Infrared absorption spectra of Aerosol-OT homologous sodium dialkylsulfosuccinates and the effect of crystal polymorphism on the environment of the succinate segment

A homologous series of sodium dialkylsulfosuccinates, which are straight-chain analogues of Aerosol-OT with various chain lengths (dimethyl, diethyl, dibutyl, dihexyl, diheptyl, dioctyl, didecyl, diundecyl and didodecyl), has been synthesized. In order to assign the IR bands of the CH₂ scissoring and CH deformation modes of the succinate segment, sodium dideuteratedmethylsulfosuccinate and sodium dideuteratedethylsulfosuccinate have also been synthesized. IR absorption spectra have been recorded for these mono-, di- and multihydrate samples in the solid state. In particular, IR bands in the 1250–1500 cm⁻¹ region have been compared for sodium dimethylsulfosuccinate, sodium diethylsulfosuccinate and sodium diheptylsulfosuccinate, whose crystal structures are known. The CH₂ scissoring and CH deformation modes of the succinate CH₂-CH portion strongly depend upon the environment of hydration and on the length of the hydrocarbon portions. Received: 26 April 1999 Accepted in revised form: 15 June 1999     

Inhibition activity of ethyleneglycol and its oligomers on tin electrode

Voltammetry and electrochemical impedance spectroscopy were applied to investigate the inhibition activity of ethyleneglycol and its oligomers on tin electrode in strong acidic sulfate solutions. Tetraethyleneglycol was found to be the most active substance among compounds HO–(CH₂–CH₂–O) _m –H (m≤4) that retards diffusion-controlled Sn(II) reduction due to its inhibitive adsorption. This rather slow process is controlled both by diffusion and electrosorption steps. A comparison of exchange current densities obtained in the presence of different polyethers shows that the length of the hydrocarbon chain is the main factor responsible for inhibition activity of such substances on tin electrode.     

Collisionally activated dissociation spectra of protonated methyl N-alkanoates studied using a triple quadrupole

The collisionally activated dissociation (CAD) spectra of protonated methyl n-alkanoates CH₃ (CH₂)_nCOOCH₃ with n = 1?9 were studied using a triple quadrupole. The influence of hydrocarbon chain length and collision energy on characteristic fragment ions such as those due to the loss of methanol was examined. It was found that most characteristic fragment ions became less important in the CAD spectra with increasing chain length of the esters and finally disappeared in the higher members of the series. Special care would have to be taken when trying to use such neutral losses in analysis for identifying the presence of a certain class of compounds.     

On the protonated state of amidinium-like diaromatic derivatives: X-ray and UV studies

We present the crystal structures of the chloride salts of the mono-guanidinium 1 (–CH₂CH₂– linker) and the bis-isouronium 2 (–O– linker) that have been resolved by us indicating that these compounds are diprotonated in the solid state as informed by the counterions positions. To determine the pK _a values of these compounds as well as those of their analogues 3 (mono-2-aminoimidazolinium with a –CH₂CH₂– linker) and 4 (mono-guanidinium with a –O– linker), the corresponding UV–Vis titrations were carried out. Thus, in aqueous solution compounds 1, 3 and 4 were present as mono-cationic species while derivative 2 was a bis-cation.     

Structural features of disubstituted polyacetylenes with bulky substituents at double bonds

The structural features of polyacetylenes carrying two substituents at double bonds with the general formula [-C(CH₃)=CR-] _n , where R = Si(CH₃)₃, -Ge(CH₃)₃, or CH(CH₃)₂, are studied. It is shown that the experimental IR and Raman spectra of the polymers and the theoretically calculated vibrational spectra for the model polymers consisting of three units coincide well with experimental data. All bands in the IR spectra are interpreted. The potential curves of internal rotation are calculated and constructed; high values of rotation barriers indicate a high rigidity of chains for all polymers of interest. The orthogonal arrangement of neighboring monomer units and, as a result, the absence of electron-density conjugation over the polymer chain are revealed. Charges on atoms and electron density on bonds of the monomer unit obtained from theoretical calculations indicate the presence of strong polarization of all bonds, including the -C=C- bond. This effect causes a shift in the frequencies of stretching vibrations due to double bonds in the IR spectra of polyacetylenes with Si- and Ge-containing side substituents toward the longwave region. For polyacetylene with hydrocarbon side substituents -CH(CH₃)₂, such polarization is absent.     

Thermodynamics of the Interaction of a Homologous Series of Amino Acids with Sorbitol

The apparent molar volumes V _2,φ , apparent molar isentropic compressibilities K _S,2,φ , and enthalpies of dilution of aqueous glycine, alanine, α-amino butyric acid, valine, and leucine have been determined in aqueous 1.0 and 2.0 mol⋅dm⁻³ sorbitol solutions at 298.15 K. These data have been used to calculate the infinite dilution standard partial molar volumes V_2,m⁰V_{2,m}^{0}, partial molar isentropic compressibilities K_S,2,m⁰K_{S,2,m}^{0}, and enthalpies of dilution Δ_dil H ⁰ of the amino acids in aqueous sorbitol, along with the standard partial molar quantities of transfer of the amino acids from water to aqueous sorbitol. The linear correlation of V_2,m⁰V_{2,m}^{0} for this homologous series of amino acids has been utilized to calculate the contribution to V₂⁰V_{2}^{0} of the charged end groups (NH₃⁺\mathrm{NH}_{3}^{+}, COO⁻), the CH₂ group, and other alkyl chains of the amino acids. The results for the standard partial molar volumes of transfer, compressibilites and enthalpies of dilution from water to aqueous sorbitol solutions have been correlated and interpreted in terms of ion–polar, ion–hydrophobic, and hydrophobic–hydrophobic group interactions. A comparison of these thermodynamic properties of transfer suggest that an enhancement of the hydrophilic/polar group interactions is operating in ternary systems of amino acid, sorbitol, and water.     

A study of alkyl radicals in the matrix of polycrystallinen-alkane γ-irradiated at 77 K

The composition of alkyl radicals (AR) formed by γ-radiolysis (T=77 K) of polycrystallinen-alkanes with different lengths of the carbon chain (C(5), C(7), C(10), C(11), and C(18)) and their polymeric analog (polyethylene) was estimated from the ESR spectra. The ESR spectra of the irradiatedn-alkanes are superpositions of the signals from the H₃CC^.HCH₂− and −CH₂C^.HCH₂− radicals, whose HFS constants with α and β protons as well as the equilibrium conformation are independent of the chain length of then-alkane molecule. A dependence of the concentration of the radicals on the chain length ofn-alkane was found. The absence of the −CH₂C^.H₂ radicals that may arise upon H atom elimination from the Me fragments of then-alkane molecules is most likely related to the transfer of excitation energy from the Me group to the neighboring methylene fragment and the transformation of the −CH₂C^.H₂ radicals into H₃CC^.HCH₂− radicals. With account for this, the concentrations of the AR formed were suggested to be proportional to the number of H atoms at the corresponding C atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1034–1037, June, 2000.     

Partial Molar Volumes of Some of α-Amino Acids in Binary Aqueous Solutions of MgSO4·7H2O at 298.15 K

The apparent molar volume, V ^o _{φ, 2}, of glycine, alanine, α-amino-n-butyric acid, valine and leucine have been determined in aqueous solutions of 0.25, 0.5 and 1.0 mol⋅dm⁻³ magnesium sulfate, and the partial specific volume from density measurements at 298.15 K. These data have been used to calculate the infinite dilution apparent molar volume, V ^o _2,m , group contribution of amino acids and partial molar volume of transfer, Δ_tr V _2,m ^o, from water to aqueous magnesium sulfate solutions. The linear correlation of V _2,m ^o for a homologous series of amino acids has been utilized to calculate the contributions of charged end groups (NH₃ ⁺, COO⁻), CH₂ - groups and other alkyl chains of amino acids to V _2,m ^o. The results for Δ_tr V _2,m ^o of amino acids from water to aqueous magnesium sulfate solutions have been interpreted in terms of ion-ion, ion-polar, hydrophilic-hydrophilic and hydrophobic-hydrophobic group interactions. The values of the standard partial molar volume of transfer for the amino acids with different hydrophobic contents, from water to aqueous MgSO₄ are in general positive, indicating the predominance of the interactions of zwitterionic/hydrophilic groups of amino acids with ions of the salt. The hydration number decreases with increasing concentration of salt. The number of water molecules hydrated to amino acids decreases, further strengthening the predominance of ionic/hydrophilic interactions in this system.     

Structure and crystallization of sub-elementary fibrils of bacterial cellulose isolated by using a fluorescent brightening agent

The structure and crystallization of carefully isolated sub-elementary fibrils (SEFs) of bacterial cellulose have been investigated using TEM, WAXD, and high-resolution solid-state ¹³C NMR. The addition of a suitable amount of fluorescent brightener (FB) to the incubation medium of Acetobacter xylinum effectively suppressed the aggregation of the SEFs into the microfibrils, as previously reported. However, this study confirmed for the first time that serious structural change in the SEFs occurs during the removal of excess FB by washing with buffer solutions having pH values higher than 6 or with the alkaline aqueous solution that was frequently used in previous studies. In contrast, the isolation of unmodified SEFs was successfully performed by utilizing a washing protocol employing pH 7 citrate–phosphate buffer solution containing 1% sodium dodecyl sulfate. High-resolution solid-state ¹³C NMR and WAXD measurements revealed that the SEFs thus isolated are in the noncrystalline state in which the pyranose rings of the almost parallel cellulose chains appear to be stacked on each other. The respective CH₂OH groups of the SEFs adopt the gt conformation instead of the tg conformation found in cellulose I _α and I _β crystals, and undergo significantly enhanced molecular motion in the absence of intermolecular hydrogen bonding associated with these groups. The main chains are also subject to rapid motional fluctuations while maintaining the parallel orientation of the respective chains, indicating that the SEFs have a liquid crystal-like structure with high molecular mobility. Moreover, the SEFs crystallize into cellulose I _β when the FB molecules that may adhere to the surface of the SEFs are removed by extraction with boiling 70 v/v% ethanol and 0.1N NaOH aqueous solution. On the basis of these results, the crystallization of the SEFs into the I _α and I _β forms is discussed, including the possible formation of the crystalline-noncrystalline periodic structure in native cellulose.     

Unique morphological and thermal behaviors of reorganized poly(ethylene terephthalates)

Bulk poly(ethylene terephthalate) PET has been reorganized both morphologically and conformationally by processing from its inclusion complex (IC) formed with γ‐cyclodextrin (CD). In the narrow channels of its γ‐CD‐IC crystals the included guest PET chains are isolated from neighboring PET chains and the ethylene glycol (EG) units adopt the highly extended g±tg? kink conformations, whose cross‐sectional diameters are ～80% of the diameter of the fully extended, all‐trans crystalline PET conformer, though they are nearly (～95%) as extended. When the highly extended, unentangled guest PET chains are coalesced from their γ‐CD‐IC crystals by exposure to hot water, host γ‐CDs are removed and the PET chains are presumably consolidated into a bulk sample with a morphology and constituent chain conformations not normally found in PET samples solidified from their randomly coiling, possibly entangled, disordered melts and solutions. Observations by polarized light and atomic force microscopies provide visual evidence for widely different semicrystalline morphologies developed in coalesced and as‐received PETs when crystallized from their melts, with possibly chain extended, small crystals and spherulitic, chain‐folded, large crystals, respectively. DSC observations reveal that coalesced PET is rapidly crystallizable from the melt, while as‐received PET is slow to crystallize and is easily quenched into a totally amorphous sample. Analyses of ¹³C‐NMR data strongly indicate that the PET chains in the noncrystalline regions of the coalesced sample remain predominantly in the highly extended kink conformations, with g±tg? EG units, which are required by their inclusion into PET‐γ‐CD‐IC crystals, while the predominantly amorphous PET chains in the as‐received sample have high concentrations of gauche± ? CH₂? CH₂? and trans ? O? CH₂? ,? CH₂? O? EG bond conformations. ¹³C‐NMR T₁(¹³C) and T_1ρ(¹H) relaxation studies show no evidence of a glass transition for coalesced PET, while the as‐received sample shows abrupt changes in both the MHz [T₁(¹³C)] and kHz [T_1ρ(¹H)] motions at T ～ T_g. Preliminary observations of differences in their macroscopic properties are attributed to the very different morphologies and conformations of the constituent chains in these PET samples. Apparently the kink conformers in the noncrystalline regions of coalesced PET are at least partially retained for extended periods even in the melt and are rapidly crystallized upon cooling. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 386–394, 2004     

Aggregation behaviour of hydrophobically modified poly(allylammonium) chloride

 The behaviour of hydrophobically modified poly(allylammonium) chloride having octyl, decyl, dodecyl and hexadecyl side chains has been studied in aqueous solution using fluorescence emission techniques. Micropolarity studies using the I ₁/I ₃ ratio of the vibronic bands of pyrene show that the formation of hydrophobic microdomains depends on both the length of the side chain and the polymer concentration. The I ₁/I ₃ ratio of the polymers with low hydrophobe content (less than 5% mol) changes substantially when reaching a certain concentration. These changes are assigned to aggregation originating from interchain interactions. This behaviour is also confirmed by the behaviour of the monomer/excimer emission intensities of pyrenedodecanoic acid used as a probe. For polymers having dodecyl side chains and hydrophobe contents higher than 10%, aggregates are formed independently of the polymer concentration. Anisotropy measurements show that microdomains resulting from the inter- and/or intramolecular interactions are similar to those observed for cationic surfactants. Viscosity measurements show that the coil dimensions are substantially decreased for the polymers having high hydrophobe contents, indicating intramolecular associations. Received: 10 November 1999/Accepted: 7 April 2000     

Two 3-D Supramolecular Networks Containing Dimeric {Cu2X2} Cluster Units

Abstract  Two new 3-D supramolecular compouds: [Cu₂X₂(Hpyba)₂]_n (X = Br (1), I (2), Hpyba = 4-pyridin-4-yl-benzoic acid) have been hydrothermally synthesized and structurally characterized. Although both compounds exhibit different space groups, they have a similar structure. Each {Cu₂X₂} cluster unit interconnects to form a 1D stair-step chain. The Saturated Hpyba ligands are regularly appended to both sides of main chain, linked via N atoms of ligands. These infinite chains are further linked by H-bonds and π–π interactions to form a 3-D supramolecular network structure. The thermal stability of 1 and 2 was investigated by thermogravimetric measurements. Graphical Abstract  Two new 3-D supramolecular compouds [Cu₂X₂(Hpyba)₂]_n (X = Br(1), I(2), Hpyba = 4-pyridin-4-yl-benzoic acid) have been obtained under hydrothermal conditions. Both compounds exhibit a 1D stair-step chain structure based on the {Cu₂X₂} cluster units. These infinite chains are further linked by H-bonds and π–π interactions into forming a 3-D supramolecular network with two types of channels along different directions.      

Synthesis and Antiinflammatoryand Anticancer Activity Evaluation of Some Condensed Pyrimidines

Summary.  Upon condensation with 4-isothiocyanato-4-methyl-2-pentanone, 2,3-diaminonaphthalene and N-aminoethyladenosine gave in good yields substituted pyrimidonaphthoimidazole and imidazopyrimidine thione. Refluxing pyrimidobenzthiazole with methanol H₂SO₄ at pH∼1 resulted in S-methyl pyrimidobenzthiazole in moderate yield. Pyrimidobenzimidazole derivatives could be reacted to S-alkylated and N-acylated derivatives by refluxing with ethyl bromoacetate in the presence of anhydrous potassium carbonate in THF and by heating in an acetic acid/acetic anhydride mixture. Heating of pyrimidobenzimidazole with 75% aqueous H₂SO₄ on a water bath ended up in a rearranged product. All compounds gave correct ¹H NMR, IR, and HR mass spectra. Results of antiinflammatory, analgesic, and anticancer activity screening of the new compounds are described. Received October 29, 1999. Accepted (revised) January 13, 2000     

Giant colloidal crystals of fluorine-containing polymer spheres in exhaustively deionized aqueous suspensions and in the presence of sodium chloride

 Gigantic colloidal single crystals (2–6 mm) are formed for fluorine-containing polymer spheres (120–210 nm in diameter) in exhaustively deionized aqueous suspensions. The spheres used are poly(tetrafluoroethylene) (PTFEA and PTFEB), copolymer of tetrafluoroethylene and perfluorovinylether (PFA) and copolymer of tetrafluoroethylene and perfluoropropylene (PTP). The phase diagrams of these spheres are obtained in the deionized suspensions and also in the presence of sodium chloride for PFA. The critical sphere concentrations of crystal melting (φ _c) for these spheres are around 0.0006 in volume fraction, which are close to, but slightly larger than, those of monodispersed polystyrene spheres (φ _c ≈ 0.00015) and colloidal silica spheres(φ _c = 0.0002–0.0004) reported previously. The crystals are largest when the sphere concentrations are a bit higher than the φ _c value and their size decreases as the sphere concentration increases. Reflection spectra are taken in sedimentation equilibrium as a function of the height from the bottom of the suspension. The static elastic modulus is estimated to be 10.8 and 28.7 Pa for PTFEA and PTP spheres at the sphere concentrations 0.00325 and 0.00322 in volume fraction, respectively. Received: 27 October 1999 Accepted in revised form: 16 November 1999     

Radiation polymerization and copolymerization of fluorinated acrylates and methacrylates induced by γ-rays

Fluorinated acrylates and methacrylates radiolyzed at 77 K polymerize upon heating in the range from the glass-transition to the melting temperature. In the case of acrylates, the temperature range of postradiation polymerization increases by more than 100 K with the increasing chain length of the perfluorinated substituent from C₂F₄ to C₈F₁₇. The introduction of perfluorinated substituents into methacrylate molecules makes it possible to obtain them in the glassy state and to carry out low-temperature postradiation polymerization, in contrast to their hydrocarbon analogues. The termination rate constant of the polymerization of fluorinated methacrylates has a lower value as compared to conventional methacrylates. The formation of crosslinked structures is suppressed during the copolymerization of fluorinated acrylates with methacrylates. The ESR spectra of growing polymer radicals of fluorinated acrylic ∼CH₂C^·H(COOCH₂C₆F₁₃)∼ and methacrylic CH₂C^·(CH₃)(COOCH₂C₂F₄H)∼ monomers have been identified.     

Synthesis and Characterization of New Unsymmetrically Substituted Phthalocyanines

Summary.  Unsymmetric metallophthalocyanines (M=Zn, Co, Ni) carrying alkylthio and acetyloxyethylthio groups on peripheral positions were prepared from 4,5-bis-alkylthio-phthalonitrile, 4,5-bis-(acetyloxyethylthio)-phthalonitrile, and the corresponding anhydrous metal salts Zn(CH₃COO)₂, NiCl₂, and CoCl₂. The extremely soluble compounds were characterized by their IR, ¹H NMR, and UV/Vis spectra. Their long wavelength absorption band was found to be bathochromically shifted; their solubility is superior to that of symmetrical phthalocyanines. Received July 27, 1999. Accepted (revised) September 30, 1999     

IR and Raman spectroscopic study of the photopolymerization of Langmuir-Blodgett films of acetylenic acids

The UV induced photopolymerization of Langmuir-Blodgett films of lead salt of 2-docosynoic acid (CH₃(CH₂)₁₈C=CCOOH) is studied using IR and Raman spectroscopy. It is found that the films are a highly ordered system with trans-configuration of alkyl chains and a bridged complex generated between the carboxyl group and the lead ion. Based on a change in the absorption band intensity in the IR spectra corresponding to the triple bond vibration, the degree of polymerization depending on the irradiation time is determined. In the Raman spectra, a peak at ∼1635 cm⁻¹ appears during polymerization, which corresponds to the C=C double bond. The formation of conjugated double bonds in these systems is observed for the first time. During polymerization, methylene chains of molecules retain trans-configuration; the structural ordering of molecules in the film is observed.     

Vibrational spectra and structural features of carbene analogs ElII(OCH2CH2NMe2)2 and ClElIIOCH2CH2NMe2 (ElII = Ge, Sn, Pb)

Vibrational spectra of compounds of divalent Group 14 elements El^II(OCH₂CH₂NMe₂)₂ with El^II = Ge (1), Sn (2), Pb (3) and ClEl^IIOCH₂CH₂NMe₂ with El^II = Ge (4) and Sn (5) were measured for the first time and analyzed within the framework of DFT calclations. Monomeric compounds 1 and 2 whose molecules are stabilized only through intramolecular coordination were confirmed to be isostructural. Unlike 1 and 2, plumbylene 3 is a polymer in both solution and the crystalline state; the latter was confirmed by X-ray diffraction analysis. The ν^s _C-N stretching frequency in the CH₂NMe₂ fragment was shown to decrease by 80–100 cm⁻¹ owing to the formation of the coordination bond El←N. To elucidate the mechanism of a dynamic flip-flop process suggested earlier based on the broadening of some signals in the NMR spectra of compounds 1 and 4, the Raman spectra of solutions of compounds 1 and 2 in THF and Py were obtained. These experiments revealed no equilibrium with participation of a stable form with one coordination bond El←N cleaved along with the starting molecule. This is consistent with the results of the corresponding quantum chemical calculations of thermo-dynamic parameters. A somewhat different, more probable mechanism of the dynamic process was proposed, which involves an overturn of the CH₂NMe₂ fragment with cleavage of the El←N bond in the transition state only.     

CPI induction of liquid crystal behaviour in triphenylenes with a mixture of hydrophobic and hydrophilic side chains

2,3,6,7,10,11-Hexasubstituted triphenylenes have been synthesized that contain a mixture of hydrophobic (C₆H₁₃O) and hydrophilic (CH₃OCH₂CH₂OCH₂CH₂O) side chains. At one extreme HAT6 (1a) (six hydrophobic chains) shows thermotropic behaviour and at the other TP6EO2M (1e) (six hydrophilic chains) shows lyotropic behaviour. Of the triphenylenes with a mixture of hydrophobic and hydrophilic side chains, only the triphenylene with one hydrophilic side chain and five hydrophobic side chains (1b) gives a thermotropic columnar phase. None of the others show liquid crystal behaviour. However, all of these triphenylenes form binary 1:1 compounds when mixed with PDQ9 (2a) and with PTP9 (2b). These CPI (complimentary polytopic interaction) stabilized compounds give thermotropic hexagonal columnar phases over wide temperature ranges.     

Enthalpies of formation of radicals and the mass spectra of the products of tetrafluoroethylene polymerization in acetone

The mass spectra of the dissociative electron-impact ionization products of telomers formed upon the radiation-chemical telomerization of tetrafluoroethylene in acetone were measured over the range of m/z from 1 to 204. The most intense bands at m/z = 43, 51, and 57 were attributed to the CH₃CO⁺, CF₂H⁺ and CH₃COCH₂⁺ cations—the main dissociation products of the H(C₂F₄) _n CH₂COCH₃ telomers. The telomer composition was consistent with a radical telomerization mechanism, in which chain growth and chain transfer are due to the formation of the CH₃COCH₂^· radical. Based on published data supplemented with quantum-chemical calculations, the enthalpies of formation of the radicals R(CF₂) _n (n = 2–8; R = H, CH₃, CH₃CO, and CH₃COCH₂) were tabulated. The formation of telomers with the same terminal groups is consistent with thermodynamic data and a polymerization mechanism in which the chain growth reaction is diffusion-limited and the chain transfer reaction is activated hydrogen-atom transfer.