Titanation, acetylene

A titan acycl open tadi en e generated from an acetylene having an ester group at a suitable position reacts intramolecularly with this functional group, as exemplified by Eq. 9.13. Here, both carbon—titanium bonds of the titanacycle participate in the reaction to effect ring-closure [33]. 

Titanated vinylallenes generated from the coupling of acetylenes and propargyl carbonates [38] undergo facile, unidirectional electrocyclization to give cyclobutene derivatives under extremely mild reaction conditions as shown in Eq. 9.17 [39]. 

Oligomeric products, obtaining, 16 106 Oligomeric titanates, pyrolysis of, 25 121 Oligomerization, 23 329 acetylene, 1 181 butadiene, 4 373-374 in higher olefins, 17 712 ionic liquids in, 26 885-887 olefin, 16 111... 

Acetylene is the simplest unsaturated hydrocarbons and as such an understanding of its photochemistry is important. The reactions of ethynyl radicals (C H) are important in combustion as well as in the photochemistry of Jupiter and Titan atmospheres, although, unfortunately, C2H radical has apparently only very weak and complex absorption spectra in the visible and ultraviolet region and no LIF has been found. 

Clarke, D.W. Ferris, J.P. Titan haze Structure and properties of cyanoacetylene and cyanoacetylene-acetylene photopolymers. Icarus 1997, 127, 158-172. 

Acetylene has been observed in the atmospheres of Jupiter and Titan [33, 34] and more recently has been identified in significant abundance in comet Hyakutake [35]. Following the discovery of acetylene in Hyakutake, photochemical experiments have demonstrated [36] that this molecule is a likely precursor of C2, a widely observed component of comets. Acetylene itself may therefore be a ubiquitous constituent of comets. It has been proposed [37] that polymerization of acetylene in cometary impact on planetary atmospheres may be responsible for the formation of polycyclic aromatic hydrocarbons (PAHs) which may in turn be responsible for the colors of the atmospheres of Jupiter and Titan. Shock-induced polymerization of acetylene has been observed in the gas phase [38], and static high-pressure experiments have demonstrated polymerization of orthorhombic solid acetylene above 3 to... 

Whether formed from acetylene or from some other sources, PAHs are widely distributed in the solar system. As mentioned earlier, PAHs are found in the atmospheres of Jupiter and Titan [37]. They have also been detected in meteorites, including the Martian meteorite Allan Hills 84001 [43], in interplanetary dust [44], and in circumstellar graphite grains [45]. The ubiquity of these complex organic structures and their stability under extreme conditions is a significant factor in discussions of the origin of life on earth and the possibility of its existence elsewhere. 

Tetraoctyl titanate and Tetradecyl titanate. The Al/Ti molar ratio was two and aging time of the catalyst was 2 h at 120 C. The polymerizations were carried out at -78 °C for 14-23 h. The initial acetylene pressure was ca. 600 Torr. Polyacetylene films of 7-25 microns in thickness were obtained. All operations of the preparation procedure are described in detail elsewhere [6],... 

Ammonia Dibutyltin maleate Dibutyltin oxide Fluorosulfonic acid Phosphine Sodium ethylate Sodium hydride Tetrabutyl titanate Tetraisopropyl titanate p-Toluene sulfonic acid Zirconium butoxide catalyst, condensation reactions Dibutyltin diacetate Piperidine catalyst, conductive polymers Iron (III) toluenesulfonate catalyst, conversion of acetylene to acetaldehyde Mercury sulfate (ic) catalyst, copolymerization Di butyl ether catalyst, cracking Zeolite synthetic... 

There are many opportunities for modifying the catalytic system for acetylene polymerization, and the authors [38] found that one of the most effective methods is the introduction of long alkyl chains into alkyl aluminates and alkyl titanates as Ziegler catalysts, which suppressed the polymerization rate. PA was synthesized... 

The results may also have imphcations for chemical evolution in the solar system. Our results suggest that nitriles, amines, hydrazines of higher molecular weight and their derivatives, such as cyano-acetylenes and dinitriles, might have been synthesized. The presence of these important compounds, as precursors of biologically important compounds on Titan, implies that the chemical reactions postulated as the formation processes of bases and amino acids on the primitive Earth may be com-moi5)lace in the planetary system. 

Earth s silent siblings // eating acetylene on Titan I I three shields to guard the Earth // an arrow through the sky II summing it up with energy rate density II4 billion years of liquid balance H the Earth cracks, moves, and evolves // the limited palette of the first ocean... 

So life on Titan could move in the methane lakes and eat acetylene and other hydrocarbons as food. We can t see microbes from this distance, but we should be able to see their food in the atmosphere. In particular, scientists looked for the small hydrocarbons acetylene and ethene on Titan, as well as the hydrogen needed to burn them. But they couldn t find either—simulations have come up empty. The tastiest molecules for life are conspicuously absent. 

Organogermanium polymers were prepared by Kobayashi and coworicers via the reaction of a germylene (55) with acetylene monomers (56) in the presence of a rhodimn catalyst (Scheme 17). Polymer 57 contained a larger mole fraction of polyacetylene units titan germanium units in the backbone. 

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