Hydrocarbons Titan

Diacetylene (HC=C—C=CH) has been identified as a component of the hydrocarbon rich atmospheres of Uranus Neptune and Pluto It is also present m the atmospheres of Titan and Triton satellites of Saturn and Neptune respectively... 

The reaction can be driven to the tetraalkoxide stage by addition of an amine or ammonia to scavenge the Hberated hydrochloric acid. The amine or ammonium hydrochloride that forms can be filtered from the reaction mass and the tetraalkyl titanate purified by distillation. If the reaction is mn in the starting alcohol as solvent, the chloride salts formed are in a finely divided state and difficult to filter. When the reaction is mn in the presence of an inert hydrocarbon solvent such as heptane or toluene, a much more readily filterable salt is obtained. The solution of cmde tetraalkyl titanate can be distilled to remove solvent and give a pure product (1,2). 

Fluoroall l-SubstitutedTitanates. Tetraliexafluoroisopropyl titanate [21416-30-8] can be prepared by the reaction of TiCl and hexafluoroisopropyl alcohol [920-66-17, in a process similar to that used for TYZOR TPT (7). Alternatively, it can be prepared by the reaction of sodium hexafluoroisopropoxide and TiCl ia excess hexafluoroisopropyl alcohol (8). The fluoroalkyl material is much more volatile than its hydrocarbon counterpart, TYZOR TPT, and is used to deposit titanium on surfaces by chemical vapor-phase deposition (CVD). 

The polymeric acyl titanate esters are viscous Hquids or waxes that are soluble ia hydrocarbon solvents and can be used as Ti02-dispersiag agents, water-repellent agents for textile fabrics, and mst inhibitors for steel. 

Titanium—Vanadium Mixed Metal Alkoxides. Titanium—vanadium mixed metal alkoxides, VO(OTi(OR)2)2, are prepared by reaction of titanates, eg, TYZOR TBT, with vanadium acetate ia a high boiling hydrocarbon solvent. The by-product butyl acetate is distilled off to yield a product useful as a catalyst for polymeri2iag olefins, dienes, styrenics, vinyl chloride, acrylate esters, and epoxides (159,160). 

Photolysis of Cp2TiAr2 in benzene solution yields titanocene and a variety of aryl products derived both intra- and intermolecularly (293—297). Dimethyl titan ocene photolyzed in hydrocarbons yields methane, but the hydrogen is derived from the other methyl group and from the cyclopentadienyl rings, as demonstrated by deuteration. Photolysis in the presence of diphenylacetylene yields the dimeric titanocycle (28) and a titanomethylation product [65090-11-1]. 

Without the influence of burning rate catalysts most of these hydrocarbon prop bits have similar burning rates and ballistic behavior. They may differ significantly in mechanical properties, particularly as a function of temp. Most hydrocarbon-based composites are used in larger rockets because of their ease of fabrication and high specific impulse. Polaris first and second stages, the Titan 3C booster rocket and Mlnuteman are all powered with composite proplnts... 

Successful attempts to reveal the secrets of the heterogeneous Titanian surface made use of radar astronomy. Donald B. Campbell and co-workers (in cooperation with other institutes) used the 300-m Arecibo radar telescope to send hundreds of kilowatts of microwave radiation towards Titan. The radar echoes recorded after about 2h indicated the presence of liquid hydrocarbons (Campbell et al., 2003 Lorenz, 2003). 

G. Mitri and co-workers calculated the minimum area of hydrocarbon lakes which would be necessary to preserve the relative methane humidity in the lower regions of the atmosphere. The result was surprising the calculations indicated that only between 0.002 and 0.2% of the total surface area of Titan would be required (Mitri et al., 2007). 

The reflection spectrum of the atmosphere is a measure of the albedo of the planet (Figure 10.4) and, despite the strong methane absorption in the red, Titan s disc looks orange principally due to scatter from the surface of dense methane-hydrocarbon clouds. Scatter from aerosol particles within the thick clouds obscures the surface of the moon although the radar analysis reveals considerable Chapman layer structure within the atmosphere and some interesting surface features. 

It is clear that a complex hydrocarbon polymer chemistry must exist in the atmosphere of Titan involving polyyne species, polynitrile species and mixtures of the two, and additional routes to polyaromatic hydrocarbon formation. This presents a significant problem for the gas chromatography/mass spectrometry instruments on the Huygens probe. There should be hydrocarbon fragments, producing perhaps... 

Liposphere The circulation of hydrocarbon-based materials in Titan s atmosphere, which is analogous to the hydrosphere (water cycles) on Earth... 

Navarro-GonzAlez R. el al. (2001). Production of Hydrocarbons and Nitriles by Electrical Processes in Titan s Atmosphere, Adv. Space Research 27(2) 271-282. 

As an example of thermolysis, consider the burnout of polyvinyl alcohol from a barium titanate compact in air. Initially, there is loss of hydroxyl and hydrogen side groups, leaving a conjugated hydrocarbon ... 

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. 

The cyclisation of alkenes by low valent titanium has also been applied to intramolecular processes. Thus the reduction of titanocenes bearing pendant alkenyl substituents [TiCl2(r -C5Me4XCH = CHR)2] (X = SiMe2, CH2, CHMe R = H, Me) provides chiral titanacyclopentanes shown in Scheme 2.16 The titan-acyclopentanes could then be cleaved with HC1 to provide new titanocene dichlorides in which the two cyclopentadienyl ligands were linked by a hydrocarbon chain. 

A variety of solvents have higher boiling points than that of water but do not have polar structures. The most accessible of these are the hydrocarbons, which come in a series from the smallest (methane) to higher homologs (ethane, propane, butane, and so on) and are abundant in the solar system. Methane, ethane, propane, butane, pentane, and hexane have boiling points of about 109, 184, 231, 273, 309, and 349 K, respectively, at standard terran pressure. Thus, at a mean surface temperature of 95 K, methane (which freezes at 90 K) would be liquid, implying that oceans of methane could cover the surface of Titan. 

Many discussions of life on Titan have considered the possibility that water, normally frozen at the ambient temperature, might remain liquid following heating by impacts.22 Life in this aqueous environment would be subject to the same constraints and opportunities as life in water. Water droplets in hydrocarbon solvents are, in addition, convenient cellular compartments for evolution, as Tawfik and Griffiths have shown in the laboratory.23 An emulsion of water droplets in oil is obtainable by simple shaking. This could easily be a model for how life on Titan achieves the isolation necessary for Darwinian evolution, and it provides an interesting alternative for membranes, discussed in earlier chapters as a common feature of terran life. 

Because of its reactivity, water destroys hydrolytically unstable organic species. Thus, a hypothetical form of life in a Titan hydrocarbon ocean would be less subject to the hydrolytic deamination of its nucleobases, and would be able to guide reactivity more easily than life in water. 

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