Search results for "Butane"
showing 10 items of 184 documents
Cardopatine and isocardopatine, two novel cyclobutane substances from Cardopatium corymbosum
1978
Two new natural substances containing a cyclobutane unit, cardopatine and isocardopatine, the trans and cis isomers respectively of 5,5″ (cyclobut-1,2-ylene-diethynylene)bis 2,2′-bithiophene), together with the known α-terthienyl and 5-(but-3-en-1-ynyl)-2,2′-bithienyl, have been isolated from the roots of Cardopatium corymbosum. Evidence is given that the novel cyclobutane substances are not the products of a spontaneous dimerization of a bithienyl monomeric unit. Structure determination and conformational analysis are reported.
Selective Hydrogenation of 1,3-Butadiene to 1-Butene by Pd(0) Nanoparticles Embedded in Imidazolium Ionic Liquids
2005
The reduction of Pd(acac)2 (acac=acetylacetonate), dissolved in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI⋅PF6) or tetrafluoroborate (BMI⋅BF4) ionic liquids, by molecular hydrogen (4 atm) at 75 °C affords stable, nanoscale Pd(0) particles with sizes of 4.9±0.8 nm. Inasmuch as 1,3-butadiene is at least four times more soluble in the BMI⋅BF4 than butenes, the selective partial hydrogenation could be performed by Pd(0) nanoparticles embedded in the ionic liquid. Thus, the isolated nanoparticles promote the hydrogenation of 1,3-butadiene to butenes under solventless or multiphase conditions. Selectivities up to 97% in butenes were observed in the hydrogenation of 1,3-butadiene by Pd…
[39] DNA damage induced by ultraviolet and visible light and its wavelength dependence
2000
Publisher Summary DNA damage induced by solar radiation in mammalian cells consists largely of two types of modification: pyrimidine dimers and oxidative modifications. Pyrimidine dimmers that can be subdivided into cyclobutane pyrimidine dimmers, (CPDs) and (6-4) photoproducts are the characteristic and most abundant modifications after direct excitation of DNA, although they can also be formed indirectly by energy transfer from other excited molecules such as carbonyl compounds. Oxidative DNA damage, which includes various pyrimidine and purine modifications, sites of base loss (AP sites), and strand breaks, is generated in only low yield after direct excitation of DNA (except at very sho…
Durch elektronenübertragung initiierte diradikalische polykombination zu linearen und cyclischen polyanionen, 1. Umsetzung des protonierten dimeren v…
1975
Die Umsetzung von 1,4-Diphenyl-1,4-bis[4-(1-phenylvinyl)phenyl]butan (1)–des protonierten Dimeren des 1,4-Bis(1-phenylvinyl)benzols (2)–mit Natrium in THF wird beschrieben und diskutiert. Die Reaktionsprodukte werden durch GPC, NMR- und Massenspektren charakterisiert. The reactions of 1,4-diphenyl-1,4-bis[4-(1-phenylvinyl)phenyl]butane (1)—the protonized dimer of 1,4-bis(1-phenylvinyl)benzene (2)—with sodium in THF is described and discussed. The reaction products are characterized by GPC, NMR, and mass spectra.
Cyclobutane Pyrimidine Photodimerization of DNA/RNA Nucleobases in the Triplet State
2010
The photoinduced formation of cyclobutane pyrimidine dimers in the triplet excited state of the DNA/RNA pyrimidine nucleobases pairs has been studied at the CASPT2 level of theory. A stepwise mechanism through the triplet state of the homodimer is proposed for the pairs of nucleobases cytosine, thymine, and uracil involving a singlet−triplet crossing intermediary structure of biradical character representing the most favorable triplet state conformation of the nucleobases as found in the DNA environment. The efficiency of the mechanism will be modulated by two factors: the effectiveness of the triplet−triplet energy transfer process from a donor photosensitizer molecule, which relates to th…
The head-to-head photodimer of indeno-indene.
2020
Irradiation of 1-(1-benzocyclobutenylidene)benzocyclobutene gives indenoindene and its head-to-head photodimer nonacyclo[9.7.7.72,10.01,11.02,10.03,8.012,17.019,24.026,31]dotriaconta-3,5,7,12,14,16,19,21,23,26,28,30-dodecaene, C32H24. The molecule is built from four essentially planar indane units attached to an elongated cyclobutane ring. In the crystal, C—H...π interactions connect molecules into layers parallel to the bc plane.
Crystal structure of bis[μ-1,4-bis(diphenylphosphanyl)butane-κ2P:P′]bis[(3,4,7,8-tetramethyl-1,10-phenanthroline-κ2N,N′)copper(I)] bis(hexafluoridoph…
2016
The dication of the title compound, [Cu2(C28H28P2)2(C16H16N2)2](PF6)2·2CH2Cl2, has crystallographically imposed inversion symmetry. The copper(I) cation is coordinated in a distorted tetrahedral geometry by two N atoms of a chelating 3,4,7,8-tetramethyl-1,10-phenanthroline ligand and two P atoms of two bridging 1,4-bis(diphenylphosphanyl)butane ligands, forming a 14-membered ring. An intramolecular π–π interaction stabilizes the conformation of the dication. In the crystal, dications are linked by π–π interactions involving adjacent phenanthroline rings, forming chains running parallel to [111]. Weak C—H...F hydrogen interactions are also observed.
A new 3-D polymeric spin transition compound: [tris(1,4-bis(tetrazol-1-yl)butane-N1,N 1′)iron(II)] bis(perchlorate)
2001
A series of novel polymeric compounds of formula [M(btzb)3][ClO4]2 (Mll = Fe, Ni or Cu) with btzb = 1,4-bis-(tetrazol-1-yl)butane have been prepared and their physical properties investigated. The btzb ligand has been prepared and its crystal structure determined, together with a tentative crystal structure of the 3-D compound [Fe(btzb)3][ClO4]2. The model of the latter shows two symmetry-related, interpenetrating Fe-btzb networks in which the iron(II) ions approach each other as close as 8.3 and 9.1 A. This supramolecular catenane undergoes a sharp thermal spin transition around 160 K with hysteresis (20 K) along with a pronounced thermochromic effect. The spin crossover behaviour has been…
Visualization of inert gas wash-out during high-frequency oscillatory ventilation using fluorine-19 MRI
2010
High-frequency oscillatory ventilation is looked upon as a lung-protective ventilation strategy. For a further clarification of the physical processes promoting gas transport, a visualization of gas flow and the distribution of ventilation are of considerable interest. Therefore, fluorine-19 magnetic resonance imaging of the imaging gas octafluorocyclobutane (C(4) F(8) ) during high-frequency oscillatory ventilation was performed in five healthy pigs. For that, a mutually compatible ventilation-imaging system was set up and transverse images were acquired every 5 sec using FLASH sequences on a 1.5 T scanner. Despite a drop in signal-to-noise ratio after the onset of high-frequency oscillato…
Squaric Acid-Based Radiopharmaceuticals for Tumor Imaging and Therapy.
2021
Targeting vectors bound to a chelator represent a significant fraction of radiopharmaceuticals used nowadays for diagnostic and therapeutic purposes in nuclear medicine. The use of squaramides as coupling units for chelator and targeting vector helps to circumvent the disadvantages of several common coupling methods. This review gives an overview of the use of squaric acid diesters (SADE) as linking agents. It focuses on the conjugation of cyclic chelators, e.g., DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), as well as hybrid chelators like AAZTA5 (6-pentanoic acid-6-amino-1,4-diazepine tetracetic acid) or DATA5m (6-pentanoic acid-6-amino-1,4-diazapine-triacetate) to diff…