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  • 1
    Electronic Resource
    Electronic Resource
    Free radical transport in a photochemical reactor (1978)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 24 (1978), S. 1134-1137 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690240632
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  • 2
    Electronic Resource
    Electronic Resource
    Spectroscopic studies of ligand exchange reactions in alkyl- and estertin PVC stabilizers (1986)
    Brookfield, Conn. : Wiley-Blackwell
    Journal of Vinyl and Additive Technology 8 (1986), S. 15-19 
    Details
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It has long been appreciated that mercaptoester/Cl exchange equilibria in mono- and dialkyltin mercaptoester/chlorides are important in understanding the stabilization of PVC by alkyltin mercaptoesters (1-3). More recently, IR studies have demonstrated the existence of similar equilibria in mixed mono-/dialkyltin systems; it has been suggested that these exchange reactions may be the source of synergism in the mixed mono-/dialkytin mercaptoester stabilizers (4). The ability to study these systems by IR and NMR methods is based upon the phenmenon of carbonyl to Sn coordination in these compounds and its sensitivity to molecular environment, principally the electronegativity of the tin atom. Our previous studies have now been extended to include estertin (β-carboalkoxyethyltin) mercaptoesters and mercaptoester/chlorides. In contrast to the simple alkyltin systems, the position of the respective mercaptoester/Cl exchange equilibria are dominated by carbonyl to Sn coordination from the ester group of the β-carboalkoxyethyl moiety. Based on the same phenomenon of carbonyl to tin coordination, the nature of alkyl- and estertin mercaptoesters containing alkyltin sulfides has been looked at to a very limited extent.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/vnl.730080106
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  • 3
    Electronic Resource
    Electronic Resource
    Differential calorimetric study of pine and poplar lignins between 300 and 525 KPresented in part at the 15th “Journées de Calorimétrie et d'Analyse Thermique” (JCAT) held at Brussels (Belgium), 14-16 May 1984. (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 32 (1986), S. 4561-4572 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070320421
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  • 4
    Electronic Resource
    Electronic Resource
    Infrared, Raman and inelastic neutron scattering study of phase transitions in trimethyloxosulphonium iodide, (CH3)3SOI (1985)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 16 (1985), S. 44-56 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Calorimetric (DTA), infrared, Raman and inelastic neutron scattering (INS) measurements have been performed for the trimethyloxosulphonium iodide compounds (CH3)3SOI and (CD3)SOI over the range 10-450 K. Two solid-solid phase transitions were found at about 200 and 250 K and the vibrational study showed that only the low-temperature crystalline form (III) is completely ordered. From a temperature dependence study of the optical and INS spectra it is concluded that methyl group reorintations are mainly involved in the phase (III)↔phase (II) transition, while the whole molecule reorientations about the three-fold axis, partly involved in the phase (II)↔phase (I) transformation, must be much slower than and decoupled from methyl motions. Finally, the potential barrier height against methyl rotations has been estimated to 13.3 kJ mol-1 from the observed torsional frequencies and compares favourably with the activation energies derived from previous NMR experiments (10.9 kJ mol-1) and from quasi-elastic neutron scattering results (10.6 kJ mol-1).
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250160109
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  • 5
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    The Laboratory Production of Complex Organic Molecules in Simulated Interstellar Ices (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Much of the volatiles in interstellar dense clouds exist in ices surrounding dust grains. Their low temperatures preclude most chemical reactions, but ionizing radiation can drive reactions that produce a suite of new species, many of which are complex organics. The Astrochemistry Lab at NASA Ames studies the UV radiation processing of interstellar ice analogs to better identify the resulting products and establish links between interstellar chemistry, the organics in meteorites, and the origin of life on Earth. Once identified, the spectral properties of the products can be quantified to assist with the search for these species in space. Of particular interest are findings that UV irradiation of interstellar ice analogs produces molecules of importance in current living organisms, including quinones, amphiphiles, and amino acids.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 198-200; NASA/CP-2002-211863
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  • 6
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    The Interstellar Production of Biologically Important Organics (2000)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: One of the primary tasks of the Astrochemistry Laboratory at Ames Research Center is to use laboratory simulations to study the chemical processes that occur in dense interstellar clouds. Since new stars are formed in these clouds, their materials may be responsible for the delivery of organics to new habitable planets and may play important roles in the origin of life. These clouds are extremely cold (less than 50 kelvin), and most of the volatiles in these clouds are condensed onto dust grains as thin ice mantles. These ices are exposed to cosmic rays and ultraviolet (UV) photons that break chemical bonds and result in the production of complex molecules when the ices are warmed (as they would be when incorporated into a star-forming region). Using cryovacuum systems and UV lamps, this study simulates the conditions of these clouds and studies the resulting chemistry. Some of the areas of progress made in 1999 are described below. It shows some of the types of molecules that may be formed in the interstellar medium. Laboratory simulations have already confirmed that many of these compounds are made under these conditions.
    Keywords: Astrophysics
    Type: Research and Technology 1999; 116-117; NASA/TM-2000-209618
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  • 7
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    Synthesis of Large Molecules in Cometary Ice Analogs: Physical Properties Related to Self-Assembly Processes (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The combination of realistic laboratory simulations and infrared observations have revolutionized our understanding of interstellar dust and ice-the main component of comets. Since comets and carbonaceous micrometeorites may have been important sources of volatiles and carbon compounds on the early Earth, their organic composition may be related to the origin of life. Ices on grains in molecular clouds contain a variety of simple molecules. The D/H ratios of the comets Hale-Bopp and Hyakutake are consistent with a primarily interstellar ice mixture. Within the cloud and especially in the presolar nebula through the early solar system, these icy grains would have been photoprocessed by the ultraviolet producing more complex species such as hexamethylenetetramine, polyoxymethylenes, and simple keones. We reported at the 1999 Bioastronomy meeting laboratory simulations studied to identify the types of molecules which could have been generated in pre-cometary ices. Experiments were conducted by forming a realistic interstellar mixed-molecular ice (H2O, CH3OH, NH3 and CO) at approximately 10 K under high vacuum irradiated with UV light from a hydrogen plasma lamp. The gas mixture was typically 100:50:1:1, however when different ratios were used material with similar characteristics was still produced. The residue that remained after warming to room temperature was analyzed by HPLC, and by several mass spectrometric methods. This material contains a rich mixture of complex compounds with mass spectral profiles resembling those found in IDPs and meteorites. Surface tension measurements show that an amphiphilic component is also present. These species do not appear in various controls or in unphotolyzed samples. Residues from the simulations were also dispersed in aqueous media for microscopy. The organic material forms 10-40 gm diameter droplets that fluoresce at 300-450 nm under UV excitation. These droplets have a morphology and internal structure which appear strikingly similar to those produced by extracts of the Murchison meteorite. Together, these results suggest a link between organic material photochemically synthesized on the cold grains in dense, interstellar molecular clouds and compounds that may have contributed to the organic inventory of the primitive Earth. For example, the amphiphilic properties of such compounds permit self-assembly into the membranous boundary structures that required for the first forms of cellular life.
    Keywords: Astrophysics
    Type: 1999 Meeting o BioAstronomy; Aug 01, 1999; Khilua, HI; United States
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  • 8
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    The Production of Amino Acids in Interstellar Ices: Implications for Meteoritic Organics (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Indigenous amino acids have been detected in a number of meteorites, over 70 in the Murchison meteorite alone. It has been generally accepted that the amino acids in meteorites formed in liquid water on an asteroid or comet parent-body. However, the water in the Murchison meteorite, for example, was depleted of deuterium, making the distribution of deuterium in organic acids in Murchison difficult to explain. Similarly, occasional but consistent meteoritic biases for non-terrestrial L amino acids cannot be reasonably rationalized by liquid water parent-body reactions. We will present the results of a laboratory demonstration showing that the amino acids glycine, alanine, and serine should result from the UV (ultraviolet) photolysis of interstellar ice grains. This suggests that some meteoritic amino acids may be the result of interstellar ice photochemistry, rather than having formed by reactions in liquid water. We will describe some of the potential implications of these findings for the organic materials found in primitive meteorites, in particular how interstellar ice synthesis might more easily accommodate the presence and distribution of deuterium, and the meteoritic bias for L amino acids.
    Keywords: Astrophysics
    Type: 65th Annual Meeting of the Meteoritical Society; Jul 21, 2002 - Jul 26, 2002; Los Angeles, CA; United States
    Format: text
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  • 9
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    Formation of Prebiotic Molecules in Interstellar and Cometary Ices (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We report here on our lab studies of ice photochemistry of large organic molecules under cometary conditions. We focus on polycyclic aromatic hydrocarbons (PAHs), their photoproducts, and their similarities to molecules seen in living systems today. We note that these kinds of compounds are seen in meteorites and we propose an explanation for both their formation and their observed deuterium enrichments.
    Keywords: Astrophysics
    Type: Bioastronomy Conference 1999: A New Era in the Search for Life in the Universe; Aug 02, 1999 - Aug 06, 1999; Kohala Coast, HI; United States
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  • 10
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    The Amino Acid Composition of the Sutter's Mill Carbonaceous Chondrite (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In contrast to the Murchison meteorite which had a complex distribution of amino acids with a total C2 to Cs amino acid abundance of approx.14,000 parts-per-billion (ppb) [2], the Sutters Mill meteorite was found to be highly depleted in amino acids. Much lower abundances (approx.30 to 180 ppb) of glycine, beta-alanine, L-alanine and L-serine were detected in SM2 above procedural blank levels indicating that this meteorite sample experienced only minimal terrestrial amino acid contamination after its fall to Earth. Carbon isotope measurements will be necessary to establish the origin of glycine and beta-alanine in SM2. Other non-protein amino acids that are rare on Earth, yet commonly found in other CM meteorites such as aaminoisobutyric acid (alpha-AIB) and isovaline, were not identified in SM2. However, traces of beta-AIB (approx.1 ppb) were detected in SM2 and could be" extraterrestrial in origin. The low abundances of amino acids in the Sutter's Mill meteorite is consistent with mineralogical evidence that at least some parts of the Sutter's Mill meteorite parent body experienced extensive aqueous and/or thermal alteration.
    Keywords: Astrophysics
    Type: GSFC.OVPR.6657.2012 , 75th Annual Meeting of the Meteoritical Society; Aug 12, 2012 - Aug 17, 2012; Cairns; Australia
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