Polyacetylenes aliphatic

An interesting example of regioselective CM with ethylene as a tool in natural product degradation was recently disclosed by Hawaiian authors [149]. Thus, CM using catalyst C and ethylene gas was used to degrade the plant polyacetylene oxylipin (+)-falcarindiol (342) with uncertain stereochemistry at C3. As the reaction provided a meso product (343) in 81% yield by regioselective attack at the aliphatic side chain, the natural compound 342, isolated from a Hawaiian endemic plant, had the 3R,8S configuration shown in Scheme 66. 

A new class of mesogen consisting of polyacetylene derivatives, (II), containing aliphatic spacers was prepared by et al. Tang (3), which had high solvent solubility, moderate melting points, and excellent tractability. 

Several scientific studies provide evidence of the traditional use of parsley in medicine. Food plants of the Apiaceae plant family such as parsley, carrots and celery contain a group of bioactive aliphatic C17-polyacety-lenes, which were shown to be highly toxic towards fungi, bacteria and mammalian cells and to display neurotoxic, anti-inflammatory and antiplatelet aggregatory effects and to be responsible for allergic skin reactions in a study by Christensen and Brandt (2006). The effect of these polyacetylenes towards human cancer cells, their human bioavailability and their ability to reduce tumour formation in a mammalian in vivo model indicate that they may be beneficial for health. 

Many substituted polyacetylenes (e.g., all the polymers in Table 25) are completely soluble in low-polarity solvents such as toluene and chloroform. Their solubility can be attributed to the presence of substituents and their amorphous structure. When inspected in more detail, aliphatic and silicon-containing polyacetylenes are soluble in aliphatic solvents such as hexane but insoluble in 1,2-dichloroethane, whereas aromatic polyacetylenes show the opposite solubility property. 

Photoresists and electron-beam resists play an important role in the manufacture of very large-scale integrated circuits 116). Owing to the following radiation-degradable behavior, aliphatic polyacetylenes might become a new material applicable to electron-beam resists. 

All the experimental results for alkali and alkaline-earth metals can be interpreted by considering that soot precursors P (e.g., polyacetylenes in the combustion of aliphatic hydrocarbons (10)) are both oxidized by OH radicals with the rate Vi and are turned into small soot particles with the rate V2. Depending on the kind of metal and the experimental conditions, one or the other of these reactions will be promoted, with the rates becoming Vi and V2, respectively. 

Zdero . Recently discovered natural acetylenes appear in the Chemical Society Specialist Reports on Aliphatic Chemistry for the years 1972 and 1973 and will presumably figure in future editions. The prc-1966 era of natural acetylene chemistry is covered comprehensively by tsvo reviews in German and the pre-1964 period in a review in English. A number of shorter articles have also appeared, one recently covering exclusively the non-polyacetylenic acetylenes . A table of fungal polyacetylenes is also available . 

An example of an enantiomerically pure polymer is also shown [11]. Aoki et al. showed that films of a polyacetylene substituted with a (-)-p-pinene derivative formed an effective membrane for chromatographic resolutions of racemic mixtures. ( )-2-Butanol was resolved to 29.8% eje. and unsaturated polymers for both liquid-phase and gas-phase separation applications (8, 9, 79]. It has been suggested that the rigidity and irregularity of the highly substituted polyacetylene chain, combined with the presence of aliphatic substituents which reduce interchain interactions, are important for the polymers transport properties [10]. 

Most substituted polyacetylenes obtained with group 5 and 6 transition-metal catalysts are soluble in common organic solvents with relatively low polarities such as toluene, chloroform, and tetrahydrofuran (Table 11). Aliphatic polyacetylenes are also soluble in... 

While polyacetylene is an electrical semiconductor, substituted polyacetylenes are virtually insulators (Table 13). Among them, the aliphatic polymers possess specific conductivities as low as 10 S cm" while aromatic monosubstituted acetylene polymers have values in the order of ca 10 S cm"h The low conductivities of substituted polyacetylenes are attributable to their twisted main-chain conformation induced by the bulky substituents. The unpaired-electron densities of most disubstituted acetylene polymers are below a detection limit of 1 x 10 spin In contrast, poly(phenylacetylene)... 

B.A. San Jose, S. Matsushita, K. Akagi, Lyotropic chiral nematic liquid crystalline aliphatic conjugated polymers based on di-substituted polyacetylene derivatives that exhibit high dissymmetry factors in circularly polarized luminescence. J. Am. Chem. Soc. 134, 19795-19807 (2012)... 

Mitsuyama, M. and K. Kondo. 2001. Induced chiral helical effect on the main chain of aliphatic polyacetylenes. / Polym Sci Polym Chem 39 913. 

After the earlier examples of single-handed polyacetylenes including 162-165 were reported, " various types of polyacetylenes bearing chiral side groups have been synthesized from phenylacetylene derivatives,propiolic esters, propargyl esters, N-propargylamides, and aliphatic acetylenes. Two examples are introduced here. 

With regards to the mechanical properties of substituted polyacetylenes, aromatic polymers like poly(diphenylacetylene) derivatives are generally hard and brittle, whereas aliphatic polymers with long alkyl chains like poly(2-octyne) are soft and ductile.Considerations of mechanical properties are especially important when polymer membranes or fibers are required for the specific application. 

This volume covers the area of Aliphatic Chemistry for the period January -December 1972 and its overall structure is as in Part I of Volume 1. Drs. R. S. Atkinson and E. W. Colvin have again written the chapters on Functional Group Chemistry with an eye to providing a General Methods report, and Dr. G. Pattenden surveys in two chapters naturally-occurring polyolefinic and polyacetylenic compounds and the burgeoning area of prostaglandin chemistry. 

More than 700 polyacetylene compounds have been characterized from plants, which are mainly prominent in the Asteraceae, Apiaceae and Campanulaceae including many medicinal plants from various parts of the world (Hudson 1989). Food plants of the Apiaceae plant family such as carrots, celery, parsley, fennel and parsnip contain a group of bioactive aliphatic C17-polyacetylenes including falcarinol, falcarindiol, panaxydiol, and polyacetylene 8-0-methylfalcarindiol (Zidom et al. 2005 Christensen and Brandt 2006). 

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