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LDRD final report on chemical functionalization of oligo(hydrido)silanes, economically attractive routes to new photoresponsive materials

Description: Metathesis-catalyzed polymerizations of primary silanes were performed to generate polysilanes suitable for functionalization with a variety of side groups. Modeling was employed to predict conformations and estimate electronic properties of candidate functionalized polysilanes. Chemical functionalization of oligo(hydrido)silanes with terminal {alpha}, {omega}-dienes under free radical conditions yielded highly crosslinked, nonporous polysilane networks. Ketone reduction with oligo(hydrido)silanes under free radical conditions led to novel poly(phenylalkoxysilanes). Free radical reduction of terminal alkenyl(alkoxy)silanes forms functionalized polysilanes which can be further transformed into sol-gel matrices with the polysilane functionality intact. These gels may be processed into nonporous xerogels or high surface area aerogels.
Date: May 1, 1997
Creator: Jamison, G.M.; Loy, D.A. & Curro, J.G.
Partner: UNT Libraries Government Documents Department

Scanning tunneling microscopy studies of organic monolayers adsorbed on the rhodium(111) crystal surface

Description: Scanning Tunneling Microscopy studies were carried out on ordered overlayers on the (111) surface of rhodium. These adsorbates include carbon monoxide (CO), cyclohexane, cyclohexene, 1,4-cyclohexadiene, para-xylene, and meta-xylene. Coadsorbate systems included: CO with ethylidyne, CO with para- and meta-xylene, and para-xylene with meta-xylene. In the case of CO, the structure of the low coverage (2x2) overlayer has been observed. The symmetry of the unit cell in this layer suggests that the CO is adsorbed in the 3-fold hollow sites. There were also two higher coverage surface structures with ({radical}7x{radical}7) unit cells. One of these is composed of trimers of CO and has three CO molecules in each unit cell. The other structure has an additional CO molecule, making a total of four. This extra CO sits on a top site.
Date: August 1, 1999
Creator: Cernota, Paul D.
Partner: UNT Libraries Government Documents Department


Description: Dynamic mechanical analysis has been used to characterize the effects of tritium gas (initially 1 atm. pressure, ambient temperature) exposure over times up to 2.3 years on several thermoplastics-ultrahigh molecular weight polyethylene (UHMW-PE), polytetrafluoroethylene (PTFE), and Vespel{reg_sign} polyimide, and on several formulations of elastomers based on ethylene propylene diene monomer (EPDM). Tritium exposure stiffened the elastic modulus of UHMW-PE up to about 1 year and then softened it, and reduced the viscous response monotonically with time. PTFE initially stiffened, however the samples became too weak to handle after nine months exposure. The dynamic properties of Vespel{reg_sign} were not affected. The glass transition temperature of the EPDM formulations increased approximately 4 C. following three months tritium exposure.
Date: November 12, 2008
Creator: Clark, E
Partner: UNT Libraries Government Documents Department

Reaction mechanisms in aromatic hydrocarbon formation involving the C{sub 5}H{sub 5} cyclopentadienyl moiety

Description: The quantum chemical BAC-MP4 and BAC-MP2 methods have been used to investigate the reaction mechanisms leading to polycyclic aromatic hydrocarbon (PAH) ring formation. In particular the authors have determined the elementary reaction steps in the conversion of two cyclopentadienyl radicals to naphthalene. This reaction mechanism is shown to be an extension of the mechanism occurring in the H atom-assisted conversion of fulvene to benzene. The net reaction involves the formation of dihydrofulvalene, which eliminates a hydrogen atom and then rearranges to form naphthalene through a series of ring closures and openings. The importance of forming the {single_bond}CR({center_dot}){single_bond}CHR{single_bond}CR{prime}{double_bond}CR{double_prime}-moiety, which can undergo rearrangement to form three-carbon-atom ring structures, is illustrated with the C{sub 4}H{sub 7} system. The ability of hydrogen atoms to migrate around the cyclopentadienyl moiety is illustrated both for methyl-cyclopentadiene, C{sub 5}H{sub 5}CH{sub 3}, and dihydrofulvalene, C{sub 5}H{sub 5}C{sub 5}H{sub 5}, as well as for their radical species, C{sub 6}H{sub 7} and C{sub 5}H{sub 5}C{sub 5}H{sub 4}. The mobility of hydrogen in the cyclopentadienyl moiety plays an important role both in providing resonance-stabilized radical products and in creating the {single_bond}CR({center_dot}){single_bond}CHR{single_bond}CR{prime}{double_bond}CR{double_prime}-moiety for ring formation. The results illustrate the radical pathway for converting five-membered rings to aromatic six-membered rings. Furthermore, the results indicate the important catalytic role of H atoms in the aromatic ring formation process.
Date: February 1, 1996
Creator: Melius, C.F.; Colvin, M.E.; Marinov, N.M.; Pitz, W.J. & Senkan, S.M.
Partner: UNT Libraries Government Documents Department

Kinetics and mechanism of the oxidation of alkenes and silanes by hydrogen peroxide catalyzed by methylrhenium trioxide (MTO) and a novel application of electrospray mass spectrometry to study the hydrolysis of MTO

Description: Conjugated dienes were oxidized by hydrogen peroxide with methylrhenium trioxide (MTO) as catalyst. Methylrhenium bis-peroxide was the major reactive catalyst present. Hydroxyalkenes and trisubstituted silane were also tested. Mechanisms for each of these reactions are presented.
Date: November 8, 1999
Creator: Tan, Haisong
Partner: UNT Libraries Government Documents Department

Construction integrity assessment report (ETN-98-0005) S-Farm overground transfer (OGT) system valve pit 241-S-B to valve pit 241-S-D

Description: The S-Farm overground transfer (OGT) line will bypass the existing line(s), between valve pits 241-S-B and 241-S-D that no longer meet system requirements. The new OGT line will provide a waste transfer pipeline between these valve pits in support of saltwell pumping activities. The length of the OGT line is approximately 180 ft from pit to pit. The primary pipe is nominal 1-in. diameter stainless steel (SST) braided Ethylene-propylene Diene Monomer (EPDM) hose. The encasement pipe is a nominal 3-in., flanged, SST pipe made up of several different length pipe spool pieces (drawing H-2-829564, sh. 1 and sh. 2). The OGT line slopes from valve pit 241-S-B toward valve pit 241-S-D. At each end, the primary and encasement pipe connect to a pit entry spool piece. The pit entry spool pieces are constructed of prefabricated SST materials. These spool pieces allow for the separation of the primary and encasement pipelines after the pipes have entered the valve pits (drawing H-2-818280, sh. 2). The pit entry spool pieces also allow for leak detection of the encasement pipe at each end (drawing H-2-829564, sh. 2). The OGT encasement pipeline is supported above ground by adjustable height unistrut brackets and precast concrete bases (drawing H-2-829654, sh. 1). The pipeline is heat-traced and insulated. The heat tracing and insulation supply and retain latent heat that prevents waste solidification during transfers and provides freeze protection. The total length of the pipeline is above ground, thereby negating the need for cathodic corrosion protection. This Construction Integrity Assessment Report (CIAR) is prepared by Fluor Daniel Northwest for Numatec Hanford Corporation/Lockheed Martin Hanford Corporation, the operations contractor, and the U. S. Department of Energy, the system owner. The CIAR is intended to verify that construction was performed in accordance with the provisions of Washington Administrative Code, WAC-173-303-640 (3) ...
Date: August 12, 1999
Creator: HICKS, D.F.
Partner: UNT Libraries Government Documents Department

The Stereoselective Formation of Bicyclic Enamines with Bridgehead Unsaturation via Tandem C-H Bond Activation/Alkenylation/Electrocyclization

Description: Rhodium-catalyzed intermolecular C-H activation of {alpha}, {beta}-unsaturated imines in the presence of alkynes leads to a tandem process in which coupling to the alkyne occurs at the {beta}-C-H bond of the imine, followed by electrocyclization of the resulting azatriene intermediates to give dihydropyridines (eq 1). Consideration of the intramolecular version of this overall transformation (Scheme 1) raises interesting regiochemical issues. For example in a compound such as 1, where the nitrogen and alkyne are connected by a 4-carbon tether, the presumed first-formed hydrido(vinyl)rhodium function can add to the triple bond in a 1,2-fashion, producing complex 2 with a new endocyclic double bond. Alternatively, addition might occur in a 2,1-fashion, leading to product 4 with an exocyclic double bond. We now wish to report that this intramolecular cyclization occurs smoothly at 100 C, and the exocyclic double bond route is exclusively followed. Remarkably, products such as 4 do not resist further cyclization. Even though both the transition state for this process and the resulting product are presumably strained, the overall transformation leads to good yields of unusual bridgehead doubly-bonded enamines such as 5. The unique chemistry of conjugated enamine 5 is consistent with the increased strain of this molecule as well as with inhibited conjugation between the nitrogen lone pair and the adjacent double bond (vida infra). We began our investigation into the C-H activation/cyclization of alkyne-tethered imine 1 by extensive screening of transition metal catalysts for this process. Rhodium-based catalysts were found to be the most efficient (Table 1), leading exclusively to the bridgehead dienamine; none of the catalysts that were employed in the screening led to quinolizidine 3 or to the product of intramolecular Diels-Alder reaction. The optimized reaction conditions employ the electron-rich monophosphine ligand (p-NMe{sub 2})PhPEt{sub 2} in 1:1 ratio relative to the metal (entry 6). Other phosphine ...
Date: December 10, 2007
Creator: Ellman, Jonathan A.; Yotphan, Sirilata & Bergman, Robert
Partner: UNT Libraries Government Documents Department


Description: This report documents test results for the exposure of four formulations of EPDM (ethylene-propylene diene monomer) elastomer to tritium gas at one atmosphere for approximately one week and characterization of material property changes and changes to the exposure gas during exposure. All EPDM samples were provided by Los Alamos National Laboratory (LANL). Material properties that were characterized include mass, sample dimensions, appearance, flexibility, and dynamic mechanical properties. The glass transition temperature was determined by analysis of the dynamic mechanical property data per ASTM standards. No change of glass transition temperature due to the short tritium gas exposure was observed. Filled and unfilled formulations of Dupont{reg_sign} Nordel{trademark} 1440 had a slightly higher glass transition temperature than filled and unfilled formulations of Uniroyal{reg_sign} Royalene{reg_sign} 580H; filled formulations had the same glass transition as unfilled. The exposed samples appeared the same as before exposure--there was no evidence of discoloration, and no residue on stainless steel spacers contacting the samples during exposure was observed. The exposed samples remained flexible--all formulations passed a break test without failing. The unique properties of polymers make them ideal for certain components in gas handling systems. Specifically, the resiliency of elastomers is ideal for sealing surfaces, for example in valves. EPDM, initially developed in the 1960s, is a hydrocarbon polymer used extensively for sealing applications. EPDM is used for its excellent combination of properties including high/low-temperature resistance, radiation resistance, aging resistance, and good mechanical properties. This report summarizes initial work to characterize effects of tritium gas exposure on samples of four types of EPDM elastomer: graphite filled and unfilled formulations of Nordel{trademark} 1440 and Royalene{reg_sign} 580H.
Date: June 7, 2007
Creator: Clark, E
Partner: UNT Libraries Government Documents Department

Gas-Phase Oxidation of Cm+ and Cm2+ -- Thermodynamics of neutral and ionized CmO

Description: Fourier transform ion cyclotron resonance mass spectrometry was employed to study the products and kinetics of gas-phase reactions of Cm+ and Cm2+; parallel studies were carried out with La+/2+, Gd+/2+ and Lu+/2+. Reactions with oxygen-donor molecules provided estimates for the bond dissociation energies, D[M+-O](M = Cm, Gd, Lu). The first ionization energy, IE[CmO], was obtained from the reactivity of CmO+ with dienes, and the second ionization energies, IE[MO+](M = Cm, La, Gd, Lu), from the rates of electron-transfer reactions from neutrals to the MO2+ ions. The following thermodynamic quantities for curium oxide molecules were obtained: IE[CmO]= 6.4+-0.2 eV; IE[CmO+]= 15.8+-0.4 eV; D[Cm-O]= 710+-45 kJ mol-1; D[Cm+-O]= 670+-40 kJ mol-1; and D[Cm2+-O]= 342+-55 kJ mol-1. Estimates for the M2+-O bond energies for M = Cm, La, Gd and Lu are all intermediate between D[N2-O]and D[OC-O]--i.e., 167 kJ mol-1< D[M2+-O]< 532 kJ mol-1 -- such that the four MO2+ ions fulfill the thermodynamic requirement for catalytic O-atom transport from N2O to CO. It was demonstrated that the kinetics are also favorable and that the CmO2+, LaO2+, GdO2+ and LuO2+ dipositive ions each catalyze the gas-phase oxidation of CO to CO2 by N2O. The CmO2+ ion appeared during the reaction of Cm+ with O2 when the intermediate, CmO+, was not collisionally cooled -- although its formation is kinetically and/or thermodynamically unfavorable, CmO2+ is a stable species.
Date: December 8, 2008
Creator: Gibson, John K; Haire, Richard G.; Santos, Marta; Pires de Matos, Antonio & Marcalo, Joaquim
Partner: UNT Libraries Government Documents Department

Coal/Polymer Coprocessing With Efficient Use of Hydrogen

Description: The final project period was devoted to investigating the binary mixture pyrolysis of polypropylene and polystyrene. Their interactions were assessed in order to provide a baseline for experiments with multicomponent mixtures of polymers with coal. Pyrolysis of polypropylene, polystyrene and their binary mixture was investigated at temperatures of 350 C and 420 C with reaction times from 1 to 180 minutes. Two different loadings, 10 mg and 20 mg, were studied for neat polypropylene and polystyrene to assess the effect of total pressure on product yields and selectivities. For neat pyrolysis of polypropylene, total conversion was much higher at 420 C, and no significant effect of loading on the total conversion was observed. Four classes of products, alkanes, alkenes, dienes, and aromatic compounds, were observed, and their distribution was explained by a typical free radical mechanism. For neat polystyrene pyrolysis, conversion reached approximately 75% at 350 C, while at 420 C the conversion reached a maximum around 90% at 10 minutes and decreased at longer times because of condensation reactions. The selectivities to major products were slightly different for the two different loadings due to the effect of total reaction pressure on secondary reactions. For binary mixture pyrolysis, the overall conversion was higher than the average of the two neat cases. The conversion of polystyrene remained the same, but a significant enhancement in the polypropylene conversion was observed. This suggests that the less reactive polypropylene was initiated by polystyrene-derived radicals. These results are summarized in detail in an attached manuscript that is currently in preparation. The other results obtained during the lifetime of this grant are documented in the set of attached manuscripts.
Date: September 30, 2000
Creator: Broadbelt, Linda J.; DeWitt, Matthew J. & Wong, Hsi-Wu
Partner: UNT Libraries Government Documents Department

Species differences in metabolism of 1,3-butadiene

Description: 1,3-Butadiene (BD) is a 4-carbon gaseous compound with two double bonds. Used in high tonnage to make styrene-butadiene polymers in the rubber industry. Because of large amounts in use, BD was tested for toxicity in 2-year inhalation exposures of both Sprague-Dawley rats and B6C3F{sub 1} mice. The results of the two-species studies were dramatically different. In the initial study in mice, BD was shown to be a potent multiple-site carcinogen at exposure levels of 625 and 1250 ppM. There were increased incidences of neoplasia in the heart, lung, mammary gland, and ovary; malignant lymphomas resulted in early deaths of the mice so that the planned 2-year study was stopped after only 61 weeks of exposure. The second study in mice was conducted at much lower exposure concentrations (6.25, 20, 62.5, 200, and 625 ppM) and lasted 104 weeks. Increased incidences of hemangiosarcomas of the heart and lung neoplasia were observed in males exposed to 62.5 ppM BD, while females had increased lung neoplasia even at the 6.25 ppM exposure level. Early deaths from lymphomas were again observed at the high exposure concentration (625 ppm). A noncancer toxicity observed in mice was a macrocytic, megaloblastic anemia.
Date: February 1, 1995
Creator: Henderson, R. F.
Partner: UNT Libraries Government Documents Department

Transformations of toluene radical cation in ZSM-5 and Silicalite

Description: Toluene radical cations produced by {gamma} irradiation at 77 K in ZSM-5 and Silicalite (isomorphous with ZSM-5 but nonpolar) undergo a reversible transformation to the norbornadiene radical cation at temperatures {le}150K. The transformation occurs to a greater extent in the more polar zeolite (ZSM-5). The substrate concentration plays an important role. Toluene radical cations undergo ion-molecule reactions to give benzyl radicals at low substrate loading at temperatures >200 K. At higher concentration, different adsorption sites become populated which allow the transformation to norbornadiene radical cation to take place.
Date: November 25, 1992
Creator: Barnabas, M. V.; Werst, D. W. & Trifunac, A. D.
Partner: UNT Libraries Government Documents Department

[Synthetic and mechanistic investigation of olefin polymerization catalyzed by early transition metal compounds]. Progress report, Second year, 1 April 1992--31 March 1992

Description: During the second year we continued to prepare and characterize organoyttrium and organoscandium compounds for use as catalysts for polymerizing simple olefins and diolefins. Simple, one-component systems are being pursued, suitable for chain initiation, propagation, and termination studies. This document is divided into: dicarbollide derivatives of scandium as potential catalysts; design, synthesis, and characterization of the first isospecific {alpha} olefin polymerization catalysts; polymerization of {alpha} olefins and 1,5- hexadiene using organoscandium catalysts; and attempted preparations of diastereomeric Nb and Ta olefin/hydride and olefin/alkyl derivatives.
Date: August 1, 1993
Creator: Bercaw, J. E.
Partner: UNT Libraries Government Documents Department


Description: This is an interim status report for tasks carried out per Task Technical Plan SRNL-STI-2011-00506. A series of tasks/experiments are being performed at the Savannah River National Laboratory to monitor the aging performance of ethylene propylene diene monomer (EPDM) Orings used in the H1616 shipping package. The data will support the technical basis to extend the annual maintenance of the EPDM O-rings in the H1616 shipping package and to predict the life of the seals at bounding service conditions. Current expectations are that the O-rings will maintain a seal at bounding normal temperatures in service (152 F) for at least 12 months. The baseline aging data review suggests that the EPDM O-rings are likely to retain significant mechanical properties and sealing force at bounding service temperatures to provide a service life of at least 2 years. At lower, more realistic temperatures, longer service life is likely. Parallel compression stress relaxation and vessel leak test efforts are in progress to further validate this assessment and quantify a more realistic service life prediction. The H1616 shipping package O-rings were evaluated for baseline property data as part of this test program. This was done to provide a basis for comparison of changes in material properties and performance parameters as a function of aging. This initial characterization was limited to physical and mechanical properties, namely hardness, thickness and tensile strength. These properties appear to be consistent with O-ring specifications. Three H1616-1 Containment Vessels were placed in test conditions and are aging at temperatures ranging from 160 to 300 F. The vessels were Helium leak-tested initially and have been tested at periodic intervals after cooling to room temperature to determine if they meet the criterion of leaktightness defined in ANSI standard N14.5-97 (< 1E-07 std cc air/sec at room temperature). To date, no leak test ...
Date: August 31, 2012
Creator: Stefek, T.; Daugherty, W. & Skidmore, E.
Partner: UNT Libraries Government Documents Department

Chemical conversions in supercritical media: Environmentally sound approaches to processes and materials

Description: This is the final report of a two-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The aim of this effort was to evaluate the potential of supercritical fluids (SCF) as reaction media in an effort to develop new, environmentally-friendly methods for chemical synthesis or processing. The use of novel media creates the possibility of opening up substantially different chemical pathways, increasing selectivity (eliminating waste by-products), and enhancing reaction rates (decreasing hold-up times and saving energy). In addition, the use of SCF as reaction media facilitates downstream separations and mitigate or eliminate the need for hazardous solvents on scales from bench top to production. This project employed a highly interdisciplinary approach to investigate the utility of SCFs as reaction media for polymer synthesis and synthetic organic chemistry.
Date: July 1, 1996
Creator: Burns, C.; Borkowsky, S.; Buelow, S.; Langlois, D.; LeLacheur, R.; Mitchell, M. et al.
Partner: UNT Libraries Government Documents Department

Dynamics of H sub 2 elimination from unsaturated hydrocarbons

Description: State-of-the-art laser and molecular beam techniques are used to study the dynamics of H{sub 2} elimination from 1,4-cyclohexadiene and ethylene. Information on the transition state configurations and the dynamics of the dissociation processes for these reactions is reported. 152 refs., 54 figs., 12 tabs.
Date: February 1, 1991
Creator: Cromwell, E.F.
Partner: UNT Libraries Government Documents Department

Ultrafast spectroscopic studies of the photophysics of phenyl- substituted butadienes in liquids

Description: The transient absorption decay times of tetraphenylbutadiene (TPB) and tetraphenylmethylbutadiene (TPMB) are measured as a function of solvent viscosity and of probe wavelength. The TPB spectra suggest that after excitation, TPB relaxes to the bottom of the excited state well where it relaxes radiatively to the ground state surface. TPMB transient absorption spectra taken using different probe wavelengths decay on different timescales. 71 refs., 38 figs., 6 tabs.
Date: August 1, 1991
Creator: Hoff, R.L.
Partner: UNT Libraries Government Documents Department

Production of super-smooth articles

Description: Super-smooth rounded or formed articles made of thermoplastic materials including various poly(methyl methacrylate) or acrylonitrile-butadiene-styrene copolymers are produced by immersing the articles into a bath, the composition of which is slowly changed with time. The starting composition of the bath is made up of at least one solvent for the polymer and a diluent made up of at least one nonsolvent for the polymer and optional materials which are soluble in the bath. The resulting extremely smooth articles are useful as mandrels for laser fusion and should be useful for a wide variety of other purposes, for example lenses.
Date: May 29, 1981
Creator: Duchane, D.V.
Partner: UNT Libraries Government Documents Department

[Synthetic and mechanistic investigation of olefin polymerization catalyzed by early transition metal compounds]

Description: During the second year we continued to prepare and characterize organoyttrium and organoscandium compounds for use as catalysts for polymerizing simple olefins and diolefins. Simple, one-component systems are being pursued, suitable for chain initiation, propagation, and termination studies. This document is divided into: dicarbollide derivatives of scandium as potential catalysts; design, synthesis, and characterization of the first isospecific [alpha] olefin polymerization catalysts; polymerization of [alpha] olefins and 1,5- hexadiene using organoscandium catalysts; and attempted preparations of diastereomeric Nb and Ta olefin/hydride and olefin/alkyl derivatives.
Date: January 1, 1993
Creator: Bercaw, J.E.
Partner: UNT Libraries Government Documents Department

Photochemistry of 1 and 2-(2-methylphenyl)-1,6-heptadiene. [4a-methyl-1,2,3,4,4a,9,10,10a-octahydrophenanthrene]

Description: In an attempt to synthesize partially saturated phenanthrene derivatives by an intramolecular Diels-Alder reaction between a photochemically produced o-xylylene (diene) and a tethered dienophile, it was found that 1 and 2 underwent a photochemically allowed (2 + 2) cycloaddition. Irradiation of 1 gave 6-(2-methylphenyl)bicyclo(3.2.0)heptane in 86% yield. Upon irradiation of 2, a benzvalene rearrangement of 2 first took place, producing the meta isomer 2-(3-methylphenyl)-1,6-heptadiene, followed by a (2 + 2) photocycloaddition giving 1-(3-methylphenyl)bicyclo(3.2.0)heptane in 15% yield. Direct irradiation of 2-(3-methylphenyl)-1,6-heptadiene gave the same bicyclo derivative as 2 in 34% yield. Examination of the fluorescence spectra of 1 and 2 in comparison with 1-(2-methylphenyl)propene and 2-(2-methylphenyl)-1-butene, respectively, has shown that 1 may be biased toward (2 + 2) cycloaddition where 2 is not biased toward (2 + 2) photocycloization. Attempts to produce 4a-methyl-1,2,3,4,4a,9,10,10a-octahydrophenanthrene by an intramolecular Diels-Alder reaction of the o-xylylene produced by irradiation of 3 will also be described.
Date: January 1, 1982
Creator: Barrows, R.D. & Hornback, J.M.
Partner: UNT Libraries Government Documents Department

Sensitization and quenching in the conversion of light energy into chemical energy. Progress report, February 1, 1980-January 31, 1981

Description: Extensive data from Stern-Volmer, Lamola-Hammond, and Ilenda-Daughenbaugh-Cristol quenching kinetics have now been accumulated on photosolvolysis in t-butyl alcohol for benzyl chloride and a number of meta and para substituted benzyl chlorides. Evidence for the existence of two triplet states, one relatively short-lived (tau 0-2 nsec) which gives solvolysis product and a second, relatively long-lived (tau 5-26 nsec), which does not give product, but instead is energy wasting, has been accumulated. The system, p-acetobenzyl chloride, has been investigated in detail. A method for quenching of singlet states for measurement of singlet lifetimes in the 100 picosecond to nanosecond range is being developed. Preliminary work on benzyl acetate photosolvolysis has been conducted. Some work on the goemetrical requirements for intra-molecular excitation transfer in bichromophoric molecules has been conducted. Several dienes related to norbornadiene have been prepared and preparative photoisomerizations to quadricyclene analogues have been carried out. Considerable attention has been given to certain di-..pi..-methane rearrangements, work on most of which is still in progress. One system, the ethyl ester of dibenzobarrelene-7-carboxylic acid, has been scrutinized in detail.
Date: September 1, 1980
Creator: Cristol, S.J.
Partner: UNT Libraries Government Documents Department

Diosmacycloalkanes as models for the formation of hydrocarbons from surface methylenes. Progress report, November 1, 1992--October 31, 1993

Description: The report is divided into: vibrational models for surface ethylidenes (on catalyst surfaces); alpha vs beta hydrogen elimination in formation of propene from an osmacyclobutane; mechanism of formation and fragmentation of diosmacyclobutanes; reaction of dienes and allenes with diosmacyclobutanes; structure of Os(CO){sub 4}(C{sub 2}H{sub 4}), an osmacyclopropane; and reaction of {mu}-oxobis [(trifluoromethanesulfanato) (phenyl)iodine(III)] with Group 14 propargyl derivatives and a propargyl ether. 16 refs, figs.
Date: May 1, 1993
Creator: Norton, J. R.
Partner: UNT Libraries Government Documents Department

Synthesis and chemistry of yttrium and lanthanide metal complexes

Description: The objective of this research project is to determine the special features of complexes of yttrium and the lanthanide metals which will allow the design and synthesis of materials with unique chemical, physical, and catalytic properties. Past studies of yttrium and lanthanide metal alkyl and hydride complexes stabilized by cyclopentadienyl co-ligands have shown that a substantial, often singular, organometallic chemistry is available via these metals. More extensive utilization of the chemical opportunities available through yttrium and the lanthanides would be possible, however, if stabilizing ancillary ligand systems less sensitive to oxidation and protonolysis than cyclopentadienides could be developed. Alkoxide ligands are attractive in this regard and our recent research had focused on alkoxides and the special opportunities they can provide to these metals. 6 refs., 10 figs.
Date: September 1, 1991
Creator: Evans, W.J.
Partner: UNT Libraries Government Documents Department

Organic photochemical storage of solar energy. Progress report, March 1, 1978-January 31, 1979

Description: Photosensitization mechanisms for driving energy storing reactions of readily available organic compounds have been studied. Aromatic sensitizers were used as complexing agents for a series of non-conjugated dienes which are capable of valence isomerization. Diene exciplexes, shown to be stabilized by electron donor-acceptor interaction, led to photoisomers with high chemical and quantum efficiency in two of the cases studied. For other systems, sensitizer-diene photoaddition reactions were observed. Exciplex isomerization of quadricyclanes and hexamethyldewarbenzene was studied. Factors determining the efficiency of rearrangement of excited complexes were examined including the role of exciplex excitation energy in controlling the novel adiabatic exciplex isomerization of hexamethyldewarbenzene. With triplet photosensitizers visible light (to 520 nm) was used to bring about an energy storing valence isomerization of a diester derivative of norbornadiene. High quantum yields (0.6) were measured at the longest wavelengths yet utilized for this type of isomerization. The quantum efficiency for isomerization using a very low energy triplet sensitizer was significantly enhanced at slightly elevated temperatures, suggesting that thermal energy (in amounts present in solar collector media) can be an aid in driving energy storing photo-reactions.
Date: February 1, 1979
Creator: Jones, G. II
Partner: UNT Libraries Government Documents Department