Pyridine Medium Research Articles

INVESTIGATION OF REACTIONS OF INTERACTION OF CELLULOSE NITRIC ESTERS WITH CARBOXYLIC ACID CHLORIDES

The chemical interaction of high-nitrogen cellulose ether with acetic, propionic, butyric and isobutyric acids has been studied. The general laws and features of the electrophilic substitution of functional groups of cellulose nitroesters are revealed. The preferred directions of the chemical interaction of cellulose nitrate with carboxylic acid chlorides are established: O-acylation of nitrate and hydroxyl groups; O-acylation of the glucopyranose ring; O-acylation of the ether bond with depolymerization of the chain of an SC molecule; hydrolysis of nitrate groups; destruction of the chain of a macromolecule of nitric acid ester with the formation of water-soluble organic compounds. The structure, properties and possibilities of using synthesized mixed cellulose ethers were studied. Effective methods have been developed for the chemical modification of cellulose nitrates with carboxylic acid chlorides. The probable directions of the reaction of the interaction of cellulose nitrates with electrophilic reagents are predicted based on quantum-chemical calculations of point charges on the atoms of the reacting molecules. The reactivity of highly substituted cellulose nitrates in reactions with carboxylic acid chlorides has been established. The optimal conditions for the interaction of cellulose nitrates with carboxylic acid chlorides have been identified and a mathematical model of the reaction kinetics has been constructed. The possibility of a directed change in the composition of chemically modified cellulose nitrates depending on the synthesis conditions has been established. As a result of the combined use of physicochemical research methods, the chemical composition was determined and the structure of the synthesized compounds was determined: cellulose acetyl nitrates, cellulose propionyl nitrates, cellulose butyryl nitrates, and cellulose isobutyryl nitrates. Using gel chromatography, it was found that the molecular weight characteristics of the synthesized samples are directly dependent on the conditions of their synthesis. It was found that electrophilic substitution of the functional groups of cellulose nitrate proceeds more intensively in the pyridine medium.

Sulfation of Betulin with Chlorosulfonic Acid in Pyridine

It was found that when betulin is sulfated with chlorosulfonic acid in pyridine medium, 3,28-disulfate of betulin is formed in a stable salt form. Under optimal synthesis conditions: temperature 70 °C, duration 2 hours, molar ratio betulin / chlorosulfonic acid 4.0, betulin is completely converted into betulin 3.28-disulfate. The structure and composition of betulin 3,28-disulfate were confirmed by elemental analysis, IR, Raman and 13C NMR spectroscopy. Betulin 3,28-disulfate was isolated both in the form of an unstable H + -form and in a stable forms of sodium and pyridinium salts. Sodium salt of 3,28-disulfate is a needle-like crystals collected in cobweb-like aggregates. The sodium salt of 3,28-disulfate has mycellar properties, the critical concentration of mycellar formation is 0.23 mmol / L.

Design, Synthesis and Antiinflammatory Evaluation of 5(6)-(un)-substituted-1H-Benzimidazol-2-ylthioacetylpiperazine Derivatives

Benzimidazole-2-thione derivatives are known to possess broad spectrum of biological activities, and the most prominent being the antiinflammatory activity. The synthesis of these compounds involve three steps, William’s reaction of 5(6)-(un)-substituted-1H-benzimidazol-2-thiols with chloroacetic acid in presence of sodium hydroxide and refluxing, which was further reacted with acetic anhydride in pyridine medium on a steam bath followed by hydrolysis with a N-mono substituted piperazine in ethanol medium under reflux conditions to get 5(6)-(un)-substituted(1H-benzimidazol-2-yl-thio)acetyl piperazine derivatives. Molecular docking experiments were carried out against cox-2 enzyme using GOLD software 5.1.0. Docking studies revealed important binding interactions of synthesized derivatives with cox-2 enzyme indicating non-selective interactions, which were in agreement with the in vivo antiinflammatory activity. Absorption, distribution, metabolism, and excretion properties of the synthesized derivatives were determined by QikProp. These derivatives were tested in the carrageenan-induced rat paw edema model to determine the antiinflammatory activity.

Mordenite etching in pyridine: Textural and chemical properties rationalized by toluene disproportionation and n-hexane cracking

Chemical etching with hydrofluoric acid in pyridine medium has been developed as efficient strategy for the crystal engineering of mordenite zeolites. Contrary to the HF etching in aqueous medium, the etching in pyridine allows to preserves the global composition and acidity of parent mordenites. Zeolites etched in pyridine have a similar distribution of Brønsted acid sites (BAS) as the parent, i.e. 16% in 8-MR channels, 19% at the intersection between side pockets and 12-MR channels and 65% in the 12-MR channels. Etching in aqueous HF failed to preserve BAS distribution due to strong dealumination, which further leads to enlargement of side pockets. Mordenites etched with HF in pyridine allow for superior catalytic performance in both n-hexane cracking and toluene disproportionation. It has been evidenced that only the BAS located in the 8-MR side pockets prove active for the toluene disproportionation at 450 °C, while for n-hexane cracking at 541 °C BAS in both 12-MR channels and 8-MRs pockets catalyze the reaction, yet BAS in side pockets are more active (1.5 times). Moreover, Lewis acid sites generated during the post-synthetic treatments exalt the strength of the active sites, which multiplies TOFs of the active sites by two.

Synthesis, Characterization and Applications of Certain New Poly (ester amides), Their Blend Nanofibers

Abstract A new series of four aromatic poly(ester amides) were synthesized by direct polycondensation from 2,5-pyridine dicarboxylic acid as common diacid and 4, 4’ - diamino diphenyl methane as common diamine with four different diols using diphenylchlorophosphate (DPCP) in pyridine medium. The resulting polymers were found to be soluble in highly polar solvents and sparingly soluble in nonpolar solvents. The synthesized poly(ester amides) were characterized by FT-IR, 1H and 13C NMR spectra which confirmed that the monomers are well incorporated in the main chain of the poly(ester amides). The thermal phase transition behaviour of these polymers was investigated by Differential Scanning Calorimetry (DSC). X-ray diffraction (XRD) studies were carried out to determine the crystallinity of the poly(esteramides). Antibacterial activity of the polymers was studied against some pathogenic bacteria by agar well diffusion method. Blend nanofibers of the polymers with PVC were prepared by electrospinning technique. Morphological studies of the nanofibers were carried out by using Scanning Electron Microscopy (SEM). The synthesized poly(ester amides) are expected to be potential candidates for novel biomedical applications.

Anti-bacterial activity, anti-cancer activity and nanofiber formation of certain poly (ester amides) from 2,5-pyridine dicarboxylic acid

A new series of four poly(ester amides) were synthesized by direct polycondensation of 2,5-pyridine dicarboxylic acid with two different varying diols and diamines in pyridine medium using diphenylchlorophosphate as a condensation agent. The two diamines employed in the synthesis were 4,4’-diamino diphenyl methane and 1,4-diamino benzene. The arylidenediols 2,5-bis(4-hydroxy-3-methoxybenzylidene)cyclopentanone and 2,6-bis(4-hydroxy-3-methoxybenzylidene) cyclohexanone were also used. The synthesized poly(ester amides) were characterized by qualitative solubility test, FT-IR, 1H and 13C-NMR spectra. The monomeric moieties were found by spectroscopic analysis to be well incorporated in the polymer back bone. The thermal phase transition behavior of the poly(ester amides) were investigated by differential thermo gravimetry (DTG). The nanofibers of synthesized poly(ester amides) with PVC and composite fibers with PVC/nanoclay were formed by electrospinning. The morphology of these composite fibers was studied by scanning electron microscopy (SEM). These poly(ester amides) were screened for their anti-bacterial potential in vitro against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Bacillus subtilis. In vitro anti-cancer activities of synthesized polymers were also evaluated against MCF7 human breast carcinoma cells. The results show that the polymers exhibited significant anti-bacterial and anti-cancer activity.
 Keywords: Poly (ester amides), Anti-bacterial activity, Nano fiber, Anticancer activity

Mononuclear and binuclear lanthanide acetates with chelating and bridging triethanolamine ligands

The interaction of lanthanide acetates with triethanolamine in pyridine medium yields mononuclear cationic complexes [Ln(teaH3)2(MeCOO)](MeCOO)2·0.5Py (teaH3 = N(CH2CH2OH)3, Py – pyridine) in cases Ln = Ce (1) and Pr (2), and binuclear heteroleptic complexes containing deprotonated triethanolamine [Ln2(MeCOO)4(teaH2)2] (Ln = Gd (3), Dy (4), Ho (5), and Er (6)). In the complexes of the first type, tetradentate chelating triethanolamine is a neutral ligand, while the metal core of the complexes of the second type is formed of lanthanide ions and bridging oxygen atoms of deprotonated teaH3. In the processes of thermal decomposition of complexes, systematic changes related to the character of the Ln3+ ions are noted. The complexes 1–6 were characterized by dc magnetic measurements, the Dy, Ho, and Er derivatives were also investigated in ac field. In the Gd complex, antiferromagnetic interactions between the Gd3+ ions were found. Results for complex 3, along with the literature data for eight complexes with the [Gd2O2] core, allowed to complement and to confirm the correlation between the value of the exchange interaction energy JGd–Gd′ and the interionic distances DGd…Gd′ for the complexes of this type that we found earlier. Complex of Dy exhibits field-induced slow relaxation of the magnetization.

Synthesis and structures of novel tetra- and pentanuclear copper sandwich-like metallasiloxanes with pyridine ligands

Two new polyherdal copper metallasiloxanes with pyridine ligands were synthesized by the hydrolysis of triethoxyphenylsilane in the presence of NaOH and the subsequent interaction of the alkaline salt thus in situ formed with CuCl or CuCl2 in pyridine media. Depending on the salt used, tetra- or pentanuclear sandwich-like Cu-metallasiloxanes were obtained, whose structures were studied by single crystal X-ray diffraction.

Development of repaglinide microspheres using novel acetylated starches of bitter and Chinese yams as polymers

Tropical starches from Dioscorea dumetorum (bitter) and Dioscorea oppositifolia (Chinese) yams were acetylated with acetic anhydride in pyridine medium and utilized as polymers for the delivery of repaglinide in microsphere formulations in comparison to ethyl cellulose. Acetylated starches of bitter and Chinese yams with degrees of substitution of 2.56 and 2.70 respectively were obtained. Acetylation was confirmed by FTIR, 1H NMR spectroscopy. A 32 factorial experimental design was performed using polymer type and drug-polymer ratio as independent variables. Particle size, swelling, entrapment and time for 50% drug release (t50) were dependent variables. Contour plots showed the relationship between the independent factors and the response variables. All variables except swelling increased with drug: polymer ratio. Entrapment efficiency was generally in the rank of Bitter yam>Ethyl cellulose>Chinese yam. Repaglinide microspheres had size 50±4.00 to 350±18.10μm, entrapment efficiency 75.30±3.03 to 93.10±2.75% and t50 3.20±0.42 to 7.20±0.55h. Bitter yam starch gave longer dissolution times than Chinese yam starch at all drug-polymer ratios. Drug release fitted Korsmeyer-Peppas and Hopfenberg models. Acetylated bitter and Chinese yam starches were found suitable as polymers to prolong release of repaglinide in microsphere formulations.

The Interaction of 1H-Azoles With Nitrosochlorides of Adamantane Series

The interaction of nitrosochlorides based on 2-alkylidene adamantanes and 1Н-azoles in pyridine medium produced α-azolyl oximes of adamantane series. The reaction occurred as a conjugated 1,4-addition to in situ generated nitrosoalkenes acting as Michael acceptors. The structure of phenyl-[2-(4-phenyl-1Н-imidazol-1-yl)adamantan-2-yl]methanone (Е)-oxime was studied by X-ray crystallography.

Evaluation of chemically modified hydrophobic sago starch as a carrier for controlled drug delivery

The present investigation deals with the development of controlled release tablets of lamivudine using acetylated sago starch. The acetylated starch was synthesized with acetic anhydride in pyridine medium. The acetylated sago starch was tested for acute toxicity and drug–excipient compatibility study. The formulations were evaluated for physical characteristics like hardness, % friability, % drug content and weight variations. The in vitro release study showed that the optimized formulation exhibited highest correlation (R) value in the case of higuchi kinetic model and the release mechanism study proved that the formulation showed a combination of diffusion and erosion processes. There was a significant difference in the pharmacokinetic parameters (Tmax, Cmax, AUC, Vd, T1/2 and MDT) of the optimized formulation as compared to the marketed conventional tablet Lamivir® which proves the controlled release property of acetylated sago starch.

Synthesis, Characteristics and Physico-chemical Study of Some Dichloro Pyrazoles

Some new 3,5-Diaryl-1-substituted pyrazoles have been synthesized by the action of isonicotinic acid and thio-semicarbazide on 3-iodo flavanones in pyridine medium. 3-iodo flavanones obtained from 2-hydroxy-3,5-dichloro chalcones and ICl in acetic acid. Structure of these compounds has been established by chemical and spectral analysis (NMR & IR). Purity of these heterocycles was checked by TLC. The interaction of Cu(II), Co(II) with 1-carboxamido-3-(2-hydroxy-3,5-dichloro pheyl)-5-(4-methoxy phenyl) pyrazole (L1), 1-thiocarbaxomedo-3(2-hydroxy-3,5-dichloro pheyl)-5-(4-methoxy phenyl) pyrazole (L2) have been carried out by employing Bjerrum -Calvin pH metric titration technique, at 27oC in 70 % dioxane-water medium. The data obtained can be used for the determination of proton ligand formation numbers (n). From the formation curve, the proton-ligand stability constant pK values have been evaluated using half integral method. The metal ligand formation numbers (n) are estimated by using Irving Rossotti’s expression.Metal-Ligand stability constants for 1:1 complex & 1:2 complex have been calculated which are designated by letters log K1 & log K2 respectively.

Evaluation of acetylated moth bean starch as a carrier for controlled drug delivery

The present investigation concerns with the development of controlled release tablets of lamivudine using acetylated moth bean starch. The acetylated starch was synthesized with acetic anhydride in pyridine medium. The acetylated moth bean starch was tested for acute toxicity and drug–excipient compatibility study. The formulations were evaluated for physical characteristics like hardness, friability, % drug content and weight variations. The in vitro release study showed that the optimized formulation exhibited highest correlation (R) value in case of Higuchi kinetic model and the release mechanism study proved that the formulation showed a combination of diffusion and erosion process. There was a significant difference in the pharmacokinetic parameters (Tmax, Cmax, AUC, Vd, T1/2 and MDT) of the optimized formulation as compared to the marketed conventional tablet Lamivir®, which proved controlled release potential of acetylated moth bean starch.

Esterification of Chemical Functional Single-Wall Carbon Nanotubes

Two kinds of chemical functional single-wall carbon nanotubes (SWNTs) are covalently coupled into special V-type superstructure by the esterification in pyridine medium. Both SWNTs bundles and individual SWNTs can be bound effectively through the deacidification path. The esterification between different kinds of modified SWNTs takes place on their ends and the crystallinity of SWNTs are well remained during the course. Interestingly, the inclinations between coupled SWNTs are very closely to the ester bond angle (109o18’). Furthermore, the formation mechanism about the peculiar structure has been proposed in the paper. The results suggest that selected connection bonds will determine the different angles of coupled SWNTs.

Deuteration of Water Enables Self‐Organization of Phospholipid‐Based Reverse Micelles

Phospholipid-based reverse micelles are composed of branched cylinders. Their branching points are known to attract themselves and to slide along branches. The rate of this sliding is governed by the lifetime of H(D)-bonded water bridges between phospholipid molecules. This lifetime is increased when the water is deuterated. On condition that the water contains at least 40 D atoms%, water/dipalmitoylphosphatidylcholine (DPPC)/deuterated pyridine reverse micelles with the composition 1.1:1:250 (v/v) have been shown to self-organize into a liquid crystal in the 310-316 K temperature range. The mechanism of this self-organization is unraveled by following the FTIR and (1)H NMR spectra of more concentrated micelles upon heating. During the preparation of micelles, pyridine-(D(+))H(+) ions are formed. They give rise to hydron transfers, under the influence of the DPPC electric charges, evidenced by two broad FTIR absorptions above (BB1) and below (BB2) the nu(C-O) stretch. These hydron transfers occur along strong (D(+))H(+) bonds of pyridinium ions with pyridine (BB1) and DPPC C=O groups (BB2). The proton transfers at the interface of micelles, relayed in the continuous pyridine medium, create a tenuous link between separated micelles, thus facilitating their organization. Upon heating, DPPC heads shrink and DPPC chains expand to make wedge-shaped DPPC molecules. The micelles then change in shape: cylinders constrict and enclosed water drifts towards branching points, which swell. Branching points of neighboring micelles come into contact. Due to the deuteration of water these contacts are prolonged and H bonds are formed between DPPC molecules located in each branching point. Upon storage at 39 degrees C, these branching points fuse. The lateral diffusion of DPPC molecules becomes free, as evidenced by a narrowing of all (1)H NMR resonances. Upon further heating, reorganization into a liquid crystal occurs.

Physicochemical properties and antitumor activities for sulfated derivatives of lentinan

Five fractions of lentinan, a β-(1→3)- d-glucan bearing β-(1→6)- d-glucopyranosyl branches, were treated with chlorosulfonic acid for 90 min at 60 °C in pyridine medium to synthesize water-soluble sulfated derivatives having the substitution degree of 1.44–1.76. The 13C NMR spectra of the sulfated β-glucans indicated that the C-6 position was preferentially substituted by the sulfate groups. The values of the weight-average molecular weight ( M w), radius of gyration ( 〈 s 2 〉 z 1 / 2 ), and intrinsic viscosity ([ η]) of the sulfated lentinan fractions were determined by size-exclusion chromatography with multi-angle laser light scattering (SEC–MALLS) and viscometry in 0.15 M aq NaCl at 25 °C, respectively. The dependence of [ η] on M w for the sulfated lentinan was found to be [ η] = 8.93 × 10 −3 M w 0.73 ± 0.02 (mL/g) in 0.15 M aq NaCl (for M w ranging from 14.6 × 10 4 to 50.4 × 10 4). On the basis of the Yamakawa–Fujii–Yoshizaki (YFY) theory, the conformational parameters of the sulfated lentinan were calculated as 950 nm −1 for the molar mass per unit contour length ( M L), 4.8 nm for the persistence length ( q), and 13.9 for the characteristic ratio ( C ∞), indicating relatively extended single flexible chains in solution. The sulfated glucan fractions exhibited in vitro antiproliferative activities against sarcoma 180 (S-180) cells, and their inhibition ratios were lower than that of the triple-helix lentinan, but higher than that for the one with single random-coil lentinan chains.

Pressure dependence of the Raman active vibrations in InP–CdS hybrid nanoparticles

AbstractThe effects of pressure on the confined and surface‐optical (SO) vibrations in core‐shell InP–CdS colloidal nanoparticles are explored experimentally by Raman scattering and theoretically using the phenomenological macroscopic approach (PMA) (F. Comas and C. Trallero‐Giner, Phys. Rev. B 67, 115301 (2003); C. Trallero‐Giner et al., to be published [1]). Experiments on two sample ensembles are carried out to P = 6.5 GPa at 373 K and 230 K (including laser heating) using diamond‐cells with 4:1 methanol:ethanol and pyridine media. We observe the pressure‐induced shifts of the peaks due to the confined LO‐ and TO‐like core modes, and of the broad feature assigned to SO vibrations at the CdS‐shell surface. PMA calculations are performed for the confined modes and the ℓ = 1, 2 SO modes in spherical geometry using pressure‐dependent bulk parameters as input. We compute the frequencies for different core radii and shell‐to‐core radius ratios γ. The best fit to the pressure data is found for an InP core diameter of 45 ± 10 A, and γ ∼ 1.1–1.4 depending on the sample ensemble and the value of ℓ. The effects of pressure on the InP–CdS core‐shell modes appear to be well described by the PMA formalism. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Solution properties of triphenylsilyl cellulose

AbstractFive samples of triphenylsilyl cellulose (TPSC) are characterized in solution by osmometry, viscometry, and size exclusion chromatography. The isolated and purified cellulose ethers are prepared in a N,N‐dimethylformamide and pyridine medium under heterogeneous starting conditions and a nitrogen atmosphere by silylation of activated celluloses with triphenylchlorosilane at 115–120°C. TPSCs are characterized by their polydispersities and degrees of substitution by osmometry and viscometry in various solvents. The Mark–Houwink–Sakurada equation coefficients are evaluated in 1,1,1‐trichloroethane, chloroform, and o‐xylene at 30°C and in o‐xylene over a temperature range of 30–70°C. Values of 2.12–2.18 are obtained for exponent a. This indicates, in combination with low values of the preexponential factor (on the order of 10−12), strong stiffness of the macromolecular chains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1257–1261, 2007

Resonant propagation of femtosecond laser pulse in DBASVP molecule: one-dimensional asymmetric organic molecule

We have investigated the resonant propagation of femtosecond laser pulse in 4-trans-[p-(N, N-Di-n-butylamino)-p-stilbenyl vinyl] pyridine medium with permanent dipole moments. The electronic structures and parameters for the compound have been calculated by using density functional theory. In the optical regime, there is one charge-transfer state, and the molecule can thus be simplified as a two-level system. Both the one- and two-photon transitions occur between the ground and charge-transfer states. The numerical results show that the permanent dipole moments have an obvious effect on the propagation of the ultrashort pulse laser. The ideal self-induced transparency disappears for 2 pi pulse, and second harmonic spectral components occur significantly due to the two-photon absorption process. For the 6 pi pulse, continuum frequency generation is produced and a shorter duration pulse in time domain with 465 as is obtained.

Thermolysis of octa (hydridodimethylsiloxyl) octasilsesquioxane in pyridine media and subsequent toluidine blue O adsorption

This work describes the synthesis of octa (hydridodimethylsiloxyl) octasilsesquioxane (Q 8M 8 H) and its thermolysis in pyridine media. The new compound called CPy was characterized by FTIR, NMR–MAS, XRD, MEV spectroscopies and TGA analyses. These results indicate that silsesquioxanes cages (octanion) are maintained after thermal treatment. A cleavage of vertex siloxy groups yielding a nanocomposite with polymeric nature is proposed. Its structure and morphology allows the adsorption/inclusion of electrochemical mediator, toluidine blue O. The square wave voltammetry analysis of resulting composite (CPyTBO) exhibits two redox couple with a formal potential ( E 0′) 0.1 V and 0.26 V to I and II redox couples respectively, (Britton–Robinson (BR) buffer pH 3, ν=10 Hz versus SCE) ascribed to a monomer and dimmer of the toluidine blue species. This paper opens the use of spherosiloxane derived materials as host for small molecules in the electrochemical field.