Volumetric properties of the (tetrahydrofuran + water) and (tetra-n-butyl ammonium bromide + water) systems: Experimental measurements and correlations

In this communication, we report experimental density data for the binary mixtures of (water + tetrahydrofuran) and (water + tetra-n-butyl ammonium bromide) at atmospheric pressure and various temperatures. The densities were measured using an Anton Paar™ digital vibrating-tube densimeter. For the (tetrahydrofuran + water) system, excess molar volumes have been calculated using the experimental densities and correlated using the Redlich–Kister equation. The Redlich–Kister equation parameters have been adjusted on experimental results. The partial molar volumes and partial excess molar volumes at infinite dilution have also been calculated for each component. A simple density equation was finally applied to correlate the measured density of the (tetra-n-butyl ammonium bromide + water) system.     

Investigation of the regioselectivity of alkylation of 3-nitropyridin-2(1H)-ones

Alkylation of 3-nitropyridin-2(1H)-ones in the presence of bases affords N-alkylated products and sometimes O-alkylated products. The yields and relative amounts of N- and O-alkylated products depend substantially on the size of the substituent at the C(6) atom of pyridone.     

Synthesis of (Z)-alkene-containing cis-proline dipeptide mimetics using samarium(II) diiodide (SmI2)-mediated reductive alkylation reaction

The amide bond between an amino acid and proline can take the trans- or cis-conformation. The conformation influences both the structure and function of peptides and proteins. Therefore, constrained mimetic, which corresponds to Pro-dipeptides whose amide bond is replaced with an (E)- or (Z)-alkene, is a useful bioprobe for elucidating the structure-function relationship of peptides and proteins. Herein, we report the synthesis of cis-(Z)-alkene-containing Pro-dipeptide mimetics via a samarium(II) diiodide (SmI₂)-mediated reductive alkylation reaction.     

Selective alkylation of xylenes by alcohols on zeolite catalysts

The peculiarities of catalytic performance of crystalline aluminosilicates of different types and compositions (X, Y including dealuminated Y, mordenite, pentasil ZSM-5), as well as of amorphous aluminosilicate catalyst in conversion of xylene + alcohol mixtures were studied. New data were obtained for alkylation ofo-xylene withtert-butyl alcohol, concerning controlling the selectivity and stability of the zeolite catalysts in reactions proceeding with the participation of water, including the water evolved during the reaction, in particular by controlling the acidic properties and hydrophobycity of the zeolites. A catalyst ensuring production of 1,2-dimethyl-4-tert-butylbenzene (DMTBB) with a 94% yield and selectivity of alcohol conversion to the target product of 94–97% was developed. The catalyst can be used as the basis for a high-performance and environmentally safe method for the synthesis of DMTBB. The catalysts developed can be also used for selective alkylation ofo-xylene by C₃-C₅ alcohols and for alkylation ofm-xylene bytert-butyl alcohol.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 12, pp, 2912–2917, December, 1996.     

The reactivity of N,N-dialkyl-N-(3-phenylsulfinyltetrahydrofuran-2-ylidene)ammonium bromide

trans-Stereoselective electrophilic cyclization of (2R*,SS*)-N, N-diisopropyl-2-phenylsulfinylpent-4-enamide under the action of bromine afforded (3R*,5S*, SS*)-N-(5-bromomethyl-3-phenylsulfinyltetrahydrofuran-2-ylidene)-N,N-diisopropylammonium bromide. Its transformations under the conditions of hydrolysis, dehydrobromination, and hydride reduction were studied. Dedicated to Academician V. A. Tartakovsky on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1485–1490, August, 2007.     

Palladium-catalyzed alkylation of 1,4-dienes by C-H activation

Activated: the title reaction proceeds with a broad range of nucleophiles and variously substituted 1,4-dienes under mild conditions, and provides direct access to the corresponding 1,3-diene-containing products with high regio- and stereocontrol (see scheme; 2,6-DMBQ=2,6-dimethylbenzoquinone, EWG=electron-withdrawing group). This is the first catalytic allylic C-H alkylation that proceeds in the absence of sulfoxide ligands.     

1H NMR spectroscopic study of theert-butyl chloride—aluminum bromide cationic initiating system

The interaction oftert-butyl chloride with aluminum bromide in methylene dibromide at −30°C leads to the formation of two types of adducts, which give signals with δ 2.4 and 3.2 in the¹H NMR spectra in addition to that of free alkyl halide. these signals are attributed to a polarized complex (PC) and ion pair (IP), respectively. An excess of AlBr₃ shifts the equilibria toward IP. The latter contains more AlBr₃ than the polarized complex. Based on the spectral data, we calculated the limiting values of some equilibrium constants. The ability of AlBr₃ to solvate counterions is consistent with the results of isobutylene polymerization under the action of the initiating Bu^tCl−AlBr₃ system at different ratios of the starting concentrations [AlBr₃]₀/[Bu^tCl]₀. An increase in this ratio results in both the acceleration of polymerization and an increase in the relative role of chain transfer reactions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2217–2222, November, 1998.     

Dynamic shear modulus in the splitting region of poly(alkyl methacrylates)

A systematic study of the dynamic shear modulusG ^*=G+G in three poly(alkyl methacrylates) (PEMA, PnPMA, PnBMA) at frequencies between 0.001 and 500 rad/s is presented. As the splitting frequencies _s are low, aging effects can be observed in the splitting region. There is a systematic shift of the splitting frequency _s to lower values with increasing length of the alkyl side group. In PnBMA a separate shear appearance is observed about two frequency decades below the local mode . This is discussed in terms of the concept of minimal cooperativity. Aging effects are: Shift of the maximum loss frequency to lower values, peak sharpening of the relaxation, and intensity changes of and . These effects are discussed in terms of the sequential aging concept. Aging leads to a pronounced bending of the traces upwards from the equilibrium line in the Arrhenius diagram. These non-equilibrium phenomena are promoted by the small slope m=d(log )/dT of the trace in the splitting region.Dedicated to Prof. E. W. Fischer at the occasion of his 65th Birthday Lieber Herr Fischer, die Hallenser Polymerphysiker danken Ihnen aufrichtig für die warmherzige und effektive Förderung der Polymerwissenschaften im Raum Halle-Merseburg.     

New Complexes of Nickel(II) Containing Macrocyclic Diaminodiiminepiperazine Ligands: Synthesis and Electrochemical Properties

Complexes of Ni(ClO₄)₂ with 1,4-bis(2-aminobenzyl)piperidine (1) and 1,4-bis(2-amino-4-tertbutyl)piperidine (2) and products of their cyclization with ortho-phthalic aldehyde in methanol [NiL3][ClO₄]₂ (3) and [NiL4][ClO₄]₂ (4), respectively, are synthesized. Complexes 1 and 2 can be reduced on a platinum electrode irreversibly. Cyclic complexes 3 and 4 undergo reduction reversibly or quasi-reversibly in two or three stages. The reduction products react with n-BuI or n–BuBr (Bu = butyl) via an inner-sphere mechanism of oxidative attachment, probably, with the formation of the Ni–C bond.     

Electrochemical synthesis and studies of substituted 2-thiopyridines

A series of substituted 2-alkyl(aryl-, hetaryl-)thiopyridines was prepared by cathodic electrolysis of thiols in the presence of 2-chloro-3-cyano-4-methoxymethyl-6-methylpyridine or 4-chloro-6-methyl-3-oxo-1H-furo[3,4-c]pyridine. The reaction of 3-cyano-4-methoxymethyl-6-methyl-2(1H)-thiopyridone with alkyl halides in the presence of KOH is regioselective and leads toS-alkyl derivatives. The advantages of electrosynthesis for the preparation of 2-alkylthiopyridines fused with 2(5H)-furanone and of 3-aminothieno [2,3-b]pyridines is demonstrated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2215–2219, December, 1994.     

Excess Enthalpies of Ternary Mixtures: (2-Methyltetrahydrofuran or Di-n-Butyl ether) + 3-Methylpentane + n-Decane at 25°C

Measurements of excess molar enthalpies at 25°C in a flow microcalorimeter are reported for the two ternary mixtures 2-methyltetrahydrofuran + 3-methylpentane + n-decane and di-n-butyl ether + 3-methylpentane + n-decane. Smooth representations of the results are described and used to construct constant-enthalpy contours on Roozeboom diagrams. It is shown that useful estimates of the ternary enthalpies can be obtained from the Liebermann–Fried model using only the physical properties of the components and their binary mixtures.     

Effects of H/D-isotope substitution and temperature on the volume characteristics of tetra-n-butylammonium bromide dissolved in methanol and its D-isotopomers

Densities of Buⁿ ₄NBr solutions in MeOH, MeOD, and CD₃OH were measured at salt concentrations of up to 1.5 solvomolality units (nearly 2.63·10^–2 mole fraction) at 278.15, 288.15, 298.15, 308.15, and 318.15 K. The limiting partial molar volumes of Buⁿ ₄NBr dissolved in these alcohols were calculated. The isotope effects in the volume characteristics of the stoichiometric mixture of ions, [Buⁿ ₄N⁺ + Br^–], are mainly due to the vibrational changes in the solvent structure upon deuteration of different molecular fragments. Structural transformations in infinitely dilute solution of Buⁿ ₄NBr in methanol are governed by non-specific solvation of the symmetrical Buⁿ ₄N⁺ cation.     

Electrochemical transformations of monooxa- and dioxabicycloalkenes and-bicycloalkanes

Electrolysis of 2-oxa- and 2,5-dioxabicyclo[n.4.0]alk-1(6)0enes (n=4, 10) under conditions of direct undivided anodic oxidation in methanol results in their electrochemical mono-and dimethoxylation; electrolysis of the corresponding 2-oxa-and 2,5-dioxabicycloalkanes involves electrochemical cleavage of the bridging carbon—carbon bonds followed by electrooxidative transformation into methyl ω-(2-methoxytetrahydrofuryl)-, ω-(dimethoxy-methyl)-, and ω-(1,3-dioxolan-2-yl)alkanoates. For preliminary communication, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2115–2122, November, 1999.     

Study on dynamic interfacial tension of 3-dodecyloxy-2-hydroxypropyl trimethyl ammonium bromide at liquid/liquid interface

Dynamic interfacial tension between aqueous solutions of 3-dodecyloxy-2-hydroxypropyl trimethyl ammonium bromide (R₁₂HTAB) and n-hexane were measured using the spinning drop method. The effects of the R₁₂HTAB concentration (the concentration below the CMC) and temperature on the dynamic interfacial tension have been investigated; the reason of the change of dynamic interfacial tension with time has been discussed. The effective diffusion coefficient, D_a, and the adsorption barrier, _a, have been obtained from the experimental data using the extended Word–Tordai equation. The results show that the dynamic interfacial tension becomes smaller while _a becomes higher with increasing R₁₂HTAB concentration in the bulk aqueous phase. D_a decreases from 5.56 × 10⁻¹² m⁻² s⁻¹ to 0.87 × 10⁻¹² m⁻² s⁻¹ while _a increases from 5.41 kJ mol⁻¹ to 7.74 kJ mol⁻¹ with the increase of concentration in the bulk solution of R₁₂HTAB from 0.5 × 10⁻³ mol dm⁻³ to 4 × 10⁻³ mol dm⁻³. Change of temperature affects the adsorption rate through altering D_a and _a. The value of D_a increases from 5.56 × 10⁻¹² m⁻² s⁻¹ to 13.98 × 10⁻¹² m⁻² s⁻¹ while that of _a decreases from 5.41 kJ mol⁻¹ to 5.07 kJ mol⁻¹ with temperature ascending from 303 K to 323 K. The adsorption of surfactant from the bulk phase into the interface follows a mixed diffusion–activation mechanism, which has been discussed in the light of interaction between surfactant molecules, diffusion and thermo-motion of molecules.     

氢键构筑网络结构的三正丁基锡羧酸酯的合成、结构及抗癌活性

微波辐射条件下,μ-氧-双(三正丁基锡)分别与二苯乙醇酸、2-氯烟酸反应,合成了三正丁基锡羧酸酯(n-Bu)₃SnO₂CR(H₂O)[R:C(OH)Ph₂(1),C₅NH₃Cl(2)]。经IR、¹H和¹³C NMR、元素分析及X-射线单晶衍射表征结构。配合物1、2均属正交晶系,空间群分别为Pbca和P2₁2₁2₁,配基与中心锡原子均构成五配位畸变三角双锥构型。1和2晶体中,存在着多种氢键作用,分别连接扩展成二维和三维超分子网络。初步测试表明:1和2对人癌细胞Colo205、HepG2、MCF-7、Hela、NCI-H460增殖均有较强的抑制作用,尤其对MCF-7、Hela、NCI-H460的抑制作用均大大优于卡铂,且1的抗肿瘤活性更优于2。     

氢键构筑网络结构的三正丁基锡羧酸酯的合成、结构及抗癌活性

微波辐射条件下, μ-氧-双(三正丁基锡)分别与二苯乙醇酸、2-氯烟酸反应, 合成了三正丁基锡羧酸酯(n-Bu)₃SnO₂CR(H₂O)[R:C(OH)Ph₂ (1), C₅NH₃Cl (2)]。经IR、1H和13C NMR、元素分析及X-射线单晶衍射表征结构。配合物1、2均属正交晶系, 空间群分别为Pbca和P2₁2₁2₁, 配基与中心锡原子均构成五配位畸变三角双锥构型。1和2晶体中, 存在着多种氢键作用, 分别连接扩展成二维和三维超分子网络。初步测试表明:1和2对人癌细胞Colo205、HepG2、MCF-7、Hela、NCI-H460增殖均有较强的抑制作用, 尤其对MCF-7、Hela、NCI-H460的抑制作用均大大优于卡铂, 且1的抗肿瘤活性更优于2。     

Kinetics of the Vapor-Phase Decomposition of Mtbe (Methyl Tert-Butyl Ether) over h3pw12o40/sio2

A kinetic study on the vapor-phase MTBE decomposition over H₃PW₁₂O₄₀/SiO₂ was carried out. Possible kinetic mechanisms are proposed and discussed. Rate expressions were ultimately developed after several verification processes.     

Lysozyme binding to poly(4-vinyl-N-alkylpyridinium bromide)

The adsorption behavior of polycations at ionic strengths (I) ranging from 0.001 to 0.1 onto silicon wafers was studied by means of ellipsometry, contact angle measurements and atomic force microscopy (AFM). Polycations chosen were bromide salts of poly(4-vinylpyridine) N-alkyl quaternized with linear aliphatic chains of 2 and 5 carbon atoms, QPVP-C2 and QPVP-C5, respectively. Under I=0.001 the reduction of screening effects led to low adsorbed amounts of QPVP-C2 or QPVP-C5 (1.0±0.1 mg/m²), arising from the adsorption of extended chains. Upon increasing I to 0.1, screening effects led to conformational changes of polyelectrolyte chains in solution and to higher adsorbed amount values (1.9±0.2 mg/m²). Advancing contact angle θ_a measurements performed with water drops onto QPVP-C2 and QPVP-C5 adsorbed layers varied from (45±2)° to (50±5)°, evidencing the exposure of both hydrophobic alkyl groups and charged moieties. The adsorption of lysozyme (LYZ) molecules to QPVP-C5 layers was more pronounced than to QPVP-C2 films. Antimicrobial effect of LYZ bound to QPVP-C2 or QPVP-C5 layers or to Si wafers was evaluated with enzymatic assays using Micrococcus luteus as substrates. The adsorption behavior of QPVP-C2 and QPVP-C5 at the water–air interface was studied by means of surface tension measurements. Only QPVP-C5 was able to reduce water surface tension. Mixtures of LYZ and QPVP-C5 were more efficient in reducing surface tension than pure LYZ solution, evidencing co-adsorption at liquid–air interface. Moreover, antimicrobial action observed for mixtures of LYZ and QPVP-C5 was more pronounced than that measured for pure LYZ. Hydrophobic interaction between LYZ and QPVP-C5 in solution seems to drive the binding and to preserve LYZ secondary structure.     

Formation of cobalt(iii) cations with semiquinonediimine ligands

The reactions of polynuclear cobalt(ii) trimethylacetates [Co(OH) _n (OOCCMe₃)_2–n ] _x , Co₆(₃-OH)₂(OOCCMe₃)₁₀(HOOCCMe₃)₄, or Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with an excess of N-phenyl-o-phenylenediamine (1) in toluene followed by treatment with atmospheric oxygen afforded the diamagnetic complex [Co{²-(NPh)(NH)C₆H₄}₂{¹-(NH₂)C₆H₄(NPhH)}]⁺(Me₃CCOO...H...OOCCMe₃)^– (3), whose cation contains the Co^III atom. The reaction of Co₄(₃-OH)₂(OOCCMe₃)₆(HOEt)₆ with a deficient amount of diamine 1 in acetonitrile under an argon atmosphere gave rise to the antiferromagnetic ionic complex [Co{²-(NPh)(NH)C₆H₄}₂MeCN]⁺[Co₂(₂,²-OOCCMe₃)(₂-OOCCMe₃)₂(²-OOCCMe₃)₂]^–·2MeCN (4), whose cation is an isoelectronic analog of the cation in complex 3. The structures of the new compounds were established by X-ray diffraction analysis.