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Experimental and Theoretical Studies of Polycarbocyclic Compounds

Description: Part I. Diels-Alder cycloadditions of 1,2,3,4,9,9-hexachloro-1α,4α,4aα,8aβ-tetrahydro-l,4-methanonaphthalene (32) and 1,2,3,4,9,9-hexachloro-lα,4α,6,7- tetrahydro-l,4-methanonaphthalene (33) to 4-methyl- and 4-phenyl-l,2,4-triazoline-3,5-dione [MTAD and PTAD, respectively] and to N-methylmaleimide (NMM) have been studied. The structures of several of the resulting cycloadducts were determined by X-ray crystallographic methods. The observed stereoselectivity of each of these Diels-Alder reactions was further investigated via application of theoretical methods. Thus, semiempirical (AMI) and ab initio molecular orbital calculations were used to calculate relative energies. Ab initio calculations were employed to perform frontier molecular orbital analyses of diene-dienophile interactions.
Date: May 1998
Creator: Shukla, Rajesh, 1964-
Partner: UNT Libraries

Quantum symmetry and photoreactivity of azabenzenes

Description: The fundamental processes associated with a photochemical reaction are described with reference to experimental properties of azabenzenes. Consideration of both excitation and relaxation processes led to presentation of the symmetry propagator, a unifying principle which maps system fluctuations (perturbations acting on an initial state) with dissipations (transitions to different states), thus directing the energy flow along competing reactive and nonreactive pathways. A coherent picture of relaxation processes including chemical reactions was constructed with the aid of spectroscopic data. Pyrazine (1,4 diazine) possesses vibronically active modes which provide an efficient mechanism for internal conversion to the first excited singlet state, where other promoting modes of the correct symmetry induce both intersystem crossing to the triplet manifold, isomerization through diaza-benzvalene, and chemical reactions through cycloreversion of dewar pyrazine to yield HCN plus an azete. At higher energies simple H atom loss and internal conversion become more predominant, leading to ring opening followed by elimination of methylene nitrile and ground state reaction products. Efficiency of chemical transformations as dissipation mechanisms versus competing fluorescence, phosphorescence and radiationless relaxation was mapped from near ultraviolet to far ultraviolet by photodissociation quantum yields into reaction channels characterized by molecular beam photofragment translational spectroscopy. A reaction path model for azabenzene photochemistry was presented and tested against experiment. Presence of undiscovered channels in other azabenzene systems was predicted and verified. The dominant process, HCN elimination, was resolved into three distinct channels. Both molecular and atomic hydrogen elimination was observed, the former with significant vibrational excitation. Small yields of isomerization products, acetylene and N2, were also observed.
Date: June 1995
Creator: Chesko, J. D. M.
Partner: UNT Libraries Government Documents Department

N-Heterocyclic Carbenes of the Late Transition Metals: A Computational and Structural Database Study

Description: A computational chemistry analysis combined with a crystallographic database study of the bonding in late transition metal N-heterocyclic carbene (NHC) complexes is reported. The results illustrate a metal-carbon bond for these complexes, approximately 4% shorter than that of a M-C single bond found in metal alkyl complexes. As a consequence of this result, two hypotheses are investigated. The first hypothesis explores the possibility of multiple-bond character in the metal-carbon linkage of the NHC complex, and the second, considers the change in the hybridization of the carbenoid carbon to incorporate more p character. The latter hypothesis is supported by the results. Analysis of these complexes using the natural bond orbital method evinces NHC ligands possessing trans influence.
Date: May 2005
Creator: Baba, Eduard
Partner: UNT Libraries

Mobile Order Theory as Applied to Polycyclic Aromatic Heterocycles

Description: Experimental mole fraction solubilities of benzil, thianthrene, trans-stilbene, thioxanthen-9-one, diphenyl sulfone and dibenzothiophene sulfone are determined in pure noncomplexing and complexing solvents. Predicted solubility values are calculated for benzil, thianthrene, trans-stilbene and thioxanthen-9-one using expressions derived from Mobile Order theory. Large deviations between experimental and predicted solubilities in alcohol solvents exist, therefore optimized solute - solvent association constants are determined. Previously measured thianthrene solubilities in five binary alkane + cyclohexane solvent mixtures are compared with values predicted from Mobile Order theory using the measured solubility in each of the pure solvents as input parameters. The experimental mole fraction solubility of benzil in eight binary alcohol + 1-octanol solvent mixtures are also measured and compared with predicted values.
Date: August 1997
Creator: Fletcher, Kristin A.
Partner: UNT Libraries

Synthesis and Characterization of 2,3-Dichloropyrrolo[1,2-a]benzimidazol-1-one and Its Methylthiol Derivatives

Description: Condensation of 2,3-dichloromaleic anhydride and o-phenylenediamine in refluxing toluene affords the three compounds 2,3-dichloro-N-o-C6H4(NH2)maleimide (1), N,N¢-o-C6H4-bis(2,3-dichloromaleimide) (2), and 2,3-dichloropyrrolo[1,2-a]benzimidazol-1-one (3), with compound 1 as the major product. Repeating the same reaction in the presence of added PTSA furnishes compound 3 as the major product. Treatment of 3 with methylthiol in the presence of pyridine affords monosulfide compounds 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one (4) and and the disulfide derivatives 2,3-di(methylthio)pyrrolo[1,2-a]benzimidazol-1-one (5). The substitution of the first chlorine group in compound 3 occurs regioselectively at C-3 to produce compound 4, followed by replacement of the remaining chlorine group to furnish the disulfide compounds 5. The new compounds 1-5 have been isolated by column chromatography and characterized by IR, NMR, XRD, CV and etc.
Date: May 2006
Creator: Wu, Guanmin
Partner: UNT Libraries

[Photochemistry of intermolecular C-H bond activation reactions]. Progress report, [September 15, 1994--March 15, 1995]

Description: Since the last progress report (March 15, 1994), attention was paid to the solution photochemistry of (HBPz*{sub 3})Rh(CO){sub 2} (Pz* = 3,5-dimethylpyrazolyl) at different excitation wavelengths and in various hydrocarbon solvents (n-pentane). Absolute quantum efficiencies were obtained for the intermolecular C-H bond activation at different wavelengths and temperatures. Results indicate that there are two excited states with different reactivities and two reaction channels. The intermediate that is highly reactive toward hydrocarbon C-H bonds is probably the monocarbonyl (HBPz*{sub 3})Rh(CO) species. Related studies are being carried out on tungsten(IV) eight-coordinate-chelate complexes.
Date: December 15, 1994
Creator: Lees, A.J.
Partner: UNT Libraries Government Documents Department

Thermodynamic properties by non-calorimetric methods. Progress report, August 1, 1988--July 31, 1989

Description: This three year research program provides a valuable complement to the experimental programs currently in progress at NIPER for the Advanced Research and Technology Development (AR and TD) and Advanced Exploration and Process Technology (AEPT) divisions of the Department of Energy. These experimental programs are focused on the calorimetric determination of thermodynamic properties of key polynuclear heteroatom-containing aromatic molecules. This project for the Office of Energy Research focuses on the non-calorimetric determination of thermodynamic properties through the extension of existing correlation methodologies and through molecular spectroscopy with statistical mechanics. The paper discusses progress in three areas: (1) Improvement of thermochemical and thermophysical property predictions via enhancement of group-contribution methods using two approaches, namely, development and improvement of group-contribution parameters via correlations involving the expanded modern thermodynamics data base and development of group-contribution parameters via molecular spectroscopy and statistical mechanics of key monocyclic organic compounds; (2) Molecular spectroscopy and statistical mechanics: equipment development and developments in interpretation and assignment of spectra; and (3) Thermophysical property correlations.
Date: December 31, 1989
Creator: Steele, W.V.; Chirico, R.D.; Collier, W.B. & Strube, M.M.
Partner: UNT Libraries Government Documents Department

Thermodynamic properties by non-calorimetric methods. Final report

Description: This research program provided a valuable complement to the experimental programs currently in progress at NIPER for the Advanced Research and Technology Development (AR and TD) and Advanced Exploration and Process Technology (AEPT) divisions of the Department of Energy. These experimental programs are focused on the calorimetric determination of thermodynamic properties of key polynuclear heteroatom-containing aromatic molecules. The project for the Office of Energy Research focused on the non-calorimetric determination of thermodynamic properties through the extension of existing correlation methodologies and through molecular spectroscopy with statistical mechanics. The paper discusses the following studies: Group-contribution approach for polycyclic aromatic hydrocarbons (naphthalene, phenanthrene, anthracene, pyrene, 3-methylphenanthrene, benzoquinolines, biphenyl/hydrogen system); Group-contribution approach for key monocyclic organic compounds; Molecular spectroscopy and statistical mechanics; and Thermophysical property correlations.
Date: December 31, 1992
Creator: Steele, W.V.; Chirico, R.D.; Collier, W.B.; Strube, M.M. & Klots, T.D.
Partner: UNT Libraries Government Documents Department

Thermal decomposition studies of 1,3,3-trinitroazetidine (TNAZ) and 1-nitroso-3,3-dinitroazetidine (NDNAZ) by simultaneous thermogravimetric modulated beam mass spectroscopy

Description: The initial results from a study of the thermal decomposition of TNAZ, TNAZ-1-{sup 15}NO{sub 2} and NDNAZ using the simultaneous thermogravimetric modulated beam mass spectrometer (STMBMS) are presented. The major products formed in the decomposition of TNAZ are NO{sub 2} and NO with slightly lesser amounts of H{sub 2}O, HCN, CO/N{sub 2}, CO{sub 2}/N{sub 2}O and NDNAZ. The major product formed in the decomposition of NDNAZ is NO with lesser amounts of H{sub 2}O, HCN, CO/N{sub 2}O. The lower molecular weight products are similar to those observed in RSFTIR and IRMPD studies conducted previously by others. However, this study has shown that the mononitroso analogue of TNAZ, NDNAZ, is an important intermediate formed during the decomposition of TNAZ. It plays an important role in determining the identity of the products formed in the decomposition of TNAZ. The temporal behaviors Of the ion signals associated with the various thermal decomposition products from TNAZ, TNAZ-1-{sup 15}NO{sub 2} and NDNAZ are also presented. The illustrate the evolution sequence of the various products that are associated with the different reaction pathways that control the decomposition of these materials. In particular, the study of the {sup 15}N-labeled sample revealed that NO{sub 2} originates from both the likely sites in the TNAZ molecule and that the cleavage of the nitramine-NO{sub 2} group precedes that of the C-NO{sub 2} cleavage, resulting in similar sequences in the formation of NO and NDNAZ also.
Date: December 1, 1995
Creator: Behrens, R., Jr. & Bulusu, S.
Partner: UNT Libraries Government Documents Department

Intramolecular energy- and electron-transfer reactions in polymetallic complexes. Annual report

Description: The complexes (tpy)Ru(II)(tpp)Co(III)(PPhEt{sub 2})H{sub 2}{sup 3+}, (NC){sub 3}Fe(II)(tpp)Co(III)(PPhEt{sub 2})H{sub 2} and (NC){sub 3}Fe(II)(tpp)Co(III)(PPh{sub 3})H{sub 2} (where tpp = 2,3,5,6-tetrakis(2{prime}-pyridyl)pyrazine), were prepared and their photochemistry studied. Reasons for the low quantum yields for H{sub 2} production are discussed briefly. A series of FeRuRh complexes is being prepared. Plans for the coming year on intramolecular energy transfer and charge separation are discussed.
Date: December 1, 1991
Creator: Peterson, J.D.
Partner: UNT Libraries Government Documents Department

A molecular architectural approach to second-order nonlinear optical materials

Description: Design and synthesis of a family of calix[4]arene-based nonlinear optical (NLO) chromophores are discussed. The calixarene chromophores are macrocyclic compounds consisting These molecules were synthesized such of four simple D-{pi}-A units bridged by methylene groups. These molecules were synthesized such that four D-n-A units of the calix[4]arene were aligned along the same direction with the calixarene in a cone conformation. These nonlinear optical super-chromophores were subsequently fabricated into covalently bound self-assembled monolayers on the surfaces of fused silica and silicon. Spectroscopic second harmonic generation (SHG) measurements were carried out to determine the absolute value of the dominant element of the nonlinear susceptibility, {Chi}{sub zzz}, and the average molecular alignment, {Psi}. We find a value of {Chi}{sub zzz}{approximately} 1.5 {times} 10{sup {minus}7} esu (60 pm/V) at a wavelength of 890 nm, and {Psi} {approximately} 36{degrees} with respect to the surface normal.
Date: September 1, 1995
Creator: Yang, Xiaoguang; McBranch, D.; Swanson, B. & Li, DeQuan
Partner: UNT Libraries Government Documents Department

New high-nitrogen energetic materials for gas generators in space ordnance

Description: High-nitrogen nitroheterocyclic energetic compounds are used as explosives, propellants, and gas generants when safe, thermally stable, cool-burning energetic materials are desired. A series of compounds are compared for sensitivity properties and calculated burn performance. Thermodynamic equilibrium calculations by NASA/Lewis rocket propellant and Blake gun propellant codes gave flame temperatures, average molecular weight, and identity of the equilibrium burn products for ambient, rocket, and gun pressure environments. These compounds were subjected to calculations both as monopropellants and as 50/50 weight ratio mixtures with ammonium nitrate (AN). Special attention was paid to calculated toxic products such as carbon monoxide and hydrogen cyanide, and how these were affected by the addition of an oxidizer AN. Several compounds were noted for further calculations of a formulation ad experimental evaluation.
Date: August 1, 1995
Creator: Campbell, M.S.; Lee, Kien-Yin & Hiskey, M.A.
Partner: UNT Libraries Government Documents Department

Synthesis of 6-Methyl-9-n-propyldibenzothiophene-4-ol ammended to 6-Methyl-9-(1-methylethyl)-dibenzothiophene-4-ol

Description: The material presented below is taken from Status Reports 15, 16 and 17 and covers the progress made toward the synthesis of the modified target molecules 9-isopropyl-4-methoxy-6 methyldibenzothiophene (13) and 9-isopropyl-6methyldibenzothiophene-4-ol (14).
Date: February 28, 1992
Creator: Available, Not
Partner: UNT Libraries Government Documents Department

Synthesis of 6-Methyl-9-n-propyldibenzothiophene-4-ol

Description: The material presented here has been described to some extent in Status Reports 12, 13, and 14 and covers the progress toward the synthesis of the modified target molecules 9-isopropyl-4-methoxy-6-methyldibenzothiophene (13) and 9-isopropyl-6-methyldibenzothiophene-4-ol (14). It is divided into three parts: (a) Dehydrogenation experiments On tetrahydrodibenzothiophene 12. (b) methoxyl methyl cleavage of 13 to 14 using boron tribromide. (c) isolation and purification of methoxydibenzothiophene 13.
Date: October 28, 1991
Creator: Available, Not
Partner: UNT Libraries Government Documents Department

The workshop on conductive polymers: Final report

Description: Reports are made by groups on: polyacetylene, polyphenylene, polyaniline, and related systems; molecular, crystallographic, and defect structures in conducting polymers; heterocyclic polymers; synthesis of new and improved conducting polymers; future applications possibilities for conducting polymers; and challenges for improved understanding of properties. (DLC)
Date: January 1, 1985
Partner: UNT Libraries Government Documents Department

Coal liquefaction process streams characterization and evaluation

Description: This study demonstrated the use of the gold tube carbonization technique and reflectance microscopy analysis for the examination of process-derived materials from direct coal liquefaction. The carbonization technique, which was applied to coal liquefaction distillation resids, yields information on the amounts of gas plus distillate, pyridine-soluble resid, and pyridine-insoluble material formed when a coal liquid sample is heated to 450{degree}C for one hour at 5000 psi in an inert atmosphere. The pyridine-insolubles then are examined by reflectance microscopy to determine the type, amount, and optical texture of isotropic and anisotropic carbon formed upon carbonization. Further development of these analytical methods as process development tools may be justified on the basis of these results.
Date: December 1, 1991
Creator: Mitchell, G.; Davis, A. (Pennsylvania State Univ., University Park, PA (United States). Energy and Fuels Research Center); Burke, F.P.; Winschel, R.A. & Brandes, S.D. (Pennsylvania State Univ., University Park, PA (United States). Energy and Fuels Research Center)
Partner: UNT Libraries Government Documents Department

Hydrodenitrogenation: An increasingly important part of catalytic hydroprocessing interlocking of thermodynamics and kinetics

Description: This report outlines a new use of thermodynamic property data. The Gibbs energies of reaction obtained from thermodynamic property measurements are used to estimate, with some success, relative reactivities for aromatic organonitrogen compounds. Calculated relative rates of reaction reproduce literature values within one power of ten. The relative rates of reaction are shown to be directly proportional to the concentration of hydrogenated species formed during hydrodenitrogenation (HDN). The production of completely saturated ring systems (overhydrogenation) in HDN reactions using conventional hydroprocessing is explained solely in terms of the thermodynamics in operation in the system. The results obtained show that the order of relative reactivity obtained is strongly dependence can account for some apparent contradictions when kinetic studies reported in the literature are compared. The results for a study of the hydroprocessing of a straight-run gas oil are reproduced in this report. The formation of anilines and the increase in indole concentration above that in the original gas oil sample are explained via the thermodynamics operating in the system.
Date: April 1, 1992
Creator: Steele, W.V. & Chirico, R.D.
Partner: UNT Libraries Government Documents Department

6-Acetyldihydrohomopterin and sepiapterin affect some GTP cyclohydrolase I's and not others

Description: The first enzyme in pteridine biosynthesis, GTP cyclohydrolase I, is a likely site for regulation of pteridine biosynthesis to occur. GTP cyclohydrolase I responds to hormonal treatment and is found altered in a variety of mice with genetically based neurological and immunological disorders. Genetic loci can greatly modify the activity of GTP cyclohydrolase: Punch mutant in Drosophila hph-1 in mouse and atypical phenylketonuria in human. This report examines the ability of Ahp and sepiapterin to alter the activity of GTP cyclohydrolase I from mouse liver, rat liver and Drosophila head. 20 refs., 2 tabs.
Date: January 1, 1988
Creator: Jacobson, K.B. & Manos, R.E.
Partner: UNT Libraries Government Documents Department

Investigation of the triplet state of chlorophylls. Technical progress report, May 1, 1978--April 30, 1979

Description: The photoexcited triplet state properties of chlorophyll dimer systems in vitro were investigated by zero-field optically detected magnetic resonance (ODMR) spectroscopy at 2/sup 0/K. Measurements of the triplet state zero-field splittings, overall triplet lifetimes, and individual spin sublevel intersystem crossing rate constants were obtained for solutions of chlorophyll a and zinc-substituted chlorophyll a and for the covalently linked dimeric derivative of pyrochlorophyllide a. The triplet state properties found for these systems are interpreted within the framework of the triplet exciton model to assess the applicability of the exciton approach in determining the geometry of chlorophyll aggregate systems and to evaluate structural features of chlorophyll systems proposed as models for in vivo chlorophyll.
Date: January 1, 1979
Creator: Clarke, R.H.
Partner: UNT Libraries Government Documents Department

Kinetics and mechanism of desulfurization and denitrogenation of coal-derived liquids. Twelfth quarterly report, March 21-June 20, 1978

Description: All the data reported previously have been reevaluated to determine the quantitative reaction network for dibenzothiophene hydrodesulfurization at about 100 atm and 300/sup 0/C. This network shows the high selectivity of the catalyst for simple hydrodesulfurization (biphenyl + H/sub 2/S formation). When methyl groups are present in the 4 and 6 positions of dibenzothiophene, the primary hydrogenation reaction is approximately as fast as the primary hydrodesulfurization reaction. Ni and Mo or Ni and W used instead of Co and Mo in the catalyst, or H/sub 2/S in the reactant mixture, also favor hydrogenation relative to hydrodesulfurization. Previous results have been evaluated in light of the recent literature to provide a new interpretation of the reaction mechanism of catalytic hydrodesulfurization on surfaces of sulfided Co-Mo/Al/sub 2/0/sub 3/. It has often been assumed that catalytic hydrodesulfurization of thiophene and related compounds proceeds via a one-point end-on adsorption involving bonding of the sulfur atom with Mo ions at an anion vacancy on the catalyst surface. This interpretation is inadequate, failing to account for deuterium-exchange results, the reactivities of benzothiophene and dibenzothiophene, and the small steric effects of methyl substituents affecting the adsorption and reaction of compounds in the thiophene, benzothiophene, and dibenzothiophene families of homologs. An alternative mechanism, presented, here, involves a multipoint adsorption of the reactant, with a C=C bond interacting with the Mo cation and the S atom of the reactant interacting with a S ion on the surface. The new mechanism accounts for the observed deuterium exchange and hydrodesulfurization reactions and is consistent with the observed steric effects.
Date: October 20, 1978
Creator: Gates, B. C.; Katzer, J. R.; Olson, J. H.; Kwart, H. & Stiles, A. B.
Partner: UNT Libraries Government Documents Department

Co-firing high sulfur coal with refuse derived fuels. Technical progress report No. 8, July 1996--August 1996

Description: The objective of this study was to examine the possible formation of chlorinated organic compounds during the combustion of blends of refuse derived fuels (RDF) and coal under conditions similar to those of an atmospheric fluidized bed combustion (AFBC) system. A series of experiments were conducted using a TGA interfaced to FTIR. Additional experiments using a tube furnace preheated to AFBC operating temperatures were also conducted. The combustion products were cryogenically trapped and analyzed with a GC/MS system. The chlorination of phenols and the condensation reactions of chlorophenols were investigated in this study. A possible mechanism for the formation of chlorinated organic compounds such as dibenzodioxins and dibenzofurans, by chlorination and condensation reactions involving phenols, was proposed.
Date: August 31, 1996
Creator: Pan, Wei-Ping; Riley, J.T. & Lloyd, W.G.
Partner: UNT Libraries Government Documents Department