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1.
Titan is the only moon in the solar system with a substantial atmosphere. The organic chemistry of its N2–CH4 atmosphere may resemble that of the earth's primitive atmosphere before life arose. The investigation of the synthesis of prebiotic molecules in Titan's atmosphere and the atmospheric and surface environments of this planet-sized moon will be the focal point of the Cassini Project proposed to the European Space Agency for an international Saturn Orbiter/Titan Probe mission. 相似文献
2.
Nadia Balucani Piergiorgio Casavecchia 《Origins of life and evolution of the biosphere》2006,36(5-6):443-450
We have investigated gas-phase reactions of N(2D) with the most abundant hydrocarbons in the atmosphere of Titan by the crossed molecular beam technique. In all cases, molecular
products containing a novel CN bond are formed, thus suggesting possible routes of formation of gas-phase nitriles in the
atmosphere of Titan and primordial Earth. The same approach has been recently extended to the study of radical–radical reactions,
such as the reaction of atomic oxygen with the CH3 and C3H5 radicals. Products other than those already considered in the modeling of planetary atmospheres and interstellar medium have
been identified.
Presented at: National Workshop On Astrobiology: Search For Life In The Solar System, Capri, Italy, 26 to 28 October, 2005. 相似文献
3.
François Raulin Didier Mourey Gérard Toupance 《Origins of life and evolution of the biosphere》1982,12(3):267-279
Numerous experiments have already been performed, simulating the evolution of gaseous mixtures containing CH4 when submitted to energy flux. From their results, it appears that a variety of organic compounds, including unsaturated hydrocarbons and nitriles such as HCN, can be synthesized into noticeable amounts from CH4–N2 mixtures. In particular, systematic studies of the influence of the composition of the mixture on the nature and amount of synthesized compounds show that organic volatile nitriles, and particularly cyanoacetylene and cyanogen, are formed only in media rich in nitrogen. Those nitriles have been identified very recently in the atmosphere of Titan, and thus, data from such laboratory experiments may provide important indirect information on the organic chemistry occuring at the periphery of this satellite of Saturn. However, during these experiments, there is a continuous formation and accumulation of molecular hydrogen, which does not occur in the atmosphere of Titan, because of H2 escape. In order to reassess the data already available from this type of laboratory studies, experiments on CH4–N2 atmospheres, with and without H2 escape, have been recently performed. The influence of this parameter on the chemical evolution of the atmosphere and on the nature and relative quantities of organic compounds has been studied.After reviewing these experiments, implications of the obtained results on the organic chemistry at the periphery of Titan are discussed.Paper presented at the 6th College Park Colloquium, October 1981. 相似文献
4.
Kimihiko Goto Masataka Kinjo Keiji Hashimoto Masahiro Ishigami 《Journal of molecular evolution》1986,23(2):113-118
Summary Various hydrocarbons were synthesized by high-frequency discharge in a primordial terrestrial model atmosphere. The products were extracted by benzene or methanol and analyzed by GC-MS. The mean carbon chain length of the hydrocarbons formed by the discharge through pure CH4 gas was less than 6. Benzene was also obtained. Some isomers were obtained for each of the hydrocarbons containing a given number of carbons. When a small amount of C2H2 was added to the CH4, longer chain compounds were formed, as compared with discharge in CH4 only. However, when the amount of C2H2 was increased, unextractable high molecular weight compounds were produced. The amounts of products decreased as the mixing ratio of CO2 to CH4 increased. No hydrocarbons were detected when the ratio of CO2/CH4 exceeded 1. 相似文献
5.
F. Raulin P. Bruston P. Coll D. Coscia M-C. Gazeau L. Guez E. de Vanssay 《Journal of biological physics》1995,20(1-4):39-53
With a dense N2-CH4 atmosphere rich in organics, both in gas and aerosol phases, and with the possible presence of hydrocarbons oceans on its surface, Titan, the largest satellite of Saturn, appears as a natural laboratory to study chemical evolution toward complex organic systems, in a planetary environment and over a long time scale. Thanks to many analogies with planet Earth, it provides a unique way to look at the various physical and chemical processes, and their couplings which may have been involved in terrestrial prebiotic chemistry. Indeed, analogies with the Earth have a limit since Titan's temperatures are much lower than on the Earth and since liquid water is totally absent. However, from that aspect, Titan also serves as a reference laboratory worth studying — indirectly — the role of liquid water in exobiology. The Cassini-Huygens mission currently developed by NASA and ESA will send an orbiter around Saturn and Titan and a probe in Titan's atmosphere. This mission which will be launched in 1997 for an expected arrival in 2004, offers a unique opportunity to study in detail extra-terrestrial, not life-controled, organic processes, and consequently it will have significant implications in the fields of exobiology and the origins of life.This paper is dedicated to the memory of Cyril PONNAMPERUMA who largely contributed to the development of the scientific fields of Chemical Evolution and Exobiology. 相似文献
6.
《Inorganica chimica acta》1986,119(2):149-163
Kinetics of the base-induced decomposition of five 2-alkoxyethyl(aquo)cobaloximes, ROCH2CH2- Co(D2H2)OH2 (R = C6H5, CF3CH2, CH3, CH3CH2, (CH3)2CH), have been studied manometrically in aqueous base, ionic strength 1.0 M (KC1) at 25.0± 0.1 °C under an argon atmosphere. For the complexes with good leaving group alkoxide substituents (R = C6H5 and CF3CH2) the reactions are first- order in cobaloxime and first-order in hydroxide ion and produce stoichiometric amounts of ethylene and leaving group alcohol (ROH). NMR observation of decomposing solutions and workup of cobalt chelate products show that the reaction is initiated by hydroxide ion attack on an equatorial quaternary carbon leading to formation of an altered cobal- oxime product in which one of the Schiff's base linkages has become hydrated. For the remainer of the complexes the yield of ethylene is less than stoichiometric and pH-dependent, and the ethylene evolving reaction is second-order in hydroxide ion activity. The yield-limiting side reaction is shown to be base-catalyzed formation of a base-stable but photolabile alkoxyethylcobaloxime analog in which a Schiff's base linkage of the chelate has become hydrated, β-Elimination to form alkyl vinyl ethers was not observed for any of the alkoxyethylcobal- oximes. The second-order dependence of ethylene formation on hydroxide ion activity for R = CH3, CH2CH3, and CH(CH3)2 is discussed at some length, but is not well understood at present. 相似文献
7.
Rausch Felix Schicht Martin Bräuer Lars Paulsen Friedrich Brandt Wolfgang 《Journal of molecular modeling》2014,20(11):1-12
The prospects of a control for a novel gallium nitride pseudo-halide vapor phase epitaxy (PHVPE) with HCN were thoroughly analyzed for hydrocarbons–NH3–Ga gas phase on the basis of quantum chemical investigation with DFT (B3LYP, B3LYP with D3 empirical correction on dispersion interaction) and ab-initio (CASSCF, coupled clusters, and multireference configuration interaction including MRCI+Q) methods. The computational screening of reactions for different hydrocarbons (CH4, C2H6, C3H8, C2H4, and C2H2) as readily available carbon precursors for HCN formation, potential chemical transport agents, and for controlled carbon doping of deposited GaN was carried out with the B3LYP method in conjunction with basis sets up to aug-cc-pVTZ. The gas phase intermediates for the reactions in the Ga-hydrocarbon systems were predicted at different theory levels. The located π-complexes Ga…C2H2 and Ga…C2H4 were studied to determine a probable catalytic activity in reactions with NH3. A limited influence of the carbon-containing atmosphere was exhibited for the carbon doping of GaN crystal in the conventional GaN chemical vapor deposition (CVD) process with hydrocarbons injected in the gas phase. Our results provide a basis for experimental studies of GaN crystal growth with C2H4 and C2H2 as auxiliary carbon reagents for the Ga-NH3 and Ga-C-NH3 CVD systems and prerequisites for reactor design to enhance and control the PHVPE process through the HCN synthesis. 相似文献
8.
The reduction of NiX2(PCy3)2 (X = Cl, Br; PCy3 = tricyclohexylphosphine) in toluene with sodium sand under argon affords [NiX(PCy3)2]2 or Ni(PCy3)3. In the same way starting from NiX2P2 [X = Cl, Br; P = P(C2H5)3, P(CH2CH2CH2CH3)3, P(C2H5)2 C6H5] the tetracoordinate Ni(0) complexes NiP4 are obtained. These give NiP3(N2) under nitrogen. The electronic spectra of Ni(0) and Ni(I) complexes, both in the solid state and solution, are reported. 相似文献
9.
Coll Patrice Coscia David Gazeau Marie-Claire Guez Lionel Raulin François 《Origins of life and evolution of the biosphere》1998,28(2):195-213
Titan, the largest satellite of Saturn, has an atmosphere chiefly made up of N2 and CH4, and including many organics. This atmosphere also partly consists of hazes and aerosol particles which shroud the surface of this satellite, giving it a reddish appearance. The aerosols observed in Titan's atmosphere are thought to be synthesized at high altitudes (>300 km) and fall to the surface. Varying with temperature profiles, condensation phenomena take place in the lower atmosphere, about 100 km below. These solid particles, often called tholins, have been currently investigated for many years by laboratory scientists and physics modellers. This paper assesses past research and results in different fields (elemental composition, optical constants, pyrolysis, particle size), highlighting interests and questions aroused by these studies. It also presents the latest results and advances, and concludes with existing problems and future pathways. 相似文献
10.
UV light has been the most important energy source on the primitive Earth. However, very few experiments have been performed to test directly the possible role of this energy source on the chemical evolution of the primitive atmosphere, mainly on account of experimental difficulties. Experiments are generally performed with other excitations, mainly electric discharge, and it is frequently assumed that UV irradiation would give similar results.As theoretical considerations make this assumption questionable, direct experimental controls have been undertaken: Model primitive atmospheres have been submitted to 147 nm UV light and the gaseous phase has been analysed. Preliminary qualitative results concerning CH4–NH3 atmospheres are reported.Irradiation of pure CH4 gives rise to the synthesis of a large number of hydrocarbons, mainly saturated hydrocarbons but including also unsaturated ones as, C2H2, C2H4, C3H6, C3H4. These insaturated hydrocarbons are synthetized at a very low rate when ammonia is present in the medium.Irradiations of CH4–NH3 mixtures give rise, in addition to hydrocarbons, to important amounts of HCN (about 0.1%) and to lesser amounts of CH3CN and C2H5CN. No unsaturated nitriles such as acrylonitrile and cyanoacetylene have been detected. Search for amines is in progress.These results evidence that UV irradiation may contribute largely to synthesis of HCN in CH4–NH3 atmospheres and, consequently to the synthesis of many biochemical compounds that can be derivated from HCN. However, synthesis of other compounds, such as pyrimidines, which can derivate from other nitriles, such as cyanoacetylene, cannot be initiated only by UV light, contrary to electric discharges. In addition, if electric discharges are very efficient for synthesis of nitriles in CH4–N2 atmospheres, there is not yet evidence that UV light is able to do so.Presented at the 2nd ISSOL Meeting and the 5th ICOL in Kyoto, 5–10 April, 1977. 相似文献
11.
Biomass fast pyrolysis in a fluidized bed reactor under N2, CO2, CO, CH4 and H2 atmospheres 总被引:1,自引:0,他引:1
Biomass fast pyrolysis is one of the most promising technologies for biomass utilization. In order to increase its economic potential, pyrolysis gas is usually recycled to serve as carrier gas. In this study, biomass fast pyrolysis was carried out in a fluidized bed reactor using various main pyrolysis gas components, namely N2, CO2, CO, CH4 and H2, as carrier gases. The atmosphere effects on product yields and oil fraction compositions were investigated. Results show that CO atmosphere gave the lowest liquid yield (49.6%) compared to highest 58.7% obtained with CH4. CO and H2 atmospheres converted more oxygen into CO2 and H2O, respectively. GC/MS analysis of the liquid products shows that CO and CO2 atmospheres produced less methoxy-containing compounds and more monofunctional phenols. The higher heating value of the obtained bio-oil under N2 atmosphere is only 17.8 MJ/kg, while that under CO and H2 atmospheres increased to 23.7 and 24.4 MJ/kg, respectively. 相似文献
12.
This paper presents the experimental results of biomass pyrolysis in a laboratory argon/hydrogen plasma reactor. The samples tested were wood and rice husk. The gaseous product was found to contain mainly H2, CO, C2H2 and CH4. The conversion of carbon and oxygen from the biomass feed to gaseous product can reach up to 79 % and 72 %, respectively. The results indicate that plasma pyrolysis of biomass may be a useful way for gaseous fuel production. 相似文献
13.
Denitrification, Acetylene Reduction, and Methane Metabolism in Lake Sediment Exposed to Acetylene 总被引:8,自引:6,他引:2
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Roger Knowles 《Applied microbiology》1979,38(3):486-493
Samples of sediment from Lake St. George, Ontario, Canada, were incubated in the laboratory under an initially aerobic gas phase and under anaerobic conditions. In the absence of added nitrate (NO3−) there was O2-dependent production of nitrous oxide (N2O), which was inhibited by acetylene (C2H2) and by nitrapyrin, suggesting that coupled nitrification-denitrification was responsible. Denitrification of added NO3− was almost as rapid under an aerobic gas phase as under anaerobic conditions. The N2O that accumulated persisted in the presence of 0.4 atm of C2H2, but was gradually reduced by some sediment samples at lower C2H2 concentrations. Low rates of C2H2 reduction were observed in the dark, were maximal at 0.2 atm of C2H2, and were decreased in the presence of O2, NO3−, or both. High rates of light-dependent C2H2 reduction occurred under anaerobic conditions. Predictably, methane (CH4) production, which occurred only under anaerobiosis, was delayed by added NO3− and inhibited by C2H2. Consumption of added CH4 occurred only under aerobic conditions and was inhibited by C2H2. 相似文献
14.
Using molecular simulations, we studied a diverse collection of zeolite–imidazolate frameworks (ZIFs) to evaluate their performances in adsorption- and membrane-based gas separations. Molecular simulations were performed for both single-component gases (CH4, CO2, H2 and N2) and binary gas mixtures (CO2/CH4, CO2/N2, CO2/H2 and CH4/H2) to predict the intrinsic and mixture selectivities of ZIFs. These two selectivities were compared to discuss the importance of multi-component mixture effects on making predictions about the separation performance of a material. Gas separation performances of ZIFs were compared with other nanoporous materials and our results showed that several ZIFs can outperform well-known zeolites and metal–organic frameworks in CO2 separations. Several other properties of ZIFs such as gas permeability, working capacity and sorbent selection parameter were computed to identify the most promising materials in adsorption- and membrane-based separation of CO2/CH4, CO2/N2, CO2/H2 and CH4/H2. 相似文献
15.
N-substituted ethylcarbamates form with thorium nitrate the complexes Th(NO3)4·3RHNC(O)OC2H5 (where R = CH3, C2H5, C6H5(CH3)CH) and with lanthanum nitrate the complexes La(NO3)3· 2RR′NC(O)OC2H5·3H2O (where R = CH3, C2H5, C6H5(CH3)CH; R′ = H and R = CH3, C6H5; R′ = C2H5 or R = R′ = CH3). In addition the anhydrous La(NO3)3·3(C2H5)2NC(O)OC2H5 has been isolated. From the IR spectra it is deduced that the carbamates coordinate the metal through the carbonyl oxygen atom and that the nitrato groups act as chelated ligands. 1H nmr spectral data of the complexes are reported and discussed. 相似文献
16.
《Inorganica chimica acta》1987,134(1):139-142
A new series of heterocyclic telluronium salts (C4H8OTeRX: R=CH3CH2, CH2CHCH2, CH3, C4H9, X=I; R=CH2CHCH2, X=Br; R=CH3, X=ClO4; R=CH3, CH3CH2, C6H5, X=BPh4) have been prepared. Conductivity measurements in dimethylsulphoxide (DMSO) and N,N-dimethytl- formamide (DMF) have shown that there is an ion pair interaction between the anion and the tellurium cation.1H NMR studies showed that there is no reaction between the solute and the solvent. All compounds are stable in solution in DMSO. Infra-red spectra are reported and discussed. 相似文献
17.
Hiroshi Mizutani Hitoshi Mikuni Makoto Takahasi Haruhiko Noda 《Origins of life and evolution of the biosphere》1975,6(4):513-525
The photochemical reaction of HCN at 184.9 nm is studied in the gas phase. (CN)2, H2, CH4, NH3, N2H4, C2H6, and CH3NH2 are identified as gas phase products, and a reaction mechanism is proposed. HCN polymers** are also obtained as solid reaction products, and their structure is investigated by Infrared Spectroscopy, UV-Visible Spectroscopy, Mass Spectrometry, and Amino acid Analysis. The process and nature of the formation of the polymers are discussed. 相似文献
18.
The sporangiophore of the fungus Phycomyces blakesleeanus has the property of growing away from a barrier which is few mm from the growing zone of the sporangiophore (avoidance or autochemotropic response). A model has been published (Cohen, R.J., Jan, N.Y., Matricon, J., Delbrück, M.: J. Gen. Physiol. 66, 67–95 (1975)). To explain the avoidance response which postulates that the sporangiophore emits and readsorbs a volatile growth-promoting effector (gas X) and that the barrier modifies the effector distribution by acting as an aerodynamic obstacle, causing a higher concentration of gas X on the side of the sporangiophore closer to the barrier. From this model we deduced three properties of the gas X. Of the several gases tested (N2, CO2, CH4, C2H2, C2H4, C2H6) only ethylene (C2H4) had all these three properties, a finding which suggests that it has a role in the avoidance response (autochemotropism).Abbreviation Spph
Sporangiophore 相似文献
19.
In-situ partial pressures of hydrogen in anoxic profundal lake sediments reached values of up to 5 Pa which were more than 5 orders of magnitude lower than the partial pressures of methane. Analysis of gas bubbles collected from anoxic submerged paddy soil showed H2 partial pressures in the range of 1.8 ± 1.3 Pa being ca. 4 orders of magnitude lower than the CH4 partial pressures. H2 emission rates, on the other hand, were less than 3 orders of magnitude lower than the CH4 emission rates indicating that H2 and CH4 were oxidized to a different extent in the rhizosphere of the soil before they reached the atmosphere, or that H2 was produced by the plants. More than 70% of the emitted H2 reached the atmosphere via plant-mediated flux. The rest was emitted via ebullition from the anoxic soil and, in addition, was produced in the paddy water. A significant amount of H2 was indeed found to be produced in the water under conditions where thallic algae and submerged parts of the rice plants produced oxygen by photosynthesis. Very little H2 was emitted via molecular diffusion through the paddy water; in addition, this amount was less than expected from the degree of supersaturation and the diffusional emission rate of CH4 indicating a relatively high rate of H2 consumption in the surface film of the paddy water. The total H2 source strength of rice paddies and other freshwater environments was estimated to be less than 1 Tg yr-1, being negligible in the atmospheric budget of H2. 相似文献
20.
Regulation of growth in stem sections of deep-water rice 总被引:11,自引:0,他引:11
Submergence in water greatly stimulates internodal elongation in excised stem sections of deep-water rice (Oryza sativa L. cv. Habiganj Aman II) and inhibits growth of leaf blades and leaf sheaths. The highest rates of internodal growth have been observed in continuous light. Very little growth occurs in submerged sections kept in darkness or incubated under N2 in the light. The effect of submergence on the growth of deep-water rice is, at least in part, mediated by C2H4, which accumulates in the air spaces of submerged sections. This accumulation results from increased C2H4 synthesis in the internodes of submerged sections and reduced diffusion of C2H4 from the tissue into the water. Increased C2H4 levels accelerate internodal elongation and inhibit the growth of leaves. Compounds capable of changing the rate of C2H4 synthesis, namely aminoethoxyvinylglycine, an inhibitor of C2H4 synthesis, and 1-aminocyclopropane-1-carboxylic acid, the immediate, precursor of C2H4, have opposite effects on growth of internodes and leaves. The enhancement of internodal elongation by C2H4 is particularly pronounced in an atmosphere of high CO2 and low O2. The increase in C2H4 synthesis in internodes of submerged sections is primarily triggered by reduced atmospheric concentrations of O2. The rate of C2H4 evolution by internodes isolated from stem sections and incubated in an atmosphere of low O2 is up to four times greater than that of isolated internodes incubated in air. In contrast, C2H4 evolution from the leaves is reduced under hypoxic conditions. The effect of submergence on growth of stem sections of deep-water rice can be mimicked by exposing non-submerged sections to a gas mixture which is similar to the gaseous atmosphere in the internodal lacunae of submerged sections, namely 3% O2, 6% CO2, 91% N2 (by vol.) and 1 l l-1 C2H4. Our results indicate that growth responses obtained with isolated rice stem sections are similar to those of intact deep-water rice plants.Abbreviations ACC
1-aminocyclopropane-1-carboxylic acid
- AVG
aminoethoxyvinylglycine 相似文献