Reactions of Carbenes with Unsaturated Polymers

Abstract The literature has a limited amount of data on chain reactions of unsaturated polymers, in particular diene polymers. The appearance of a paper dealing with addition of dichlorocarbene to polyisoprene and to polybutadiene has impelled us to publish results of studies we made on reactions of unsaturated polymers with carbenes, which have made it possible for the first time to obtain polymers containing in the main chain, or in the side chains, cyclopropane groups with polar substituents. Addition of carbenes to cis-1, 4-polyisoprene, trans-1, 4-polyisoprene, 1, 4-polybutadiene, and 1, 2-polybutadiene was accomplished through decomposition reactions of diazoacetic esters catalyzed by copper salts (for carbethoxycarbene and carbomethoxycarbene) and the reaction of the ethyl ester of trichloroacetic acid with sodium methylate (for dichlorocarbene).

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Unravelling Main- and Side-Chain Motions in Polymers with NMR Spectroscopy and Relaxometry: The Case of Polyvinyl Butyral

Polymers ◽

10.3390/polym13162686 ◽

2021 ◽

Vol 13 (16) ◽

pp. 2686

Author(s):

Lucia Calucci ◽

Silvia Pizzanelli ◽

Alessandro Mandoli ◽

Artur Birczyński ◽

Zdzisław T. Lalowicz ◽

...

Keyword(s):

Glass Transition ◽

Nmr Spectroscopy ◽

Main Chain ◽

Amorphous Polymer ◽

Polyvinyl Butyral ◽

Side Chains ◽

Nmr Relaxometry ◽

Field Cycling ◽

Nmr Methods ◽

First Time

Polyvinyl butyral (PVB) is an amorphous polymer employed in many technological applications. In order to highlight the relationships between macroscopic properties and dynamics at a microscopic level, motions of the main-chain and of the propyl side-chains were investigated between Tg − 288 °C and Tg + 55 °C, with Tg indicating the glass transition temperature. To this aim, a combination of solid state Nuclear Magnetic Resonance (NMR) methods was applied to two purposely synthesized PVB isotopomers: one fully protonated and the other perdeuterated on the side-chains. 1H time domain NMR and 1H field cycling NMR relaxometry experiments, performed across and above Tg, revealed that the dynamics of the main-chain corresponds to the α-relaxation associated to the glass transition, which was previously characterized by dielectric spectroscopy. A faster secondary relaxation was observed for the first time and ascribed to side-chains. The geometry and rate of motions of the different groups in the side-chains were characterized below Tg by 2H NMR spectroscopy.

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The Total Synthesis of Rhabdastrellic Acid A

10.26434/chemrxiv.7479944 ◽

2018 ◽

Author(s):

Yaroslav Boyko ◽

Christopher Huck ◽

David Sarlah

Keyword(s):

Total Synthesis ◽

Late Stage ◽

Cross Coupling ◽

Side Chains ◽

General Strategy ◽

Modular Approach ◽

Linear Sequence ◽

Generating Sequence ◽

First Time

<div>The first total synthesis of rhabdastrellic acid A, a highly cytotoxic isomalabaricane triterpenoid, has been accomplished in a linear sequence of 14 steps from commercial geranylacetone. The prominently strained <i>trans-syn-trans</i>-perhydrobenz[<i>e</i>]indene core characteristic of the isomalabaricanes is efficiently accessed in a selective manner for the first time through a rapid, complexity-generating sequence incorporating a reductive radical polyene cyclization, an unprecedented oxidative Rautenstrauch cycloisomerization, and umpolung 𝛼-substitution of a <i>p</i>-toluenesulfonylhydrazone with in situ reductive transposition. A late-stage cross-coupling in concert with a modular approach to polyunsaturated side chains renders this a general strategy for the synthesis of numerous family members of these synthetically challenging and hitherto inaccessible marine triterpenoids.</div>

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Synthesis and Molecular Structure of Disulfane

Zeitschrift für Naturforschung B ◽

10.1515/znb-1991-1011 ◽

1991 ◽

Vol 46 (10) ◽

pp. 1338-1342 ◽

Cited By ~ 15

Author(s):

Josef Hahn ◽

Petra Schmidt ◽

Klaus Reinartz ◽

Jörg Behrend ◽

Gisbert Winnewisser ◽

...

Keyword(s):

Molecular Structure ◽

Dihedral Angle ◽

Trichloroacetic Acid ◽

Microwave Spectroscopy ◽

Stabilizing Agent ◽

Rotary Evaporator ◽

First Time

The synthesis and structure of disulfane are presented. Pure disulfane, H2S2, has been obtained by the cracking distillation of raw sulfane mixtures in a rotary evaporator, thus substituting the classical cracking column for the rotating flask of the evaporator. Pure, gaseous dideuterodisulfane could be generated by the solvolysis of bis(methyldiphenylsilyl)disulfane, (MePh2Si)2S2, with D2O in the presence of trichloroacetic acid as stabilizing agent. Partially deuterated disulfane has been prepared by H,D exchange between pure H2S2 and DCl. For the first time the molecular structure of HSSH has been determined based solely on microwave spectroscopy with the following parameters: r(SS) = 2.0564 A, r(SH) = 1.3421 A, dihedral angle γ = 90.34°, and <(SSH) = 97.88°.

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Liquid crystalline main chain polymers with a poly(p-phenylene-terephthalate) backbone: 7. Thermal expansion of oriented films of the polyester with dodecyloxy side chains

Journal of Polymer Science Part B Polymer Physics ◽

10.1002/polb.1994.090320508 ◽

1994 ◽

Vol 32 (5) ◽

pp. 851-857 ◽

Cited By ~ 6

Author(s):

J. A. H. M. Buijs ◽

S. B. Damman

Keyword(s):

Thermal Expansion ◽

Liquid Crystalline ◽

Main Chain ◽

Side Chains ◽

Oriented Films ◽

Main Chain Polymers

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THE ANTIBACTERIAL ACTIVITY OF COMPOUNDS FROM LEAVES OF ARCTOSTAPHYLOS UVA-URS

chemistry of plant raw material ◽

10.14258/jcprm.2018033542 ◽

2018 ◽

pp. 53-60

Author(s):

Владимир (Vladimir) Александрович (Аleksandrovich) Куркин (Kurkin) ◽

Татьяна (Tat'yana) Константиновна (Konstantinovna) Рязанова (Ryazanova) ◽

Александр (Аleksandr) Викторович (Viktorovich) Жестков (Zhestkov) ◽

Артем (Аrtem) Викторович (Viktorovich) Лямин (Lyamin) ◽

Елена (Elena) Владимировна (Vladimirovna) Авдеева (Avdeeva) ◽

...

Keyword(s):

Antibacterial Activity ◽

Ethyl Ester ◽

Uv Spectroscopy ◽

Alcoholic Extract ◽

Gram Positive Bacteria ◽

Chemical Structures ◽

Main Component ◽

First Time ◽

And Staphylococcus Aureus ◽

Perm Region

The aim of this paper is the isolation of individual compounds, which are caused the antibacterial activity of the leaves of the bearberry [Arctostaphylos uva-ursi (L.) Spreng.]. The leaves of Arctostaphylos uva-ursi, collected in Perm region, there were extracted with 70% ethanol, the obtained water-alcoholic infusion there was evaporated in vacuum.By means of the chromatographic methods with the using of silica gel 40/100 and eluent systems (chloroform and ethanol in several ratio) from the evaporated water-alcoholic extract of the leaves of Arctostaphylos uva-ursi, a substance with antibacterial activity, ethyl ester of p-digallic acid, which is a new natural compound, was isolated along with arbutin ((1-О-b-D-glucopyranoside of hydroquinone) from the leaves of this plant. The chemical structures of the ethyl ester of p-digallic acid and arbutin were established with the using of data of 1H-NMR-spectroscopy, UV-spectroscopy and mass-spectrometry..The antibacterial activity of ethyl ester of p-digallic acid against test cultures of gram-positive bacteria Bacillus cereus and Staphylococcus aureus, gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa for the first time was determined. By antibacterial activity, arbutin was inferior not only to ethyl ester of p-digallic acid, but also to decoction from the leaves of the bearberry. Consequently, the ethyl ester of p-digallic acid is one in main component, which is take the contribution in the antibacterial activity of the decoction and other preparations of the leaves of Arctostaphylos uva-ursi.

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