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Electrophilic metal alkyl chemistry in new ligand environments

Description: Cationic group 4 and actinide Cp{sub 2}MR{sup +} metallocenes, and isolobal neutral group 3 and lanthanide Cp{sub 2}MR analogs, are exceptionally reactive in insertion and {sigma}-bond metathesis processes, and have been exploited extensively in catalysis and synthesis, most notably single-site olefin polymerization. The objectives of recent work were to design new electrophilic metal alkyls based on non-Cp{sub 2}M structures, and to exploit these systems in fundamental and applied studies related to olefin polymerization and other catalytic reactions. Key results are reported in the following areas: discrete non-metallocene cationic group 4 alkyls, activation of non-metallocene compounds with methylalumoxane, and cationic aluminum alkyl compounds. Numerous structural formulas are included.
Date: September 11, 2002
Creator: Jordan, Richard F.
Partner: UNT Libraries Government Documents Department

LDRD final report on new homogeneous catalysts for direct olefin epoxidation (LDRD 52591).

Description: This report summarizes our findings during the study of a novel homogeneous epoxidation catalyst system that uses molecular oxygen as the oxidant, a ''Holy Grail'' in catalysis. While olefins (alkenes) that do not contain allylic hydrogens can be epoxidized directly using heterogeneous catalysts, most olefins cannot, and so a general, atom-efficient route is desired. While most of the work performed on this LDRD has been on pincer complexes of late transition metals, we also scouted out metal/ligand combinations that were significantly different, and unfortunately, less successful. Most of the work reported here deals with phosphorus-ligated Pd hydrides [(PCP)Pd-H]. We have demonstrated that molecular oxygen gas can insert into the Pd-H bond, giving a structurally characterized Pd-OOH species. This species reacts with oxygen acceptors such as olefins to donate an oxygen atom, although in various levels of selectivity, and to generate a [(PCP)Pd-OH] molecule. We discovered that the active [(PCP)Pd-H] active catalyst can be regenerated by addition of either CO or hydrogen. The demonstration of each step of the catalytic cycle is quite significant. Extensions to the pincer-Pd chemistry by attaching a fluorinated tail to the pincer designed to be used in solvents with higher oxygen solubilities are also presented.
Date: February 1, 2006
Creator: Goldberg, Karen (University of Washington); Smythe, Nicole A. (University of Washington); Moore, Joshua T.; Stewart, Constantine A.; Kemp, Richard Alan; Miller, James Edward et al.
Partner: UNT Libraries Government Documents Department

Asymmetric Synthesis of (-)-Incarvillateine Employing an Intramolecular Alkylation via Rh-Catalyzed Olefinic C-H Bond Activation

Description: An asymmetric total synthesis of (-)-incarvillateine, a natural product having potent analgesic properties, has been achieved in 11 steps and 15.4% overall yield. The key step is a rhodium-catalyzed intramolecular alkylation of an olefinic C-H bond to set two stereocenters. Additionally, this transformation produces an exocyclic, tetrasubstituted alkene through which the bicyclic piperidine moiety can readily be accessed.
Date: February 18, 2008
Creator: Tsai, Andy; Bergman, Robert & Ellman, Jonathan
Partner: UNT Libraries Government Documents Department

Asymmetric Intramolecular Alkylation of Chiral Aromatic Imines via Catalytic C-H Bond Activation

Description: The asymmetric intramolecular alkylation of chiral aromatic aldimines, in which differentially substituted alkenes are tethered meta to the imine, was investigated. High enantioselectivities were obtained for imines prepared from aminoindane derivatives, which function as directing groups for the rhodium-catalyzed C-H bond activation. Initial demonstration of catalytic asymmetric intramolecular alkylation also was achieved by employing a sterically hindered achiral imine substrate and catalytic amounts of a chiral amine.
Date: April 16, 2007
Creator: Watzke, Anja; Wilson, Rebecca; O'Malley, Steven; Bergman, Robert & Ellman, Jonathan
Partner: UNT Libraries Government Documents Department

Low Severity Coal Liquefaction Promoted by Cyclic Olefins

Description: The development of the donor solvent technology for coal liquefaction has drawn a good deal of attention over the last three decades. The search for better hydrogen donors led investigators to a class of compounds known as cyclic olefins. Cyclic olefins are analogues of the conventional hydroaromatic donor species but do not contain aromatic rings. The cyclic olefins are highly reactive compounds which readily release their hydrogen at temperatures of 200 C or higher. Considerable effort has been o expended toward understanding the process of hydrogen donation. Most of this work was conducted in bomb reactors, with product analysis being carried out after the reaction was complete. Efforts directed towards fundamental studies of these reactions in situ are rare. The current work employs a high temperature and high pressure infrared cell to monitor in situ the concentrations of reactants and products during hydrogen release from hydrogen donor compounds.
Date: April 9, 1998
Creator: Curtis, Christine W.
Partner: UNT Libraries Government Documents Department

A description of NUEXS, an upgrade of the code FCUP used to compute proton recoil current from CH{sub 2} foils

Description: A computer code, FCUP, developed by A. Craft computes currents of recoil protons from a time- and energy-dependent neutron flux striking a CH{sub 2} foil. Three problem areas need to be addressed to extend the code`s usefulness. First, FCUP computes a response that is not time dependent; that is, only the input time bin is broadened to account for the finite time distribution of protons from a single neutron energy; second, the time coordinate of the signal predicted is translated arbitrarily rather than absolutely relative to the time of maximum neutron production in the source; and third, the code does not account for electron pickup by protons at low proton energies in the target and absorber foils. This report describes the changes in calculational method used to overcome these problems.
Date: August 1, 1982
Creator: Stelts, M.L. & Wood, B.E.
Partner: UNT Libraries Government Documents Department

[Energies of organic compounds]

Description: The enthalpy of reduction of lactones to the corresponding diols has been determined, allowing the enthaipies of formation of the lactones to be determined. Results of this study agree well with data obtained for enthalpies of hydrolysis of the lactones. We have begun the measurement of the enthalpies of reduction of norbornanones, and we have shown that it is possible to determine the difference in energy between the exo and endo forms of the product alcohols by measuring the equilibrium constant as a function of temperature. The study of the enthalpies of hydration of carbonyl compounds has continued, and the enthalpies of hydrolysis of the corresponding ketals is being determined. The study of the enthalpies of hydration of alkenes is nearly completed, and the rearrangement reactions which were uncovered are being investigated.
Date: December 31, 1991
Creator: Wiberg, K.B.
Partner: UNT Libraries Government Documents Department


Description: "Ultrasene" typically contained 57 wt % branched paraffins and cycloparaffins, 40 wt% n-paraffins, 3 wt% aromatics, and less than 0.1 wt% olefins. The n-paraffinic fraction from "Ultrasene" was stable to chemical and radiolytic degradation, whereas the combined branched paraffinic and cycloparaffinic fraction, and the aromatic fraction, were significantly less stable. (auth)
Date: June 1, 1961
Creator: West, D. L.
Partner: UNT Libraries Government Documents Department

A Well-Defined, Silica-Supported Tungsten Imido Alkylidene OlefinMetathesis Catalyst

Description: The reaction of [W(=NAr)(=CHtBu)(CH2tBu)2](1; Ar =2,6-iPrC6H3) with a silica partially dehydroxylated at 700oC, SiO2-(700),gives syn-[(_SiO)W(=NAr)(=CHtBu)(CH2tBu)](2) as a major surface species,which was fully characterized by mass balance analysis, IR, NMR, EXAFS,and DFT periodic calculations. Similarly, complex 1 reacts with[(c-C5H9)7Si7O12SiOH]to give [(SiO)W(=NAr)(=CHtBu)(CH2tBu)](2m), whichshows similar spectroscopic properties. Surface complex 2 is a highlyactive propene metathesis catalyst, which can achieve a TON of 16000within 100 h, with only a slow deactivation.
Date: June 13, 2006
Creator: Rhers, Bochra; Salameh, Alain; Baudouin, Anne; Quadrelli, ElsjeA.; Taoufik, Mostafa; Coperet, Christophe et al.
Partner: UNT Libraries Government Documents Department

Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C-H Bond Activation

Description: Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe){sub 2}]{sub 2} and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.
Date: May 22, 2008
Creator: Harada, Hitoshi; Thalji, Reema; Bergman, Robert & Ellman, Jonathan
Partner: UNT Libraries Government Documents Department


Description: Using a reactor in which the coal is physically separated from the solid catalyst by a porous wall permeable to the hydrogen donor solvent, it was shown that direct contact between the catalyst and the coal is not required for catalyzed coal liquefaction. This occurs however only when there is a hydrogen atmosphere, as liquefaction with catalyst participation does not occur in a nitrogen atmosphere. Liquefaction by hydrogen transfer from the donor solvent itself does occur. This suggests that there is transfer of hydrogen from the catalyst to the coal via the solvent. The character of the solvent makes a significant difference, the better solvents being good hydrogen donors. These results indicate that the role of the catalyst may be to regenerate the spent hydrogen donor solvent during the liquefaction process. The peak temperature for volatiles evolution has been shown to be a reproducible measure of the coal rank. This was shown by an excellent correlation (R2 = 0.998) between peak volatiles temperatures (by TGA) and vitrinite reflectance. Using TG/MS, the volatiles contents of coals of a wide range of ranks was determined. The low rank coals emit largely phenols and some other oxygen compounds and olefins. The higher rank coals emit largely aromatic hydrocarbons and some olefins.
Date: January 1, 2000
Creator: Klein, Michael T.
Partner: UNT Libraries Government Documents Department

[Energies of organic compounds]

Description: The first part of our study of the enthalpy of reduction of carbonyl compounds has been completed and includes four aldehydes, acetone, a series of cyclic ketones and ethyl acetate. Results suggest that some of the literature data for these compounds are significantly in error. Equilibrium constants have been measured for the reaction of carbonyl compounds with water to give hydrates as well as with methanol to give either hemiacetals or acetals. They cover a wide range, and studies are underway to determine the reasons for the differences. Studies of the enthalpies of hydration of some alkenes which yield tertiary alcohols have been completed, as well as a study of the hydrolysis of lactones. The ``gauche effect`` has been studied, and has been shown to result from the formation of bent bonds when atoms of much different electronegativity are joined.
Date: July 1, 1995
Partner: UNT Libraries Government Documents Department

Separating Mechanical and Chemical Contributions to Molecular-Level Friction

Description: The authors use force-probe microscopy to study the friction force and the adhesive interaction for molecular monolayer self-assembled on both Au probe tips and substrate surfaces. By systematically varying the chemical nature of the end groups on these monolayers the authors have, for the first time, delineated the mechanical and chemical origins of molecular-level friction. They use chemically inert {double_bond}CH{sub 3} groups on both interracial surfaces to establish the purely mechanical component of the friction and contrast the results with the findings for chemically active {double_bond}COOH end-groups. In addition, by using odd or even numbers of methylene groups in the alkyl backbones of the molecules they are able to determine the levels of inter-film and intra-film hydrogen bonding.
Date: August 14, 2000
Partner: UNT Libraries Government Documents Department


Description: Ozone levels observed during a field campaign in Houston were significantly higher than that observed in Phoenix or Philadelphia. An examination of the slope of O{sub x} versus NO{sub z} in the urban plumes shows that NO{sub x} is used 2 to 3 times more efficiently in Houston as compared with Phoenix and Philadelphia. Representative values of OPEx are 7-12, 3, and 4, in Houston, Phoenix, and Philadelphia. Aircraft observations have been used to calculate P(O{sub 3})/P(NO{sub z}). Values in Houston are significantly higher than in Phoenix and Philadelphia. We show that P(O{sub 3})/P(NO{sub z}) is proportional to a VOC/NO{sub 2}-OH reactivity ratio. High values of P(O{sub 3})/P(NO{sub z}) in Houston are due to emissions of reactive olefins from the ship channel region. It is significant that high values of P(O{sub 3})/P(NO{sub z}) occur at NO{sub x} levels up to several 10's of ppb. Not only is the chemistry efficient but it will be long lasting. The occurrence of high NO{sub x} and high OPEx is fostered by the co-location of VOC and NO{sub x} sources in the Houston industrial areas.
Date: September 17, 2001
Creator: KLEINMAN,L.
Partner: UNT Libraries Government Documents Department

Ozone chemiluminescent detection of olefins: Potential applications for real-time measurements of natural hydrocarbon emissions

Description: A chemiluminescence analyzer has been constructed that takes advantage of the temperature dependence of the ozone-hydrocarbon reaction. When operated at a temperature of 170 C, the analyzer functions as a total nonmethane hydrocarbon analyzer with sensitivities 10--1,000 times better than a conventional FID. However, with operation at varying temperatures, the chemiluminescent signal reflects the differences in rates of reaction of the hydrocarbons with ozone. Preliminary studies at room temperature indicated that the relative rates of reaction of isoprene, {alpha}-pinene, {beta}-pinene, and limonene with ozone correlated with the observed chemiluminescence signal. When hydrocarbons are grouped in classes of similar structure, their rates of reaction with electrophilic atmospheric oxidants (e.g., OH, O{sub 3}, NO{sub 3}) can be correlated with each other. By varying the temperature of the reaction chamber, the chemiluminescence analyzer can be tuned to more reactive classes of hydrocarbons. Therefore, the chemiluminescence analyzer has the ability to determine atmospheric hydrocarbon concentrations as a function of class and will also provide a measure of the atmospheric reactivity of the hydrocarbons.
Date: October 1, 1997
Creator: Marley, N.A.; Gaffney, J.S. & Cunningham, M.M.
Partner: UNT Libraries Government Documents Department

Ion kinetics and thermochemistry pertinent to mass spectrometric organic speciation. Progress report, November 15, 1992--14 November 1995

Description: Essentially all of the completed/in progress studies during the last contract period have involved the NIST HPMS unit. Three distinct areas of in-house research are recognizable: (i) determinations of binding energies and entropies for association and cluster ions, which is accomplished by measuring the temperature dependence of the appropriate equilibrium, (ii) measurement of the temperature dependence unimolecular and bimolecular rate constants, and (iii) evaluation of PA`s, HA`s, and IP`s via measurement of variable-temperature equilibria of the type AH{sup +} + B {leftrightarrow} BH{sup +} + A, A{sup -} + BH {leftrightarrow} AH + B{sup -}, and A{sup +} + B {leftrightarrow} B+ + A. Key results from some representative projects are summarized below.
Date: May 1, 1998
Creator: Sieck, L.W.
Partner: UNT Libraries Government Documents Department

Energies of organic compounds

Description: The studies included hydrolysis of ketals, hydration of alkenes, barrier to rotation about C-O bonds in esters and acids, hydrolysis of lactones, reduction of ketones, non-bonded interactions, and enthalpies of vaporization of ketones, ketals, and other compounds.
Date: July 1, 1995
Creator: Wiberg, K.B.
Partner: UNT Libraries Government Documents Department

Perfluorinated quaternary ammonium salts of polyoxometalate anions: Fluorous biphasic oxidation catalysis with and without fluorous solvents

Description: Perfluorinated quaternary ammonium cations, [CF{sub 3}(CF{sub 2}){sub 7}(CH{sub 2}){sub 3}]{sub 3}CH{sub 3}N{sup +} (RFN{sup +}), were synthesized and used as counter cations for the [WZnM{sub 2}(H{sub 2}O){sub 2}(ZnW{sub 9}O{sub 34}){sub 2}]{sup 12-} (M = Mn(II), Zn(II)), polyoxometalate. The (RFN{sup +}){sub 12}[WZnM{sub 2}(H{sub 2}O){sub 2}(ZnW9O{sub 34}){sub 2}] compounds were fluorous biphasic catalysts for alcohol and alkenol oxidation, and alkene epoxidation with aqueous hydrogen peroxide. Reaction protocols with or without a fluorous solvent were tested. The catalytic activity and selectivity was affected both by the hydrophobicity of the solvent and the substrate.
Date: May 28, 2003
Creator: Maayan, Galia; Fish, Richard H. & Neumann, Ronny
Partner: UNT Libraries Government Documents Department

An Investigation of Model Catalyzed Hydrocarbon Formation Reactions

Description: Work was focused on two areas aimed at understanding the chemistry of realistic catalytic systems: (1) The synthesis and characterization of model supported olefin metathesis catalysts. (2) Understanding the role of the carbonaceous layer present on Pd(111) single crystal model catalysts during reaction.
Date: May 2, 2001
Creator: Tysoe, W. T.
Partner: UNT Libraries Government Documents Department

Energies of organic compounds. Technical progress report

Description: A procedure was developed for carbonyl group reduction using triethylborohydride. Esters and lactones are readily reduced and are suitable as substrates. Some enthalpies of hydrolysis of lactones and esters were measured. Heats of trifluoroacetolysis of alkenes leading to tertiary alcohols were measured; some cyclic systems were also investigated. In order to study the effect of {alpha}-alkyl substituents on ketones, rotational barriers adjacent to carbonyl groups were studied.
Date: August 12, 1987
Creator: Wiberg, K.B.
Partner: UNT Libraries Government Documents Department