Interstellar alcohol

As an example, we shall discuss the interstellar synthesis of a compound which is produced on Earth in millions of tons per year methanol. This simplest alcohol was obtained by Robert Boyle in 1661 from the dry distillation of wood. In the molecular clouds of the universe, it is likely that hydrogenation of CO on the surface of dust particles occurs according to the following scheme (Tielens and Charnley, 1997) ... 

H2C0, HCN, HC0+, HCC, C3N, C4H. The high density and temperature of black interstellar clouds facilitates a richer chemistry in which molecules such as dimethyl ether and ethyl alcohol are formed [1]. Figure 1 summarizes the carbon compounds which have been found in interstellar space and their abundances relative to hydrogen. Note that the carbon compounds decrease in abundance with increasing complexity. 

The reported halflife of ethenol (vinyl alcohol) in the gas phase at room temperature is ca. 30 min [221], far shorter than our calculated 1028-1029 s. However, the 30 min halflife is very likely that for a protonation/deprotonation isomerization catalyzed by the walls of the vessel, rather than for the concerted hydrogen migration (Fig. 5.30) considered here. Indeed, the related ethynol has been detected in planetary atmospheres and interstellar space [222], showing that that molecule, in isolation, is long-lived. Even under the more confined conditions of the lab, ethenol can be studied in the gas phase [221, 223] and in solution [224]. All three methods predict very long halflives for the uncatalyzed reaction. 

Significantly, the photoproducts of interstellar ice simulations also include amphiphilic compounds having self-assembly properties [31]. Figure 8 shows micrographs of Murchison vesicles, as well as vesicles formed by products of interstellar ice simulations and known fatty acid-fatty alcohol mixtures. It is clear that the vesicle-forming behavior of all of these amphiphiles is... 

Let us compare abundance patterns in detail (Fig. 13), using the most complete sets of data available alcohols for the FTT reaction (Anders et al., 1974) and cyanoacetylenes in TMC-1 for interstellar molecules (Morris et al., 1976 Kroto et al., 1978 Broten et al., 1978 Langer et al, 1980). 

Fig. 13. The Fischer-Tropsch reaction produces homologous series in logarithmic distribution, as illustrated here by alcohols (Anders et al, 1974). From C2 upward, successive homo-logues form in fixed, molecular ratio C +t/C = a, where a is the probability of chain growth, typically 0.6-0.9. Interstellar cyanoacetylenes in the Taurus Molecular Cloud 1 likewise show a logarithmic distribution, of very similar slope (0.52 vs 0.59 for the FTT alcohols). Presumably they, too, formed by surface catalysis, rather than by gas-phase reactions...

Naphthalene, anthracene, and similar hydrocarbons are termed polycyclic aromatic hydrocarbons (PAHs) because they are composed of multiple aromatic rings. PAHs have been found in meteorites and identified in the material surrounding dying stars. Scientists have mixed PAHs with water ice in a vacuum at -260°C to simulate the conditions found in interstellar clouds. To simulate radiation emitted by nearby stars, they shined ultraviolet light on the mixture. About ten percent of the PAHs were converted to alcohols, ketones, and esters— molecules that can be used to form compounds that are important in biological systems. 

Properties Colorless gas (or liquid) sharp, intensely irritating odor lighter than air easily liquefied by pressure. Bp -33.5C, fp -77C, vap press of liquid 8.5 atm (20C), sp vol 22.7 cu ft/lb (70C), d (liquid) 0.77 at 0C and 0.6819 at bp. Very soluble in water, alcohol, and ether. Autoign temp 1204F (650C). Combustible. Note Ammonia is the first complex molecule to be identified in interstellar space. It has been observed in galactic dust clouds in the Milky Way and is believed to constitute the rings of the planet Saturn. 

An alternative source of prebiotic molecules on the early Earth is from meteorites. Carbonaceous chondrite meteorites contain abundant carbon, present in a variety of molecular forms, including amino acids, polyols such as sugars and sugar-alcohols. These molecules are all important to life and form key components of nucleic acids and cell membranes (Cooper et al., 2001). Similar molecular evidence for amino acids is found in even more ancient fragments of the early Universe -IDPs. These molecules formed either in the solar nebula or in an interstellar environment (Flynn et al., 2003). Comets have also been considered a viable potential source of prebiotic molecules although currently the view is that most organic material was delivered by asteroids rather than by comets (Dauphas Marty, 2002). 

CHgCNir. Many of the reactions involve radiative association. Dissociative electron-ion recombination then yields neutrals such as CH (methane), C2HgOH (ethanol) and CH CN (acetonitrile) [158). It is often joked that diffuse interstellar clouds contain enough grain alcohol to keep space travellers happy on their long journeys. In diffuse clouds, the reaction scheme is more varied and leads to smaller molecules in general. 

X 10 kg. Analyses of interstellar dust clouds and heavenly bodies fotmd on Earth, such as the Murchison meteorite, showed the presence of a variety of important prebiotic compotmds. such as amino acids, ureas, alcohols. aldehydes, purines, polycyclic aromatic hydrocarbons (PAH), and organic acids,"" highlighting the significance of extraterrestrial carbon delivery to Earth. 

PAHs comprise a large percentage of the carbon found in interstellar space. They have even been observed in interstellar ice (Halley s comet, for example). It has been shown that ultraviolet irradiation of PAHs in ice produces aromatic ketones (Chapter 9), alcohols (Chapter 7), and other compounds, suggesting a role of PAHs in prebiotic chemistry (see A Word about Methane, Marsh Gas, and Miller s Experiment, page 60). 

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