Search results for "TRIPLE"
showing 10 items of 506 documents
Polymerization of mono- and multilayer forming diacetylenes
1977
Heptadeca-2,4-diine-1-ol and Heptadeca-2,4-diine-1-acid were synthesized and their polymerization behaviour in the solid state was investigated. Both compounds polymerize thermally below the melting point and photochemically under the action of uv-light to form polymers via 1,4-addition to the conjugated triple bonds with a backbone of conjugated double-and triple-bonds. The photoresponse spectra resemble the absorption spectra exhibiting maxima of photoreactivity in the absorption band of the conjugated triple bonds of the monomers.
Some monomers, oligomers and polymers with conjugated triple bonds
1991
In the first part new monoaminodiacetylenes with different numbers of CH2-groups, the formation of Perowskit-type Mn complexes and their polymerizability are described. Symmetrical diaminodiacetylenes and some derivatives therefrom have also been prepared. The second part deals with different types of polymers with diacetylene units in the backbone. Under irradiation color formation and crosslinking take place. Well-defined low molecular weight model compounds of polydiacetylenes is the subject of the third part. Finally rod-like but soluble polymers with alternating p-phenylene and acetylene units are described.
Chiral synthetic pseudopeptidic derivatives as triplet excited state quenchers
2009
The behavior of 6 pseudopeptidic models, synthesized by connecting different protected amino acids (Trp, Tyr, Phe, and Lys) with various diamino spacers, as quenchers of the triplet excited state of tiaprofenic acid (and its methyl ester), has been investigated. A series of quenching constants have been determined, which depend on the nature of the quencher and on the stereochemistry of the excited drug. A significant degree of stereodifferentiation has been found for the peptidomimetic synthesized with Phe and Tyr linked by a piperazine bridge. The obtained results support the utility of laser flash photolysis (LFP) as a tool to investigate the interactions between photoexcited drugs and s…
ChemInform Abstract: trans- and cis-Bicyclo(n.1.0)alk-2-ynes of Medium Ring Size.
2010
Starting from cycloalkenes, the cis- or trans-cyclopropano anellated cycloalkynes 2–7 of medium ring size were synthesized. The triple bonds were introduced in the final reaction step either by the fragmentation of the corresponding 1,2,3-selenadiazoles or by direct dehydration of a ketone (Scheme 2). The cis-fused bicycles 2 and 3 and the trans-fused bicycles 5, 6 and 7 could be isolated in a pure state. The intermediary existence of the most strained system trans-bicyclo[7.1.0]dec-2-yne (4) was proven by trapping reactions.
trans- andcis-Bicyclo[n.1.0]alk-2-ynes of Medium Ring Size
1997
Starting from cycloalkenes, the cis- or trans-cyclopropano anellated cycloalkynes 2–7 of medium ring size were synthesized. The triple bonds were introduced in the final reaction step either by the fragmentation of the corresponding 1,2,3-selenadiazoles or by direct dehydration of a ketone (Scheme 2). The cis-fused bicycles 2 and 3 and the trans-fused bicycles 5, 6 and 7 could be isolated in a pure state. The intermediary existence of the most strained system trans-bicyclo[7.1.0]dec-2-yne (4) was proven by trapping reactions.
Push-Pull Oligomers with 2,2-Dicyanovinyl Groups as Electron Acceptors
2007
Three conjugated oligomer series with terminal donor–acceptor substitution were studied: oligo(1,4-phenylenevinylene)s DAOPVs 4a–d (n = 1–4), oligo(1,4-phenyleneethynylene)s DAOPEs 6a–d (n = 1–4) and oligo(2,5-thienyleneethynylene)s DAOTEs 8a–e (n = 1–5). Dialkylamino or methoxy groups served as electron donors and 2,2-dicyanovinyl groups as strong electron acceptors. The push-pull effect polarizes the molecular chains – an effect which is documented by the splitting of the 13C chemical shifts of two carbon atoms of the double or triple bonds in the chain. For higher oligomers (n ≥ 3), the effect is mainly localized at the chain ends. The long-wavelength absorption results in a charge-trans…
Toward Understanding the Photochemistry of Photoactive Yellow Protein: A CASPT2/CASSCF and Quantum Theory of Atoms in Molecules Combined Study of a M…
2009
Photochemical processes that take place in biological molecules have become an increasingly important research topic for both experimentalists and theoreticians. In this work, we report the reaction mechanism of a model of the photoactive yellow protein (PYP) chromophore in vacuo. The results obtained here, using a strategy based on the simultaneous use of the minimum energy path concept and the quantum theory of atoms in molecules applied to this excited state process, suggest a possible way in which the protein could increase the efficiency of the reaction. The role played by other electronic states of the same and different spin multiplicities in the reaction process is also analyzed, wi…
In vivo digestibility and nutritive value of Atriplex halimus alone and mixed with wheat straw
2002
In vivo digestibility trials were carried out using six young rams fed with Atriplex halimus biomass harvested in summer (A) and in early autumn (B), and with a mixture of mid-autumn Atriplex halimus and wheat straw (5[ratio ]1 ratio on fresh matter basis) (C). Atriplex halimus had a high protein content (139·0, 135·9 and 193·4 g/kg DM in A, B and C respectively), but was rich in sodium chloride, especially in summer (145·9 g/kg DM), limiting its use as feed. The summer forage had a higher organic matter (OM) digestibility coefficient than the autumn forage (0·663 v. 0·530) but lower digestible OM intake (16·8 v. 29·4 g/day per kg BW0·75). In autumn forage, the combination with straw did no…
An Uncommon Pathway in the Biosynthesis of Acetylenic Fatty Acids in Mosses
1995
Although more than 600 acetylenic compounds of various structures have been found in plants [1], hardly anything is known about the formation of the triple bonds. The acetylenes so far known from Bryophytes, have been identified as long chain fatty acids with a characteristic arrangement of one triple bond and one to three double bonds.
Einführung einer Dreifachbindung in das Bicyclo[6.1.0]nonan-Gerüst
1987
Ausgehend von den auf verschiedenen Wegen zuganglichen Ketonen 1a–c wird die Einfuhrung einer Dreifachbindung in das Bicyclo[6.1.0]nonan-Gerust mit Hilfe der Selenadiazol-Methode untersucht. Dabei Konnen die hochgespannten Bicyclo-[6.1.0]nonine 2a und 2b in reiner Form isoliert werden. Masgeblich fur die Position der Dreifachbindung ist die Regioselektivitat der Ringschlusreaktion bei der Selenadiazolbildung. Introduction of a Triple Bond into the Bicyclo[6.1.0]nonane Skeleton The introduction of a triple bond into the bicyclo[6.1.0]nonane skeleton is investigated by applying the selenadiazole method to the ketones 1a–c, accessible on different pathways. The highly strained bicyclo[6.1.0]no…