor.     

The thermodynamic properties of the [(Me<Subscript>3</Subscript>Si)<Subscript>7</Subscript>C<Subscript>60</Subscript>]<Subscript>2</Subscript> fullerene complex

The temperature dependence of the heat capacity C _p ^o of the [(Me₃Si)₇C₆₀]₂ fullerene complex was measured for the first time using precision adiabatic vacuum calorimetry over the temperature range 6.7–340 K and high-accuracy differential scanning calorimetry at 320–635 K. For the most part, the error in the C _p ^o values was about ±0.5%. An irreversible endothermic effect caused by the splitting of the dimeric bond between fullerene fragments and the thermal decomposition of the complex was observed at 448–570 K. The thermodynamic characteristics of this transformation were calculated and analyzed. Multifractal analysis of the low-temperature (T < 50 K) heat capacity was performed, and conclusions were drawn concerning the character of the heterodynamicity of the structure. The experimental data obtained were used to calculate the standard thermodynamic functions C _p ^o (T), H ^o (T) ? H ^o (0), S ^o (T) ? S ^o (0), and G ^o (T) ? H ^o (0) over the temperature range from T → 0 to 445 K and estimate the standard entropy of formation of the compound from simple substances at 298.15 K. The standard thermodynamic properties of [(Me₃Si)₇C₆₀]₂ are compared with those of the (C₆₀)₂ dimer, the [(η⁶-Ph₂)₂Cr]⁺[C₆₀]^?? fulleride, and the initial C₆₀ fullerene.     

Design of postmetallocene Schiff base-like catalytic systems for polymerization of olefins: XII. Synthesis of tetradentate bis-salicylaldehyde imine ligands

Reactions of salicylaldehyde, 3-tert-butylsalicylaldehyde, and 3,5-di-tert-butylsalicylaldehyde with 1,4-diaminobutane, 1,6-diaminohexane, 4,4′-diaminodiphenylmethane, 4,4′-diamino-3,3′,5,5′-tetramethyldiphenylmethane, 4,4′-diamino-5,5′-dicyclopentyl-3,3′-dimethyldiphenylmethane, 4,4′-diamino-5,5′-dicyclohexyl-3,3′-dimethyldiphenylmethane, bis(4-aminophenyl) sulfone, o,o′- and p,p′-diaminodiphenyl ethers, 1,4-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and 4,4″-diamino-p-terphenyl gave a series of the corresponding Schiff bases which can be used as tetradentate ligands for the synthesis of titanium and zirconium complexes.     

Synthesis,structure, and antibacterial properties of ternary rare-earth complexes with <Emphasis Type="Italic">o</Emphasis>-methylbenzoic Acid and 1,10-phenanthroline

Ternary rare-earth complexes with o-methylbenzoic acid (o-MBA) and 1,10-phenanthroline (Phen) Ln₂(o-MBA)₆(Phen)₂ · nH₂O(n = 0, 1) (Ln = La, Pr, Y, Yb) were synthesized and characterized by elemental analysis, IR, X-ray diffraction, and TG-DTG means. The complex La₂(o-MBA)₆(Phen)₂ · H₂O (I) is composed of two species of binuclear molecules in which the La³⁺ ion is coordinated with two nitrogen atoms of Phen and seven oxygen atoms of carboxylate groups. The carboxylate groups were bonded to La³⁺ in three modes: chelating-bidentate, bridging-bidentate, and chelating-bridging tridentate. The La³⁺ ion adopted a vigorous distorted monocapped square antiprism geometry. Complex I belongs to the triclinic crystal system, P space group, lattice parameters: a = 13.058(3), b = 12.7584(11), c = 20.773(4) Å, α = 101.18(3)°, β = 93.88(3)°, γ = 115.82(3)°, V = 3283.0(11)ų, Z = 2, ρ_calcd = 1.484 mg/m³, M _r = 1467.06, F(000) = 1476, μ = 1.350 mm^-1. The structure was refined to R _l = 0.0631 and wR ₂ = 0.1504. The antibacterial activity test indicates that these complexes exhibit better antibacterial ability against Escherichia coli and Staphylococcus aureus than the corresponding rare-earth chloride or o-MBA.     

Stereochemistry of seven-membered heterocycles: XLVI. Synthesis and dynamic <Superscript>13</Superscript>C NMR spectroscopy of spiro[cyclohexane-1,4′-[3,5]dioxabicyclo[5.1.0]octanes]. DFT calculations of structurally related formaldehyde and acetone acetals

Spiro[cyclohexane-1,4′-[3,5]dioxabicyclo[5.1.0]octanes] were synthesized, and their conformational behavior was studied by dynamic ¹³C NMR spectroscopy. Anancomeric displacement of conformational equilibrium toward two nonequivalent twist conformers with close energies was revealed. The relative Gibbs energies ΔG ^o and enthalpies of formation ΔH ^o of twist and chair-like conformers with endo and exo orientation of the three-membered ring of structurally related formaldehyde and acetone acetals were calculated in terms of the density functional theory at the B3LYP/6-31G(d,p) level. Like spiro-cyclohexane analogs, they were shown to have a non-chair conformation.     

Structure and Reactivity of Bicyclo[2.2.1]hept-2-ene-<Emphasis Type="Italic">endo</Emphasis>-5,<Emphasis Type="Italic">endo</Emphasis>-6-dicarboxylic (endic) Acid Hydrazide

Establishing of the structure of hydrazinolysis product obtained from bicyclo[2.2.1]hept-2-ene-endo-5, endo-6-dicarboxylic (endic) acid was performed by preparation of the compound under alternative conditions followed by comparison of the characteristics and spectral parameters of the resulting substances, and also by quantum-chemical calculations by the density functional method of the chemical shifts in ¹H and ¹³C NMR spectra of different reaction products. The X-ray diffraction analysis of the hydrazide was also carried out. The compound obtained was assigned a structure of N-aminobicyclo[2.2.1] hept-2-ene-endo-5,endo-6-dicarboximide. The products were prepared by its reactions with arylsulfonyl chlorides, benzoyl chlorides, m-tolyl and p-toluene-sulfonyl isocyanates, phenyl isothiocyanate, with o-nitrobenzaldehyde, and oxiranes (1,2-epoxycyclohexane and 2,3-epoxypropylcarbazole). The aromatic sulfonamides, carboxamides, and ureas were epoxidized by performic acid obtained in situ from the formic acid and hydrogen peroxide. Products of [3+2]-cycloaddition of aryl azides to the strained double bond in the N-aminobicyclo[2.2.1] hept-2-ene-endo-5,endo-6-dicarboximide and its derivatives. The structures of compounds obtained were confirmed by their IR, 1H and 13C NMR spectra.     

Preparation and characterization of the inclusion complexes of equol with sulfobutylether-β-cyclodextrin: their antioxidant activity and dissolution evaluation

The formation of inclusion complexes between S-(?)-equol (SEq) and cyclodextrins (CDs) was investigated. The binding constant (K_c) of the SEq/sulfobutylether-β-cyclodextrin (SBE-β-CD) inclusion complex was determined to be 1600 L/mol based on UV data. The phenyl ring of the SEq molecule was found to be inserted from the secondary hydroxyl face of the SBE-β-CD as evidenced from ¹H–¹H rotating frame nuclear Overhauser effect spectroscopy (ROESY) NMR. The thermal properties of the solid SEq/SBE-β-CD inclusion complexes prepared by physical mixing, kneading and freeze-drying methods were studied by differential scanning calorimetry. For the solid complex obtained by the freeze-drying method, the endothermic peak corresponding to the melting point of SEq disappeared. The solid SEq/SBE-β-CD complexes exhibited a high score in antioxidant activity evaluation tests compared to SEq alone. Dissolution test revealed that the solid complex obtained by freeze-drying method had improved dissolution of SEq.     

Synthesis and structure of 1-(buta-1,3-dien-2-yl)pyrazoles and their behavior in Diels-Alder reactions

A convenient procedure has been developed for the synthesis of cis-and trans-isomeric 1-(buta-1,3-dien-1-yl)-1H-pyrazoles by reaction of the corresponding pyrazoles with β-methylacrolein diethyl acetal and subsequent 1,4-cleavage of the nucleophilic substitution products. The behavior of the title compounds in Diels-Alder reactions with maleic anhydride has been studied. According to the ¹H NMR data, 1-(buta-1,3-dien-1-yl)-1H-pyrazole is a mixture of cis and trans isomers. Butadienylpyrazoles having methyl groups in the pyrazole ring do not react with maleic anhydride.     

Reduction of nitrophenols in an electrocatalytic system

Results of research into hydrogenation of o- and p-nitrophenols in an electrocatalytic system on a cathode activated with d- and s-metal catalysts are presented. The optimal conditions for o-aminophenol formation on Raney nickel were identified by the probability-determined method for the experimental design.     

Copper,cobalt, and nickel complexes of azomethine compounds containing phenylazo group in the amine fragment: Syntheses,structures, and magnetic properties

The Cu, Ni, and Со complexes based on the following new azomethine compounds containing azobenzene groups in the ortho- or para-positions of the amine fragment are synthesized: 2-allyl-6-[(E)-[4-(E)-phenylazophenyl]iminomethyl]phenol (HL¹), 2-allyl-6-[(E)-[4-methyl-2-[(E)-phenylazo]-p-tolylazo] iminomethyl]phenol (HL²), 5-methoxy-2-[(E)-[4-[(E)-phenylazo]phenyl]iminoethyl]phenol (HL³), and 5-methoxy-2-[(E)-[4-methyl-2-[(E)-p-tolylazo]phenyl]iminomethyl]phenol (HL⁴). The structures of the complexes are determined by the data of IR and ¹Н NMR spectroscopy (for the azomethine compounds), X-ray absorption spectroscopy, and magnetochemistry. The coordination centers of all Cu complexes have a distorted square structure. A direct dependence of the geometry of the coordination polyhedron on the position of azobenzene groups in the amine fragments of the ligands is found for the Ni and Co complexes. The octahedral environment of the nickel and cobalt ions takes place in the case of the ortho-position of the amine fragment, whereas the square environment for the Ni complexes or the tetrahedral environment for the Co complexes is observed at the para-position. The molecular structures of two azomethines HL¹ and HL⁴ are determined by X-ray diffraction analysis (CIF files CCDC nos. 1552836 (HL¹) and 1552837 (HL⁴)).     

Hydrogenation of biphenyl and isomeric terphenyls over a Pt-containing catalyst

Catalytic hydrogenation of benzene, biphenyl, and ortho-, metha-, and para-isomers of terphenyl over a 3 wt.% Pt/C at 180 °C and 70 atm was studied. The directions of hydrogenation of each substrate were revealed. Relationships between structures of the substrate and hydrogen consumption rates were found. It was shown that hydrogenation rate decreases on going from benzene to terphenyl and with increasing degree of the substrate hydrogenation. Hydrogenation rate of terphenyl isomers decreases in the following order: p-terphenyl > > m-terphenyl > o-terphenyl.     

Electronic Structure and Relative Stabilities of 10- and 12-Vertex. <Emphasis Type="Italic">Closo</Emphasis>and <Emphasis Type="Italic">Nido</Emphasis>-Heteroborane Clusters of Ga,Ge, and As Elements

A DFT method with the B3LYP functional and the 6-311++G(d,p) diffuse basis set is used to predict geometries, relative stabilities, electronic structures, and the bonding of closo- and nido-Ga_mB_n–mH _n ^2? , Ge_mB_n–mH _n ^m?2 , and As_mB_n–mH _n ^{2 m?2} (n = 10, 12 and m = 1, 2) Clusters are obtained by replacing BH with isolobal GaH, GeH⁺, and AsH²⁺ fragments, keeping the same skeleton electron pairs (SEP). Based on the polyhedral skeletal electron pairs theory (PSEPT), closo and nido structures are predicted and can be of significant interest for experimentalists working in the field of heteroboranes. Different cluster stabilities are studied according to Gimarc′s and Williams′ rules, where our calculations show that the monosubstituted clusters deviate from these rules, giving rise to open structures. As₂B₈H _n ²⁺ as 10-vertex structures lead to nido-type clusters, however, Ge_mB_n–mH _n ^m?2 (n = 10, 12 and m = 1, 2) give rise to closo isomers with close energies. All optimized structures exhibit large HOMO–LUMO gaps suggesting a good kinetic stability, thus predicting their isolation and characterization.     

Electron density distribution in crystals of the antimony(V) spiroendoperoxide complexes

The experimental and theoretical electron densities in complexes [6-(2,6-di-iso-propylphenyl)imino-2,4-di-tert-butylcyclohexa-2,4-diene-1-peroxo-1-olato-N,O,O′]tris(p-chlorophenyl)antimony(V), (p-Cl–C₆H₄)₃Sb(2,6-iso-Pr–Ph–AP) · O₂ (I), and [6-(2,6-dimethylphenyl)imino-2,4-di-tert-butylcyclohexa-2,4-diene-1-peroxo-1-olato-N,O,O′]tris(p-chlorophenyl)antimony(V), (p-Cl–C₆H₄)₃Sb(2,6-Me–Ph–AP) · O₂ (II), where AP is 4,6-di-tert-butyl-N-o-iminobenzoquinone dianion, are studied on the basis of high-resolution X-ray diffraction data and theoretical calculations using the density functional theory (B3LYP/DGDZVP). The nature of chemical bonds and the charge distribution on atoms are studied, and the energy of molecular oxygen addition to the Sb(V) o-aminophenolate complexes is estimated. The structures are deposited with the Cambridge Crystallographic Data Centre (CIF files CCDC nos. 1560600 (spherical refinement) and 1560601 (multipole refinement) for complex I; 1560602 (spherical) and 1560603 (multipole) for complex II).