Effect of fusion conditions ofβ-polypropylene on the new crystallization

The new crystallization of -modification of polypropylene (-PP) was studied after melring as a function of the final temperature of fusion (T _F ). The new crystallization, thermal characteristics, polymorphic composition, and structure of recrystallized samples were highly influenced by theT _F level. As a function ofT _F , three characteristic regions were outlined: Region I below the melting point of -modification, region II between the melting points of - and -modifications, and region III above the melting point of -modification. In the vicinity of the melting points of both modifications, two narrow transition regions are observed where the crystallization and structural characteristics changed abruptly withT _F . AtT _F values in region I, recrystallization of -modification proceeded without any change in the modification. IfT _F fell in region II, the sample crystallized newly into -modification. The optically negative -ring-spherulites were replaced by positive microclusters of -modification and a marked structural memory effect was observed. In region III, the above characteristic became invariant withT _F (region of blank melt). These observations may be interpreted by the role of self nuclei.     

“Blue silver”: transformation of clusters and metal coagulation

The formation and transformations of blue silver ( _max 700 nm) during -irradiation of a weakly alkaline (pH 9) aqueous solution containing AgClO₄, polyacrylic acid (PAA), and isopropanol were studied. We believe that blue silver is a linear silver cluster stabilized on a polymeric molecule. During radiation-chemical reduction the cluster is transformed into new clusters ( _max = 365 and 460 nm). When all of the Ag⁺ ions present in the solution have been reduced, clusters coalesce and a new phase,i.e., colloidal silver particles, forms. The mechanism of the radiation-chemical transformations is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–37, January, 1995.     

Kinetics and mechanism of the hydrolysis of sodium carboxymethylcellulose (Na-CMC) by a cellulase complex

TheSomogyi-Nelson colorimetric method is applied in a new manner more suitable for evaluating the kinetics of the enzyme hydrolysis of sodium carboxymethylcellulose (Na-CMC) catalyzed by the cellulase complex. By means of selective inhibition of a chosen enzyme from the cellulase complex it became possible to trace the effect of the other enzymes included in its composition.

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Kinetik und Mechanismus der Hydrolyse von Natriumcarboxymethylcellulose (Na-CMC) durch einen Cellulase-Komplex

Zusammenfassung Die kolorimetrische Methode nachSomogyi undNelson wird nach einem neuen Verfahren zur Verfolgung der Kinetik der hydrolytischen Spaltung von Natriumcarboxymethylcellulose (Na-CMC), katalysiert durch den Cellulase-Komplex, angewandt. Durch selektive Inhibierung eines bestimmten Enzyms des Cellulase-Komplexes kann man die Wirkung der anderen zu seiner gesamten Zusammensetzung gehörenden Enzyme verfolgen.

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Symbols Used E enzyme (E—cellulase;E—exo-cellobiohydrolase;E—-glucosidase) - [E] _w weight concentration of enzymeE - S substrate (Na-CMC—sodium carboxymethylcellulose) - [S]₀ weight concentration of substrateS - I inhibitor (I—lactose;I—calcium chloride;I—condurrite-B-epoxide) - P product (P—oligosaccharides;P—cellobiose;P—D-glucose) - P end product (K , K , K ) - DP degree of polymerization - DS degree of substitution - ES enzyme-substrate complex (E S, E S, E S) - EP enzyme-product complex (E P, E P) - EI enzyme-inhibitor complex (E I, E I, E I) - M _s molecular mass of substrateS - K _s substrate constant (K _s , K _s , K _s ) - K _I inhibitor constant (K _I , K _I , K _I ) - K _m Michaelis-Menten constant - k ₊₁,k ₊₂ (k ₊₂ ,k ₊₂ ,k ₊₂ ) forward rate constants - k _–1 reverse rate constant - ₀ initial rate of reaction - V maximal reaction rate - A change in absorbance - molar absorption coefficient - wavelength Herrn Prof. Dr.Hans Tuppy zum 60. Geburtstag herzlichst gewidmet.     

2,2′-Diphenyl-Δ3,3′-bi-3H-indole-1,1′-dioxide: Molecular interactions and crystal structure

The Dinitrone 2,2-diphenyl-^3,3-bi-3H-indole-1,1-dioxide acts as a demethylating and dehydrogenating agent. The mechanism of interaction of the dinitrone with donors and acceptors does not involve intermediate charge-transfer complexes probably due to a self association between dinitrone molecules (as supported by X-ray determinations). The crystal structure of the dinitrone was obtained by direct methods;a=9.967 (2),b=19.817 (3),c=10.875 (2) Å, =111.2 (2)°, space group P2₁/n. The finalR andR _w were 0.089 and 0.063 for all measured reflexes.

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2,2-Diphenyl-^3,3-bi-3H-indol-1,1-dioxid: Molekulare Wechselwirkungen und Kristallstruktur

Zusammenfassung Das Dinitron 2,2-Diphenyl-^3,3-bi-3H-indol-1,1-dioxid wirkt als Demethylierungs- und Oxydationsmittel. Die Wechselwirkung des Dinitrons mit Elektronen-Acceptoren und Elektronen-Donatoren geht wegen der Selbstassoziation zwischen den Dinitron-Molekülen ohne die dazwischenliegende Bildung eines Charge-Transfer-Komplexes vor sich; das wird auch von Röntgenstrukturuntersuchungen gestützt. Die Kristallstruktur wurde mit direkten Methoden ermittelt:a=9.967 (2),b=19.817 (3),c=10.875 (2) Å; =111.2 (2)°. P2₁/n. Die endgültigen WerteR undR _w waren 0.089 und 0.063 für alle gemessenen Reflexe.

     

Solubility Study of Nimodipine Inclusion Complexation with α- and β-Cyclodextrin and some Substituted Cyclodextrins

The solubility of nimodipine was measured in aqueous solutions of the following cyclodextrins: -cyclodextrin (-CD), hydroxypropyl--CD (HP--CD), -cyclodextrin (-CD), random substituted methyl--CD (M--CD), three hydroxypropyl--CDs (HP--CD) with mutually different average degree of substitution, and hydroxypropyl--cyclodextrin (HP--CD). From the determined linear solubility diagrams the values of the binding constant K₁₁ of the inclusion complexes of nimodipine with the respective CDs were evaluated. The -CDs efficiently solubilized sparingly soluble nimodipine, the highest value of K₁₁ was found for M--CD (1680 M^-1), followed by -CD (550 M^-1) and HP--CDs, where the higher degree of substitution lowered K₁₁. Only slight solubilization of nimodipine was observed in the solutions of the -CDs and HP--CD.     

peri-Naphthylenediamines. 38. Naphthalene and acenaphthene “proton sponges” with +M substituents in ortho positions with respect to peri-dimethylamino groups

Previously unknown 4,5,6,7-tetrakis(dimethylamino)acenaphthene, which is the first acenaphthene derivative containing four vicinal dialkylamino groups, was synthesized based on 5,6-bis(dimethylamino)-4,7-dinitroacenaphthene. The total synthesis of 1,2,7,8-tetrakis(dimethylamino)naphthalene was carried out starting from 3,6-dinitronaphthalic anhydride. Other proton sponges of this type, viz., 1,7,8-tris(dimethylamino)-2-methoxy- and 1,8-bis(dimethylamino)-2,7-dipiperidinonaphthalenes, were prepared by the nucleophilic substitution in 2,7-dimethoxy-1,8-dinitronaphthalene. In solutions, 1,2,7,8-tetrakis(dimethylamino)naphthalene and its analogs can form di- and trications in the presence of acids. The basicity constants pK _a ¹ of the compounds measured in DMSO depend in a complex way on their structures but correlate with the basicity index B, which is determined by changes in the chemical shifts _H after the addition of the first proton. Due to low C-nucleophilicity of ortho-disubstituted proton sponges in combination with high basicity, these compounds hold considerable promise as reagents in organic synthesis.     

“Crowns”, and aromatic sextets in primitive coronoid hydrocarbons

Summary A type of graphs derived from a cycle and associated with primitive coronoids are referred to as crowns. The characteristic polynomials and matching polynomials of crowns are studied. These notions are used to calculate the sextet polynomial for primitive coronoids. Patterns of aromatic sextets are treated in some detail.

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Crowns und aromatische Sextette in einfachen coronoiden Kohlenwasserstoffen

Zusammenfassung Eine Graphentype, die von einem Cyclus abgeleitet ist und mit einfachen Coronoiden verknüpft ist, wird als Crown bezeichnet. Die charakteristischen Polynome und die matching Polynome der Crowns werden untersucht. In diesem Rahmen werden die Sextett-Polynome für einfache Coronoide berechnet. Die Muster der aromatischen Sextette werden im Detail behandelt.

     

Inclusion of Ring A of Cholesterol Inside the β-Cyclodextrin Cavity: Evidence from Oxidation Reactions and Structural Studies

The disposition of cholesterol inside the -cyclodextrin cavity(-CD) was deduced from oxidation of cholesterol secondary alcoholgroups by Ca(OCl)₂ and H₂O₂ in thepyridine–acetic acid system. The amount of cholest-4-ene-3-one formedwas found to be proportional to the concentration of -cyclodextrin,resulting in 56.1% of ketone. The oxidation rate was enhanced by-cyclodextrin and its methyl, polymer and 1 : 1copper(II)–-cyclodextrin derivatives. Detailed investigationsinvolving UV-visible, ¹³C- and ¹H-NMR(T₁, 1D NOE and ROESY) spectroscopic studies were carried out.A binding constant value of 15,385 ± 1500 M^-2 wasobtained for the 2 : 1heptakis-2,6-di-O-methyl--cyclodextrin(DM-CD) : cholesterolcomplex in chloroform from UV studies. Proton and solid state¹³C-CP MAS spectra of the -CD–cholesterol mixtureshowed large magnitude shifts for the protons from the wider end of the-CD cavity as well as those of ring A and ring B of cholesterol. Both1D NOE and ROESY measurements indicated the proximity between ring A andring B protons of cholesterol and the wider end protons of -CD andDM-CD. Besides, analysis of _c,_i and tau;_m from T₁measurements showed not only a lowering of rotational motions but a value of 0.016–0.048 for some of the cholesterol protons, typical of aweak complex. Based on these studies, a probable structure for the 2 : 1complex involving two molecules of -CD/DM-CD was proposed withportions of ring A and ring B being present inside the wider end of the-CD/DM-CD cavity and ring D and the side chain attached atposition 17, projecting into the wider end of the secondCD/DM-CD molecule.     

O-Heterocycles by the cyclization of side-chain bromomethoxylated 2′-acetoxychalcones

Summary The title chalcone derivatives react with aqueous sodium hydroxide of various concentrations to form aurones as the major product, together with small amounts of flavones. However, the introduction of 4-nitro or 4-chloro substituents resulted in the formation of flavones as the major product.

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O-Heterocyclen mittels Cyclisierung von an der Seitenkette brommethoxylierten 2-Acetoxychalconen

Zusammenfassung Die im Titel genannten Chalconderivate reagieren mit Natronlauge in verschiedenen Konzentrationen, wobei Aurone zusammen mit geringen Mengen an Flavonen entstehen. Die Einführung von 4-Nitro- oder 4-Chlor-Substituenten führte jedoch zur bevorzugten Bildung von Flavonen.

     

Sulfur heterocycles. 13. Oxidative chlorination of β-thiolactones. A novel synthesis of β-(chlorosulfinyl)alkanoyl chlorides and 1,2-oxathiolan-5-one 2-oxides

Chlorination of -thiolactones with chlorine or sulfuryl chloride in acetic anhydride at a reactant ratio (RR) of 1:2:1 gives -(chlorosulfinyl)alkanoyl chlorides in 75–89% yields. Oxidative chlorination of -thiolactones with RR of 1:3:2 affords -(chlorosulfinyl)alkanoyl chlorides and cyclic sulfinic anhydrides (1,2-oxathiolan-5-one 2-oxides). The optimum RR for the preparation of 1,2-oxathiolan-5-one 2-oxides is 1:2:2. Hydrolysis of -chloro--(chlorosulfinyl)carbonyl chlorides has given novel -chlorinated sulfinocarboxylic acids.For communication 12, see [1].A. N. Nesmeyanov Institute of Heteroorganic Chemistry, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2153–2158, September, 1992.     

‘Hairdressing’ Shish-kebabs by melting

Summary A previous paper established the principle of hairdressing showing that polyethylene shish-kebab fibres can be reversibly transformed by appropriate preparation conditions between three morphologies, smooth fibres; fibres with closely spaced lamellar overgrowths; fibres with widely spaced lamellar overgrowths, where the spacing is sensitively affected by storage temperature (3). In the present paper this hairdressing work is extended to include the molten state. Three classes of morphology analogous to the three obtained from solution (although with certain minor differences) can be obtained by melting shish-kebabs at constant length, followed by quenching or isothermal crystallization. These melt-hairdressed fibres can be transformed back into shish-kebabs of typical solvent hairdressed appearance by the previously established procedures for solvent hairdressing. Thus all these works, following on from the trend established by Pennings (4), serve to highlight the fact thatall shish-kebabs acquire their external morphology at temperatures which are beneath those of the core formation during final cooling or storage and thatall external forms associated with a given core are interconvertible. On the molecular level these features highlight the intrinsically hairy nature of the core fibre as formed.With 5 figures     

Enumeration of Kekulé structures for some coronoid hydrocarbons: “Waffles”

Summary Primitive coronoids of hexagonal symmetry (D _6h orC _6h ) are referred to as waffles. Some theorems about unbranched catacondensed benzenoids are presented and used to derive a general combinatorial formula for the number of Kekulé structures (K) for waffles. The symmetry-adapted method of fragmentation is employed. SeveralK formulas for special classes of waffles are also reported.

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Die Anzahl von Kekulé-Strukturen für einige aromatische Coronoid-Kohlenwasserstoffe: Waffel-Strukturen

Zusammenfassung Einfache Coronoide von hexagonaler Symmetrie (D _6h oderC ₆ h) werden als Waffel bezeichnet. Einige Theoreme bezüglich unverzweigter catakondensierter Benzenoide werden angegeben und zur Ableitung einer generellen Formel für die Anzahl von Kekulé-Strukturen (K) für Waffel benutzt. Es wird die symmetrie-adaptierte Methode zur Fragmentierung angewendet. Außerdem werden einigeK-Formeln für spezielle Klassen von Waffeln angegeben.

     

Synthesis of β‐Chlorinated Macrocyclic [Au(C14H20N4Cl2)]X (X = AuCl2, ClO4, AuCl4) Gold(III) Complexes. Crystal and Molecular Structures of [Au(C14H20N4Cl2)]ClO4

A squareplanar [AuL₂]⁺ gold(III) complex [L₂ = 6.13dichloro5,7,12,14tetramethyl1,4,8,11tetraaza4,6,11,13tetraenato(2-)] containing two chlorine atoms in the position of the ligand hexacyclic ring was first synthesized by the reaction of the [AuL₁]⁺ tetraiminate complex [L₁ = 5,7,12,14tetramethyl1,4,8,11tetraaza4,6,11,13tetraenato(2-)] with HAuCl₄ in an acetone – DMFA solution. The complex was isolated in the form of dichloroaurite (I), perchlorate (II), and tetrachloroaurate (III). Compounds I–III were studied by elemental and Xray diffraction analyses and IR and NMR spectroscopies. Single crystals of [AuL₂]ClO₄ were obtained, and the crystal structure of this compound was determined from Xray diffraction patterns. The crystals are monoclinic: a = 10.147(2), b = 7.260(1), c = 12.519(2), = 96.70(1)°, V = 915.9(3)³, Z = 2, space group P2/c, d_calc = 2.218, d_meas = 2.209 g/cm³ The crystal structure is built of nearly planar [Au(C₁₄H₂₀N₄Cl₂)]⁺ cations and [ClO₄]^- anions. Introduction of chlorine atoms into the positions of the hexacyclic rings of the tetraazamacrocycle hardly changes the lengths of the delocalized C N and C C bonds.     

Simulation of the molecular and electronic structure of C60 fullerene π-complex with twelve half-sandwich species FeC5H5

The problem of existence of ⁵--complexes of fullerenes and their derivatives is discussed. The stability of the ⁵--complex C₆₀(FeCp)₁₂ (viz., icosahedral C₆₀ fullerene coated with twelve FeCp groups, each coordinated to its own pentagonal face of the fullerene cage) was first estimated in the framework of density functional approach (PBE approximation). The molecular and electronic structure of a biradical complex of C₆₀ fullerene with ten FeCp groups, C₆₀(FeCp)₁₀ (D _5d symmetry), and a 2⁵--complex of substituted fullerene H₁₀C₆₀, H₁₀C₆₀(FeCp)₂ (D _5d symmetry) in which hydrogen atoms are attached to the C atoms in the -positions relative to the atoms of the polar five-membered cycles, was simulated. According to calculations, the coated complex, I _h-C₆₀(FeCp)₁₂, should be much more stable than the complex of naked fullerene with one or two polarly located FeCp groups and only slightly less stable than the ferrocene molecule FeCp₂. The existence of C₆₀(FeCp)₁₂ and H₁₀C₆₀(FeCp)₂ complexes was suggested.     

Bromination of polyfluorinated α,β-enones

Polyfluoroalkyl-,-enones readily add Br₂ to give ,ß-dibromoketones. The latter are readily and regioselectively dehydrobrominated to -bromo-,-enones on treatment with K₂CO₃ or NEt₃ Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2134–2136, December, 1993.     

Reaction characteristics of cellulose in the LiCl/1,3‐dimethyl‐2‐imidazolidinone solvent system

In order to elucidate the nature of the LiCl/1,3dimethy2imidazolidinone (DMI) solvent system as one of the homogeneous reaction media of cellulose, cellulose acetate (CA) and Omethylcellulose (MC) were prepared using this solvent system, and the distribution of substituents within anhydroglucose units was examined by ¹³CNMR. It was found that (i) homogeneous cellulose solutions can be easily prepared by heating 2, 5–12 and 100 parts of weight of cellulose, LiCl, and DMI, respectively, and (ii) the relative reactivity of hydroxyl groups is in the order C6 > C2 > C3 for both CA and MC. A remarkable feature of this solvent system is that the reaction efficiency in etherification is very high compared with other homogeneous solvent systems.     

A new detection method for purines in thin-layer chromatography

Summary The separation of some purines by thin-layer chromatography, utilizing precoated plates with Silicagel R as stationary phase and the following mobile phases: i-butanol: methylethylketone: ammonium hydroxide 25%: water (40252015) and n-propanol: ammonium hydroxide 25%: water (80155) is reported.Visualisation of the spots has been achieved by spraying with aqueous 1% uranyl acetate and irradiating with UV both at 254 and 366 nm. The visual detection of a spot was 0.01 g.     

Reaction of aminals of conjugated unsaturated ω-dimethylaminoaldehydes with 1,2-, 1,3-, 1,4-, 1,5-, and 1,6-diketones

The condensation of aminals of -dimethylaminoacrolein and 5-dimethylaminopenta-2,4-dienal with cyclic and acyclic 1,2-, 1,3-, 1,4-, 1,5-, and 1,6-diketones was studied. A series of previously unknown bis(,-dimethylaminopolyenyl)diketones was synthesized; their structures were established by means of¹H and¹³C NMR spectroscopies. The electron absorption spectra were employed to study the mutual influence of -aminopolyene chromophores separated by two C=O groups.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1235–1241, July, 1993.     

Ab initio SCF and CI study of the electronic spectrum of pyridine N-oxide

Configuration interaction (CI) studies of ground, n *, * * electronically excited states are reported for pyridine N-oxide. The transition energy to the lowest * excited ¹ B ₂ state is calculated at 4.35 eV, compared to the experimental spectrum range of 3.67–4.0 eV. This state lies below the lowest n * excited ¹ A ₂ state calculated at 4.81 eV above the ground state. The only experimentally reported triplet state at 2.92 eV above the ground state is predicted to be the ³ A ₁ (*) state. The calculated energy lies at 3.27 eV. Numerous other high-lying singlet states as well as the triplet states have also been calculated. The intramolecular charge transfer character of the ground and the excited states have been studied in terms of the calculated dipole moment and other physical properties.