نتایج جستجو برای: polyenes

تعداد نتایج: 951  

Journal: :Chemical and Pharmaceutical Bulletin 1968

Avat (Arman) Taherpour Fatemeh Shafiei

The alternative double bonds and conjugation in the polyene compounds are one of the main properties in these compounds. Each carbon-carbon bonds in a polyene compound along the chain has appreciable double-bond character. The p-electrons are therefore not localized but are relatively free to move throughout the entire carbon skeleton as an one-dimensional box. The skeleton be considered as a r...

1997
Jerry Ray Dias

The analysis of π-electronic structure of polymer networks continues to attract the interest of theoretical1 and synthetic2-7 researchers. One of the major objectives of these studies is to gain insight on the design of potential organic conductors and ferromagnets. Extended pπ-conjugated systems represent the simplest models for molecular wires. The reduction of the HOMO-LUMO bandgap in conjug...

Journal: :Journal of the American Chemical Society 2002
Dean J Tantillo Roald Hoffmann

We report calculations on the activation barriers for antarafacial [1,7]-hydrogen shifts in various helical polyenes containing saturated substructures. Based on these calculations, we predict that the barrier for analogous hydrogen shifts in the infinite system-a [1,7]-shiftamer-is only approximately 14 kcal/mol if the reactant is preorganized in an appropriate helical conformation.

2013
Michael C. Böhm

für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namen...

2007
S. M. MAKIN M. V. Lomonosov

Convenient methods for the preparation of 1-alkoxydienes are reviewed. It is shown that 1-alkoxydienes are very reactive and can be successfully used for the synthesis of polyene compounds. These include some important natural products, such as polyene aldehydes, vitamin A aldehyde, the ethers and esters of vitamin A, f3-ionolidenacetaldehyde, f3-C,9-aldehyde and other related compounds. A conv...

2000
Gerard Hornstra

Essential fatty acids (EFAs) and their long-chain polyenes (LCPs) are indispensable for human development and health. Because humans cannot synthesize EFAs and can only ineffectively synthesize LCPs, EFAs need to be consumed as part of the diet. Consequently, the polyunsaturated fatty acid (PUFA) status of the developing fetus depends on that of its mother, as confirmed by the positive relation...

2001
Richard Francis Langler

A simple set of trimethylene-substituted even, fully-π-bonded, non-alternant monocycles is shown to have several key features in common with acyclic, even alternant polyenes at the Hückel level. These non-alternant molecules provide a bridge between alternant and non-alternant hydrocarbons. This topic might serve as a useful addition to Hückel theory courses targeted at senior undergraduate stu...

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