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At least 73 records · Page 4

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NASA NTRS1985

Dicarboxylic acid anhydride condensation with compounds containing active methylene groups. 4: Some 4-nitrophthalic anhydride condensation reactions

By 4-nitrophthalic anhydride condensation with acetoacetate in acetic anhydride and triethylamine solution with subsequent breakdown of the intermediate condensation product, 5-nitroindanedione-1,3 was obtained. A 4-nitrophthalic anhydride with acetic anhydride, according to reaction conditions, may yield two products: in the presence of potassium acetate and at high temperatures 4-(or 5-)-nitro-2-acetylbenzoic acid is formed: in the presence of triethylamine and at room temperature 5-( or 6-)-nitrophthalic acetic acid is isolated. A 4-nitrophthalic anhydride and malonic acid in pyridine solution according to temperature yield either 5-( or 6-)-nitrophthalic acetic acid or 4-(or 5-)-nitro-2-acetylbenzoic acid.

Oskaja, V.↗

NASA NTRS1986

Method for producing tetraphenoxide-n-aniloxy cyclo phosphazotriene

A method for producing tetraphenoxide-n-aniloxy cyclophosphazotriene, distinguished by the fact that tetraphenoxide dichlorocyclophosphazotriene is processed with an alkaline metal n-acetamidophenolate in an organic solvent, for example pyridine, during heating, after which the resulting compound is saponified in the present of a mineral or organic acid, for example, hydrochloric, and the desired product separated by well known techniques.

Khofbauer, Y. I.↗

NASA NTRS1986

The organic aerosols of Titan

A dark reddish organic solid, called tholin, is synthesized from simulated Titanian atmospheres by irradiation with high energy electrons in a plasma discharge. The visible reflection spectrum of this tholin is found to be similar to that of high altitude aerosols responsible for the albedo and reddish color of Titan. The real (n) and imaginary (k) parts of the complex refractive index of thin films of Titan prepared by continuous dc discharge through a 0.9 N2/0.1 CH4 gas mixture at 0.2 mb is determined from X-ray to microwave frequencies. Values of n (approx. 1.65) and k (approx. 0.004 to 0.08) in the visible are consistent with deductions made by groundbased and spaceborne observations of Titan. Many infrared absorption features are present in k(lambda), including the 4.6 micrometer nitrile band. Molecular analysis of the volatile components of this tholin was performed by sequential and nonsequential pyrolytic gas chromatography/mass spectrometry. More than one hundred organic compounds are released; tentative identifications include saturated and unsaturated aliphatic hydrocarbons, substituted polycylic aromatics, nitriles, amines, pyrroles, pyrazines, pyridines, pyrimidines, and the purine, adenine. In addition,acid hydrolysis produces a racemic mixture of biological and nonbiological amino acids. Many of these molecules are implicated in the origin of life on Earth, suggesting Titan as a contemporary laboratory environment for prebiological organic chemistry on a planetary scale.

Khare, B. N.↗

NASA NTRS1986

Vinyl stilbazoles

Vinyl pyridines including vinyl stilbazole materials and vinyl styrylpyridine oligomer materials are disclosed. These vinylpyridines form copolymers with bismaleimides which copolymers have good fire retardancy and decreased brittleness. The cure temperatures of the copolymers are substantially below the cure temperatures of the bismaleimides alone. Reinforced composites made from the cured copolymers are disclosed as well.

Parker, John A.↗

NASA NTRS1987

Structural panels

Parker, John A.↗

NASA NTRS1987

Degradation mechanisms of sulfur and nitrogen containing compounds during thermal stability testing of model fuels

The degradation behavior of n-dodecane (singly or in combination with S- and N-containing dopants) was studied using a modified Jet Fuel Thermal Oxidation Tester facility between 200 and 400 C. The products were analyzed by gas chromatography and mass spectrometry. The soluble products consisted mainly of n-alkanes and 1-alkenes, aldehydes, tetrahydrofuran derivatives, dodecanol and dodecanone isomers, C21-C24 alkane isomers, and dodecylhydroperoxide (ROOH) decomposition products. The major products were always the same, with and without dopants, but their distributions varied considerably. The 3,4-dimercaptotoluene and dibutylsulfide dopants added individually to n-dodecane interferred with the hydrocarbon oxidation at the alkylperoxy radical and the alkylhydroperoxide link, respectively, while the 2,5-dimethylpyrrole dopant inhibited ROOH formation. Pyridine, pyrrole, and dibenzothiophene added individually showed few significant effects.

Reddy, K. T.↗

NASA NTRS1988

Developing Crystallinity In Linear Aromatic Polyimides

New technique improves melt flow of polyimide. Uses chemical imidization or cyclodehydration techniques that do not cause significant decrease in molecular weight. Process involves dissolution of polyamide acid in amide solvent or mixture of ether and amide solvent at low percentage of solids followed by treatment of this solution with aprotic organic base, such as triethylamine or pyridine, for period of time prior to treatment with organic dehydrating agent. Latter treatments facilitates formation of polyimide. Useful for production of polyimide molding materials. Expected to have widespread application in preparation of easily processed adhesives, molding powders, and matrix resins.

St. Clair, Terry L.↗

NASA NTRS1989

NOx formation from the combustion of monodisperse n-heptane sprays doped with fuel-nitrogen additives

A series of experiments with simulated synthetic fuels were conducted in order to investigate the effect of droplet size on the conversion of fuel-nitrogen to NOx. Pyridine and pyrrole were added to n-heptane as nitrogen-containing additives and burned as monodisperse fuel droplets under various operating conditions in a spray combustion facility. The experimental results indicate that under stoichiometric and fuel-rich conditions, reducing the droplet size increases the efficiency of fuel-N conversion to NOx. This observation is associated with improved oxidation of the pyrolysis fragments of the additive by better oxygen penetration through the droplet flame zone. The dominant reactions by which fuel-N is transformed to NOx were also considered analytically by a premixed laminar flame code. The calculations are compared to the small droplet size results.

Sarv, Hamid↗

NASA NTRS1989

Iptycene synthesis: A new method for attaching a 2,3-anthracene moiety to the 9,10-positions of another anthracene moiety - Exceptional conditions for a Lewis acid catalyzed Diels-Alder reaction

An efficient three-step method for appending a 2,3-anthracene moiety to the 9,10-positions of an existing anthracene moiety is described. The first step uses excess 1,4-anthraquinone (3 equiv) and aluminum chloride (6 equiv) to obtain the anthracene-quinone cycloadduct (omission of the AlCl3 resulted in no adduct). The resulting diketone was reduced to the corresponding diol (excess LiAlH4), which was dehydrated to the arene with phosphorus oxychloride and pyridine. Specific examples include the preparation of heptipycene 8 from pentiptycene 6 (66 percent overall yield) and a similar conversion of 8 to the noniptycene 13 (75 percent overall yield). The methodology led to a markedly improved synthesis of tritriptycene 9 and the first synthesis of undecaiptycene 14.

Chen, Yong-Shing↗

NASA NTRS1994

A commercialized, continuous flow fiber optic sensor for trichloroethylene and haloforms

Purus, Inc. has commercialized a fiber optic chemical sensor using technology developed by Lawrence Livermore National Laboratory and licensed from The University of California. The basis for the sensor is the development of color within a reagent when exposed to an analyte. The sensor consists of an optrode, reagent delivery and recover system, fiber optic transmitter-receiver, controller, and display. Reagent is pumped through the optrode. Analyte diffuses across a gas permeable membrane and reacts with the reagent to form a colored product. The colored product is detected by measuring the absorbance of light from a 568 nm diode. Reagents are currently available for TCE and trihalomethanes. Initial reagent chemistry is based on the Fujiwara alkaline pyridine reaction. The optrode contacts only gas streams, but the volatility of the current analytes also allows measurements of aqueous streams, without being affected by aqueous interferents that are non-volatile. Sensitivity of the sensor has been demonstrated to 5 ppb aqueous solutions and 0.1 ppmv in flowing gas streams.

Wells, James C.↗

NASA NTRS1994

Oligomerization of mononucleotides on montmorillonite: A potential approach to the prebiotic synthesis of RNA

The condensation of the 5'-phosphorimidazolide of adenosine (ImpA) on montmorillonite in a pH 8 aqueous solution yields oligomers containing up to 10 monomer units. The regiospecificity of 3',5'-phosphodiester bond formation is enhanced by addition of 10% diadenosine pyrophosphate (AppA) to the reaction mixture. A series of activated derivatives of 5'-AMP was prepared to investigate the effect of the leaving group on oligomer formation. The benzimidazole and p-dimethylamino-pyridine derivatives gave the best yields of oligomers. Factors important for oligomer formation is discussed.

Ferris, James P.↗

NASA NTRS1994

Trans-Bis(acetato-o)bis(4-methylpyridine-N)copper(II)

The structure of trans-bis(acetato-O)bis(4-methyl- pyridine-N)copper(II), (Cu(C2H302)(sub 2)(C6H7N)(sub 2)), re- ported herein, represents a monomeric parent acetate complex with a distorted square-planar arrangement of acetate and 4-methylpyridine ligands around the Cu atom with the following distances and angles: Cu-N = 2.027 (4) and Cu-O1 = 1.950 (3) A; O1-Cu-N = 89.1 (2) and O1 -Cu-N' = 90.9 (2)deg. The Cu atom resides on a center of inversion. The most important dihedral angles are the angle between the 4-methylpyridine plane and the acetate plane (O1, O2, C21 and C22), 78.2 deg and the angle between the 4-methylpyridine ring and the coordination plane (Cu, N, O1), 31.6 deg.

Jedrzejas, Marek J.↗

NASA NTRS1995

Synthesis of Substituted 2,3,5,6-tetraarylbenzo(1,2-b:5,4-b')difurans

A series of substituted 2,3,5,6-tetraarylbenzo(l,2-b:5,4-b')difurans 1 was synthesized. This synthesis is based upon the photocyclization of 2,5-dibenzoylresorcinol dibenzyl ethers to the corresponding tetrahydrobenzo(1,2-b:5,4-b')difurans. Treatment of the photoproducts with methanesulfonyl chloride in pyridine afforded 1 in overall yields ranging from 30-72%. A number of these compounds have high fluorescence quantum yields (of phi(sub f) = 0.76-0.90), and their fluorescence spectra exhibit large solvatochromic shifts. These compounds may be suitable for use as fluorescent probes.

Abdul-Aziz, Mahmoud↗

NASA NTRS2001

The Organic Content of the Tagish Lake Meteorite

The Tagish Lake meteorite felt last year on a frozen take in Canada and may provide the most pristine material of its kind. Analyses have now shown this carbonaceous chondrite to contain a suite of soluble organic compounds (approximately 100 parts per million) that includes mono- and dicarboxylic acids, dicarboximides, pyridine carboxylic acids, a sulfonic acid, and both aliphatic and aromatic hydrocarbons. The insoluble carbon exhibits exclusive aromatic character, deuterium enrichment, and fullerenes containing 'planetary' helium and argon. The findings provide insight into an outcome of early solar chemical evolution that differs from any seen so far in meteorites.

Pizzarello, Sandra↗

NASA NTRS1996

Chemical Storage of Data

We investigate the possibility of storing data using H and F on a polymer to signify 0 and 1 bits. We show that the difference between the B-F and B-H interaction energies for either C5H5B or C3H3N2B is only slightly larger than the variation in B-F interaction energy with type of neighboring atoms. Pyridine (C5H5N) and (CH3)3P=O have a much larger difference in the H and F interaction energies. (CH3)3P=O may be better suited as a surface probe, because the interaction with neighboring data sites should be smaller.

Bauschlicher, Charles W., Jr.↗

NASA NTRS1997

Differentiating Between H and F or H and CN on C(III) or Si(III) Surfaces

A Sc tipped probe molecule yields a larger difference for the probe-H vs probe-F interaction energies than our previously studied, electron-rich pyridine (C5H5N) and (CH3)3PO probes. However, the electron-deficient Sc tipped probe does not eliminate the probe-nearest data neighbor interaction problem associated with the C(III) surface. The difference in the probe-H and probe-F interaction energies is smaller for Si(III) than C(III), making it more difficult to differentiate between these two atoms on Si(III). The larger lattice constant for Si(III) significantly reduces the data atom-data atom interaction energy as well as the probe-neighbor interaction energies. This means that the H/CN system which is not practical for C(III) due to the CN-CN repulsion, is possible for Si(III). The difference in the probe-H and probe-CN interaction energies is very large for the H/CN data storage system, making this the best system studied to date. This system could be used on C(III) if a hydrogen 'fence' is built around each data site, which corresponds to using only one quarter of the surface sites for data storage.

Bauschlicher, Charles W.↗

NASA NTRS1999

Tholins: Can They Provide a Substrate, Carbon and Nitrogen for Plant Production?

Tholin is a word coined to describe the entire class of complex organic solids produced in laboratory experiments where pre-biotic gaseous chemicals are subject to bombardment by high energy. The atomic composition of Titan tholin produced from 10 percent CH4 and 90 percent N2 in a simulation of Titan atmosphere irradiated by charged particles trapped in the magnetosphere of Saturn gave 67 percent C and 33 percent N. Hydrolysis of Titan tholin with 6N HCl produced a racemic mixture of biological and non-biological amino acids that was confirmed by GC/MS. Other tholins, that revealed the presence of amino acids, were UV tholin produced under possible primitive Earth conditions by irradiation of a mixture of gases (CH4, C2H6, NH3, H2S and liquid H2O) with long-wavelength ultraviolet light, representing the most abundant useful energy source for prebiological organic synthesis; Spark tholin in a crude simulation of Jupiter atmosphere using electrical discharge through a mixture of CH4, NH3, and H2O vapor. Pyrolytic GC/MS of Titan tholin produced more than one hundred organic compounds including saturated and unsaturated aliphatic hydrocarbons, substituted polycyclic aromatics, nitriles, amines, pyrroles, pyrazines, pyridines, pyrimidines, and the purine, adenine. Similar rich pyrolytic products were obtained with UV as well as Spark tholins. A range of two to four ring PAHs (Polycyclic Aromatic Hydrocarbons) in Spark as well as Titan tholins, some with one to four alkylation sites, were identified by two-step laser desorption/multiphoton ionization mass spectrometry and also confirmed by the synchronous fluorescence technique. Previous studies have demonstrated the potential for use of tholins as a source of carbon and energy by microbes. This paper describes studies that evaluate the potential for using different types of tholins as (a) a substrate for growing plants and (b) a source of carbon and nitrogen for plants. The data are interpreted in terms of the potential for using such tholins to grow plants for food in extraterrestrial habitats and also to speculate on the possibilities of abiotic evolution of plants.

Wignarajah, Kanapathipillai↗

NASA NTRS2003

Dissociative Ionization of Aromatic and Heterocyclic Molecules

Space radiation poses a major health hazard to humans in space flight. The high-energy charged particles in space radiation ranging from protons to high atomic number, high-energy (HZE) particles, and the secondary species they produce, attack DNA, cells, and tissues. Of the potential hazards, long-term health effects such as carcinogenesis are likely linked to the DNA lesions caused by secondary electrons in the 1 - 30 eV range. Dissociative ionization (DI) is one of the electron collision processes that can damage the DNA, either directly by causing a DNA lesion, or indirectly by producing radicals and cations that attack the DNA. To understand this process, we have developed a theoretical model for DI. Our model makes use of the fact that electron motion is much faster than nuclear motion and assumes DI proceeds through a two-step process. The first step is electron-impact ionization resulting in a particular state of the molecular ion in the geometry of the neutral molecule. In the second step the ion undergoes unimolecular dissociation. Thus the DI cross section sigma(sup DI)(sub a) for channel a is given by sigma(sup DI)(sub a) = sigma(sup I)(sub a) P(sub D) with sigma(sup I)(sub a) the ionization cross section of channel a and P(sub D) the dissociation probability. This model has been applied to study the DI of H2O, NH3, and CH4, with results in good agreement with experiment. The ionization cross section sigma(sup I)(sub a) was calculated using the improved binary encounter-dipole model and the unimolecular dissociation probability P(sub D) obtained by following the minimum energy path determined by the gradients and Hessians of the electronic energy with respect to the nuclear coordinates of the ion. This model is used to study the DI from the low-lying channels of benzene and pyridine to understand the different product formation in aromatic and heterocyclic molecules. DI study of the DNA base thymine is underway. Solvent effects will also be discussed.

Huo, Winifred M.↗