Synthesis and characterization of α,ω-dichloro-polymethylphenylsilane

The synthesis of a functional polysilane, α,ω-dichloro-polymethylphenylsilane (α,ω-dichloro-PMPS), based on the Wurtz-type reductive coupling, has been considered. A study of some reaction parameters shows that both yield and molecular weight distribution of α,ω-dichloro-PMPS can be greatly influenced by the work-up conditions, reaction time, monomer concentration and temperature during the initiation of the polymerization. By varying the synthesis conditions, different ratios of high and low molecular weight fractions were obtained. Samples of different molecular weight were isolated by fractional precipitation of the crude polymers. The chlorine-end functionalization was confirmed by ²⁹Si NMR spectroscopy and the concentration of end-groups was quantitatively determined by elemental analysis of chlorine.     

Combined study of vibrational spectra of α-carboline by theoretical and experimental IR methods

This paper reports the application of a scaled ab initio density-functional theory (DFT) at B3LYP/ccpvtz level to calculate the vibrational spectrum of α-carboline (9H-pyrido[2,3-b]indole), αCB, as well as the comparison of theoretical results with the experimental spectra. They have been recorded in Cl₃CD solution and in solid KBr pellets in the 4000-700 cm⁻¹ range. To test the adequacy of the computational method to reproduce the experimental vibrational spectra of αCB, this computational method has also been applied to the related and simpler molecules indole, Ind, and α-azaindole, αAInd. Previously reported assignments for the last compounds have been taken as reference for the subsequent assignments of the αCB vibrational bands. The results show that the hydrogen bonding interactions mainly affect the high frequency region while the skeletal vibration region keeps rather unchanged with the physical state of the sample. Moreover, apart from the vibrations involving the whole carboline nucleus, most of the experimental bands retain their original Ind and/or αAInd frequencies, thus allowing an easy assignment of the computed modes to the αCB vibrational bands.     

Polyesters by lipase-catalyzed polycondensation of unsaturated and epoxidized long-chain α,ω-dicarboxylic acid methyl esters with diols

Long-chain, symmetrically unsaturated α,ω-dicarboxylic acid methyl esters (C₁₈, C₂₀, C₂₆) were obtained by the catalytic metathetical condensation of 9-decenoic, 10-undecenoic, and 13-tetradecenoic acid methyl esters, respectively, with the homogeneous Grubbs catalyst bis(tricyclohexyl phosphine) benzylidene ruthenium dichloride dissolved in methylene chloride. The dicarboxylic acid esters were epoxidized chemoenzymatically with H₂O₂/methyl acetate with Novozym 435^®, an immobilized lipase B from Candida antarctica. Polyesters from symmetrically unsaturated or epoxidized α,ω-dicarboxylic acid methyl esters with 1,3-propanediol or 1,4-butanediol, respectively, were achieved by enzymatic polycondensation with the same biocatalyst applied. With 1,3-propanediol as a substrate, the linear unsaturated and epoxidized polyesters had molecular weights of 1950–3300 g/mol and melting points of 47–75 °C, whereas with 1,4-butanediol as a substrate, the resulting polyesters showed higher molecular weights, 7900–11,600 g/mol, with similar melting points of 55–74 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1601–1609, 2001     

Vibrational spectra of α-glucose, β-glucose, and sucrose: anharmonic calculations and experiment

The anharmonic vibrational spectra of α-D-glucose, β-D-glucose, and sucrose are computed by the vibrational self-consistent field (VSCF) method, using potential energy surfaces from electronic structure theory, for the lowest energy conformers that correspond to the gas phase and to the crystalline phase, respectively. The results are compared with ultraviolet-infrared (UV-IR) spectra of phenyl β-D-glucopyranoside in a molecular beam, with literature results for sugars in matrices and with new experimental data for the crystalline state. Car-Parrinello dynamics simulations are also used to study temperature effects on the spectra of α-D-glucose and β-D-glucose and to predict their vibrational spectra at 50, 150, and 300 K. The effects of temperature on the spectral features are analyzed and compared with results of the VSCF calculations conducted at 0 K. The main results include: (i) new potential surfaces, constructed from Hartree-Fock, adjusted to fit harmonic frequencies from M?ller-Plesset (MP2) calculations, that give very good agreement with gas phase, matrix, and solid state spectra; (ii) computed infrared spectra of the crystalline solid of α-glucose, which are substantially improved by including mimic groups that represent the effect of the solid environment on the sugar; and (iii) identification of a small number of combination-mode transitions, which are predicted to be strong enough for experimental observation. The results are used to assess the role of anharmonic effects in the spectra of the sugars in isolation and in the solid state and to discuss the spectroscopic accuracy of potentials from different electronic structure methods.     

Synthesis and structural study of α-amino- and α,ω-diamino oligoamides-11

α-Amino (MAO) and α,ω-diamino (DAO) oligoamides were prepared using dodecylamine or 1,6 diaminohexane as a chain limitator. These were characterized by GPC, ¹H-NMR and ¹³C-NMR; molecular models: N-dodecyldodecanamide and 1,6 bis dodecylaminohexane; trifluoroacetylation was used to dissolve the oligoamides. DAO prepared in the melt contains two types of chains, depending on the position of the limitator. When oligomers were prepared in solution using the Yamazaki method, the presence of residual phosphorus derivatives in the oligoamides could not be avoided.     

Synthesis of symmetrical acetylenic hydrocarbons and their α,ω-di-derivatives from α,α,α-trichloro- and α,α,α,ω-tetrachloro-alkanes

Summary By the action of sodium in xylene on polychloro hydrocarbons containing -CCl₂-CCl₂- or- CC1=CC1-, groupings the corresponding symmetrical acetylenic hydrocarbons containing 10,14, and 18 carbon atoms in the molecule were obtained. From ,-disubstituted tetrachloroalkanes by the same method 1,10-diethoxy-5-decyne, 1,14-diethoxy-7-tetradecyne, and 1,14-bisdiethylamino-7-tetradecyne were obtained.The spectra were determined in the Optical Laboratory of the Institute of Heteroorganic Compounds of the USSR by N. A. Chumaevskii, who we thank.     

New α,ω-diamido and α,ω-diamino mono-and bi-bridged acridine dimers

A novel set of dimers derived from 9-amino acridine was prepared and characterized by¹H and¹³CNMR. These derivatives are bridged at several different positions of the heterocyclic moieties, by the way of ,-diamido or ,-diamino side-chains. Additionally the preparation of some bi-bridged compounds was achieved.

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Neue ,-Dimaido- und ,-Diamino-Mono- und Bi-überbrückte Acridin-Dimere

Zusammenfassung Es wurde eine neue Reihe von Dimeren des 9-Aminoacridins hergestellt und mittels¹H und¹³C-NMR charakterisiert. Diese Derivate sind an verschiedenen Positionen des Heterocyclus mit ,-Diamido- oder ,-Diamino-Seitenketten überbrückt. Zusätzlich wurden auch einige zweifachüberbrückte Verbindungen hergestellt.

     

Synthesis and characterization of α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxanes

A series of α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxanes with different molecular weight were synthesized. The preparation included five steps which were hydroxyl protection, alkylation, anionic ring-opening polymerization, hydrosilylation and deprotection. The structure of reaction products was characterized by FT-IR, GC, 1H NMR. 2007 Qing Si Zhang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Synthesis,Transport, and Ionophoric Properties of α,ω-Biphosphorylated Azapodands: X. Membrane Transport of Organic Acids by Phosphorylated α,ω-Diazapodands

The membrane transport properties of novel phosphorylated azapodands with respect to mono- and polyfunctional carboxylic acids were studied. The structures of the transported Н-complexes are discussed, the complexing centers in the carriers are considered, and the correlations between the structure and transmembrane transport efficiency of the acid substrates are demonstrated.     

Synthesis and Characterization of Monodisperse α,ω-Divinylpolydimethylsiloxane and ω-Vinylpolydimethylsiloxane

Abstract

ω-Vinylpolydimethylsiloxanes (ω-PDMS) and α,ω-divynilpolydimethylsiloxanes (α,ω-PDMS) have been synthesized by anionic polymerization of hexamethylcyclotrisiloxane (D3). The reactions were carried out in n-hexane and tetrahydrofuran (THF), respectively. The initiator was n-butyl-lithium (n-BuLi); tetrahydrofuran was used as an electron donor compound to promote the polymerization of D3. The synthesized polymers have been characterized by infrared (FTIR), proton nuclear magnetic resonance spectroscopy (NMR), light scattering (LALLS), and gel permeation chromatography (GPC). Molecular weights ranging from 20,000 to 100,000 were obtained with relatively narrow molecular weight distributions; Mw/Mn < 1.25.     

Study of the temperature effect on IR spectra of crystalline amino acids,dipeptids, and polyamino acids. III. α-Glycylglycine

The IR spectra of α-glycylglycine (H₃ ⁺N-CH₂-CO-NH-CH₂-COO^?) are studied in the temperature range of 93 to 413 K. Changes in the spectra due to temperature variation are correlated with the previously obtained X-ray diffraction data on anisotropic compression of the structure and changes in the parameters of hydrogen bonding. Changes in the vibrational frequencies of NH ₃ ⁺ and COO groups in the IR spectrum of α-glycylglycine are compared to changes in the vibrational frequencies of the same groups in the IR spectra of polymorphs of glycine, L- and DL-serine.     

Electrochemical oxidation of tetramethyl esters of α,α,ω,ω-alcaneteracarboxylic acids

Cyclization of esters of butane-1,1,4,4- and pentane-1,1,5,5-tetracarboxylic acids during electrolysis in methanol in the presence of Nal produces, with a yield of 95%, the esters of cyclobutane-1,1,2,2- and cyclopentane-1,1,2,2-tetracarboxylic acids. Under similar conditions, esters of the highest ,,,-alkanetetracarboxylic acids undergo iodation and hydroxymethylation due to electrical oxidation of methanol to formaldehyde. During electrolysis in methanol in the presence of NaOAc, the esters of ,,,-alkanetetracarboxylic acids undergo effective hydroxymethylation, followed by cyclization into substituted five- and six-member lactones, or tetrahydrofurans when structurally possible.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2332–2339, October, 1992.