Sites of Reactivity During Ligand-Exchange Reactions in Octahedral Group VIB Metal Carbonyls (open access)

Sites of Reactivity During Ligand-Exchange Reactions in Octahedral Group VIB Metal Carbonyls

The site of initial metal-carbonyl bond-breaking during ligand-exchange reactions in a series of octahedral metal carbonyls of the type (L2)M(CO)4 (M = Cr, Mo, W; L2 = diphos, phen, dipy) has been determined employing infrared spectroscopy and Fourier transform nuclear magnetic resonance spectroscopy. The results of this study reveal, for all metal carbonyl complexes of the type mentioned above, that loss of CO occurs exclusively at an axial position (cis to the bidentate ligand, I^)• The dynamic nature of the five-coordinate intermediates, such as (diphos)Mo(CO)3, (phen)M(CO)3 (M = Cr, Mo, W), and (dipy)Cr(CO)3, which are generated in solution upon CO dissociation, is reported and discussed. The results of this investigation confirm that these intermediates are fluxional on the time scale of CO-exchange process. A mechanism which describes the site of initial metal-carbonyl bond-breaking and the fluxionality of the five-coordinate intermediate during ligand-exchange reactions in the complexes (L2)M(CO)4 is proposed. A kinetic study of reactions of W(CO)6 with pseudo-halide anions (NCS-, NCO-, CN-) has been initiated. The results indicate that these reactions proceed via a bimolecular path, which involves initial attack of the pseudo-halide anion at a carbonyl carbon of W(CO)6,
Date: December 1979
Creator: Asali, Khalil Jamil
System: The UNT Digital Library
The Photolysis of Ethyllithium and Triethylaluminum (open access)

The Photolysis of Ethyllithium and Triethylaluminum

The majority of interest in organolithium and organoaluminum compounds has centered around their potency as polymerization catalysts.
Date: January 1970
Creator: Brewer, Terry Lowell
System: The UNT Digital Library
Structure-Activity Studies of Halopyrethroids (open access)

Structure-Activity Studies of Halopyrethroids

The structures of the new pyrethroids were elucidated utilizing nuclear magnetic spectroscopy and elemental analysis. The biological activity of the pyrethroids has been evaluated for houseflies and yellow fever mosquitoes. A correlation of increase in rapid knockdown and toxicity with decrease in size of halogen has been made. The most effective compound, the difluorovinyl ester, has a toxicity of 123 times greater than pyrethrins. This degree of toxicity has not previously been reported for a 5-benzyl-3-furanmethyl ester. The relative lipophilicities of the dihalovinyl esters, Rm, have been determined by reverse phase partition chromatography. The R values for the dihalo esters correlate with their m effectiveness as rapid knockdown agents. The least lipophilic compound, the difluorovinyl ester, possessed the highest knockdown in this dihalovinyl ester series. The difluorovinyl ester has incorporated a high level of toxicity while maintaining excellent effectiveness as a knockdown agent against houseflies. This combination of high knockdown and high toxicity in a single compound has not been previously reported. Several other pyrethroids were synthesized and evaluated for knockdown and toxicity, in order to make specific comparisons with pyrethroids of known effectiveness. The replacement of the isobutenyl group of the chrysanthemates by the dihalovinyl group has been effective …
Date: December 1974
Creator: Brown, Dale Gordon
System: The UNT Digital Library
Infrared Studies of Group VIB metal Carbonyl Derivatives (open access)

Infrared Studies of Group VIB metal Carbonyl Derivatives

With three different proposals for the bonding in metal carbonyls, it was decided to look into the situation more thoroughly in order to see what other evidence was available to support or refute any of these ideas. It became obvious that a definite contradiction existed between the kinetic evidence of various metal carbonyls, and the concept of MC bond strengths as predicted by Cotton's theory.
Date: August 1971
Creator: Brown, Richard Arthur
System: The UNT Digital Library
The Chlorination of Amino Acid in Municipal Waste Effluents (open access)

The Chlorination of Amino Acid in Municipal Waste Effluents

In model reaction systems to test amino acids in chlorinated waste effluents, several amino acids were chlorinated at high chlorine doses. (2000-4000 mg/1). Amino acids present in municipal waste effluents before and after chlorination were concentrated and purified using cation exchange and Chelex resins. After concentration and cleanup of the samples, the amino acids were derivatized by esterification of the acid functional groups and acylation of the amine groups. Identification and quantification of the amino acids and chlorination products was carried out by gas chromatography/mass spectrometry, using a digital computer data system. Analysis of the waste products revealed the presence of new carbon-chlorine bonded derivatives of the amino acid tyrosine when the effluents were treated with heavy doses of chlorine.
Date: July 1977
Creator: Burleson, Jimmie L.
System: The UNT Digital Library
Magnetic Properties of Oxovanadium(IV) Complexes of Substituted N-(Hydroxylalkyl) Salicylideneimines (open access)

Magnetic Properties of Oxovanadium(IV) Complexes of Substituted N-(Hydroxylalkyl) Salicylideneimines

A series of oxovanadium(IV) complexes of Schiff bases derived from substituted salicylaldehyde and aminoalcohols has been prepared and characterized. The Schiff bases coordinate through 0, N, and 0 as tridentate bivalent ligands. The primary purpose of the investigation is to describe the structure and bonding in these complexes. The subnormal magnetic properties of the complexes provide much information about both the structure and the bonding in the complexes.
Date: May 1972
Creator: Carey, Elbert Franklin
System: The UNT Digital Library
Electric Dichroism Spectroscopy in the Vacuum Ultraviolet (open access)

Electric Dichroism Spectroscopy in the Vacuum Ultraviolet

When a molecule, which possess a permanent dipole moment is exposed to an intense electric field, its absorption spectrum may be altered. These alterations are manifest as shifts in energy and as changes in band shape and intensity. The electric dichroism of absorption bands can be used to probe the excited state that is formed when a molecule undergoes a transition. The properties that may be investigated include transition polarization, excited state dipole moment and mean polarizability, and field-induced mixing of symmetrically equivalent excited states. The theoretical model and experimental devices that have been developed to determine these properties are presented and discussed. The data, taken in total, and its combination with other existing evidence, adds credence to the assignment of the second excited singlet of aldehydes and ketones to be extravalent, accompanied by relatively large delocalization of electronic charge, and polarized in-planiie and perpendicularly to the C-0 axis.
Date: May 1978
Creator: Causley, Gary C.
System: The UNT Digital Library
Syntheses of Antimetabolites (open access)

Syntheses of Antimetabolites

In these studies several different types of antimetabolites were synthesized, and their biological effects were examined in various assay systems. More extensive investigations were done in microbial systems in which many of the compounds proved to be inhibitory to growth, and attempts were made to determine the mode of biochemical action by adding supplements of the appropriate natural metabolite.
Date: January 1970
Creator: Clifton, George Gil
System: The UNT Digital Library
Chemical Cleavage of Human Phosphoglucose Isomerase at Cysteine (open access)

Chemical Cleavage of Human Phosphoglucose Isomerase at Cysteine

The present study has resulted in the development of a procedure for the specific chemical fragmentation of human phosphoglucose isomerase into a minimal number of peptides. A two-cycle procedure for cleaving the protein with 2-nitro-5- thiocyanobenzoic acid results in four primary peptides and three overlap peptides. The peptides can be readily separated on the basis of their size by using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Preliminary peptide alignments have been considered, and amino acid analyses have been performed. End-terminal analyses of the enzyme revealed a carboxyl terminal sequence of Asp-Val-Gln and a blocked amino terminus. The cysteine cleavage procedure provides an excellent method for the identification and location of specific genetic mutations of human phosphoglucose isomerase.
Date: December 1975
Creator: Conn, Worth R.
System: The UNT Digital Library
Ketene Carbodiimide Cycloadditions (open access)

Ketene Carbodiimide Cycloadditions

It was proposed to study the cycloaddition of ketenes and carbodiimides in some detail. The first objective was to investigate the general applicability of the reaction as a tool for the synthetic organic chemist in the preparation of a new class of substituted β-lactams; i.e., imino-β-lactams. It was proposed for this part of the research problem to look for the intermediate, either directly or indirectly, by trapping experiments. It was further proposed to study substituent effects in the ketene and carbodiimide and also Investigate the effect of solvent polarity on the reaction rate. From these data, it was hoped that the mechanism of the cycloaddition reaction could be elucidated.
Date: August 1970
Creator: Dorsey, Edwin Darrell
System: The UNT Digital Library
Bonding Studies in Group IV Substituted n,n-dimethylanilines (open access)

Bonding Studies in Group IV Substituted n,n-dimethylanilines

The purpose of the present work is to study the effects of the trimethylsilyl and trimethylgermyl substituents on the N,N-dimethylamino ring system. Both ground and excited state interactions were studied and their magnitudes determined. The experimental data were then used in conjunction with molecular orbital calculations to differentiate among, and determine the importance of, d-p bonding, hyperconjugation or polarization of the trimethylsilyl group on the ground and excited state bonding.
Date: December 1971
Creator: Drews, Michael James
System: The UNT Digital Library
The Crystal and Molecular Structures of Tri-(p-Fluorophenyl)-Amine and Tri-(p-Iodophenyl)-Amine (open access)

The Crystal and Molecular Structures of Tri-(p-Fluorophenyl)-Amine and Tri-(p-Iodophenyl)-Amine

Because of the need for data on the geometry of nitrogen in arylamines, the determination of the crystal and molecular structures of tri-(p-fluorophenyl)-amine (TFPA) and tri-(p-iodophenyl)-amine (TIPA) was undertaken as the subject of this dissertation.
Date: January 1970
Creator: Freeman, Gerald R. (Gerald Richard)
System: The UNT Digital Library
The Electrochemical Reduction of Methyl Vinyl Ketone in Aqueous Solutions (open access)

The Electrochemical Reduction of Methyl Vinyl Ketone in Aqueous Solutions

This work is an in-depth study of a system with an approach designed to determine the electrode processes and the factors or conditions which control them.
Date: January 1970
Creator: French, Eddie Carroll
System: The UNT Digital Library
Studies Concerning the Production of Lactobacillic Acid in Lactobacillus Plantarum (open access)

Studies Concerning the Production of Lactobacillic Acid in Lactobacillus Plantarum

This study is concerned with certain factors affecting the content of lactobacillic acid in Lactobacillus plantarum. Three main areas of investigation are reported herein. The effects of both the oxygen tension and the pH of the culture medium on the accumulation of lactobacillic acid were determined. In addition, monolayer studies were conducted to determine the influence of cyclopropane fatty acid content on the molecular packing of membrane lipids.
Date: May 1973
Creator: Halper, Laura Ann
System: The UNT Digital Library
The Recombination Rate Coefficient of Molecular Helium Ions in a Pulsed Afterglow at 1.86 Torr (open access)

The Recombination Rate Coefficient of Molecular Helium Ions in a Pulsed Afterglow at 1.86 Torr

The recombination rate coefficient for molecular helium ions has been measured in a pulsed afterglow at 1.86 Torr as a function of electron temperature and electron density without making a priori assumptions about the functional dependence. The concentrations of the molecular ions and electrons were measured and the source terms for the molecular ions were included in the rate equation.
Date: August 1972
Creator: Hicks, Helen Segrave
System: The UNT Digital Library
Rearrangement of Alkylhaloketene-Cyclopentadiene Adducts in Basic Solution--A New Synthesis of 2-Alkyltropones (open access)

Rearrangement of Alkylhaloketene-Cyclopentadiene Adducts in Basic Solution--A New Synthesis of 2-Alkyltropones

This research is concerned with determining whether the previously reported synthesis of tropolone by the solvolysis of the dichloroketene-cyclopentadiene adduct in sodium acetate and acetic acid could be used to prepare 2-alkyltropones from the adducts of alkylhaloketenes and cyclopentadiene. The information obtained from these rearrangements could be useful in determining the mechanism of the ring expansion of halogenated ketene-cyclopentadiene adducts to tropone derivatives.
Date: December 1971
Creator: Hieble, Jacob Paul, 1948-
System: The UNT Digital Library
Magnetic Properties of Metal(II) Schiff Base Complexes (open access)

Magnetic Properties of Metal(II) Schiff Base Complexes

Ligands prepared from various combinations of aldehydes and ketones with the appropriate aminealcohol were complexed with cupric acetate monohydrate. The complexes with O,NO or N,N,O donor atoms were synthesized to study the influences of the ligand on molecular structure, spin-spin interaction, and on the value of the exchange integral. The magnetic data indicated that of the eight Cu(II) complexes discussed, two behaved differently from known analogous compounds. Cu (benzoylacetone :ethanolamine) was compared to Cu(acac:ethanolamine), and Cu(pyrr:oaminophenol) was compared to Cu(acac:o-aminophenol). Each pair of complexes was postulated to have the same molecular structure. The synthesis and characterization of Mn(pyrr:oaminophenol) 2H2 is also discussed. The following physical data were collected and discussed: elemental analysis, melting point, molecular weight, infrared spectra, electronic spectra, and magnetic susceptibility.
Date: May 1976
Creator: Hines, Mary Katherine
System: The UNT Digital Library
Aldohaloketenes and the Stereochemistry of Aldohaloketene Cycloadditions (open access)

Aldohaloketenes and the Stereochemistry of Aldohaloketene Cycloadditions

The objective of this research problem was to synthesize aldohaloketenes and investigate the chemistry of this new class of ketenes.
Date: May 1970
Creator: Hoff, Edwin Frank
System: The UNT Digital Library
Synthesis of 1-Amino-2-Hydroxycyclopentanecarboxylic Acid (open access)

Synthesis of 1-Amino-2-Hydroxycyclopentanecarboxylic Acid

This investigation involved the synthesis of 1-amino-2-hydroxycyclopentanecarboxylic acid, a potential structural analog of the natural amino acids, serine and threonine. The title compound also includes the structural features present in an established antitumor agent, cycloleucine.
Date: December 1970
Creator: Huddle, John David
System: The UNT Digital Library
Kinetic Studies and Vibrational Spectra of Disubstituted Metal Carbonyls (open access)

Kinetic Studies and Vibrational Spectra of Disubstituted Metal Carbonyls

The oxidative elimination reactions of (5-X-phen)Mo(C0)₄ (X = H, CH₃, Cl, NO₂; phen = o-phenanthroline) and (3,4,7,8-(CH₃)₄-phen)Mo(CO)₄ with mercuric chloride in acetone have been investigated. In these reactions, a carbon monoxide group is replaced by two univalent ligands, accompanied by the corresponding increase in coordination number and formal oxidation state of the central metal atom, to give products of the type, (X-phen)Mo(CO)₃(Cl)HgCl. With the exception of (3,4,7,8-(CH₃)₄-phen), the substituted o-phenanthrolines were selected so as to minimize steric differences from one substrate to another while obtaining the widest range of pKₐ of the ligand.
Date: May 1972
Creator: Jernigan, Robert Thorne
System: The UNT Digital Library
Reactions of N-(Substituted) Phthalimides with n-Alkylamines (open access)

Reactions of N-(Substituted) Phthalimides with n-Alkylamines

The initial purpose of this study was to determine if steric problems would account for the difference in the products obtained in the reaction of the N-(substituted)phthalimide with low and high molecular weight amines.
Date: August 1970
Creator: Johnson, D. Pat
System: The UNT Digital Library
Magnetic Properties of Copper (II) Complexes of Schiff Bases (open access)

Magnetic Properties of Copper (II) Complexes of Schiff Bases

The synthesis and characterization of two new Schiff base copper(II) complexes are reported. These are Cu(acac: 2-amino-l-phenylethanol) and Cu(acac:2-amino-l-butanol). The ligands, derived from acetylacetone and the appropriate aminoalcohol, are dibasic tridentates with 0,N,O donor atoms. The magnetic properties of the complexes were studied at several temperatures between 78 OK and 296 OK. The magnetic moment of Cu(acac:2-amino-l-phenylethanol) varied little with temperature, and that of Cu(acac:2-amino-lbutanol) increased as the temperature was lowered. This is in contrast to the magnetic moment of Cu(acac:ethanolamine), which decreases as the temperature decreases. Molecular weight data, infrared spectra, magnetic data, electronic spectra, and electron spin resonance spectra of both complexes are reported and discussed.
Date: August 1975
Creator: Jones, William James
System: The UNT Digital Library
Hyperconjugative Interactions in Silylanilines (open access)

Hyperconjugative Interactions in Silylanilines

The purpose of the present work is to study the bonding interactions between the substituents and the ring π system for a series of ortho and para MeₙH₃₋ₙM (M = C or Si, n = 0-3) substituted N,N-dimethylaniline . Both ground and excited-state interactions were studied and their magnitudes determined. The experimental data were then used in conjunction with molecular orbital calculations to differentiate among inductive, hyperconjugative, and d-pπ interactions on the ground and excited states. Overall, the study indicates that d orbital involvement in the interactions of organosilicon substituents with unsaturated systems is much less significant than is generally held. The importance of pₛᵢ⁻π and pₛᵢ⁻π* hyperconjugative interactions between silicon σ* orbitals and π system in producing the effects of silicon substitution on unsaturated systems has become more apparent.
Date: May 1975
Creator: Jung, Il Nam
System: The UNT Digital Library
Electrochemical Dissolution of  ZnO Single Crystals (open access)

Electrochemical Dissolution of ZnO Single Crystals

The separation of oxidation-reduction reactions into individual half-cells with a resulting "mixed potential" is well known as a dissolution mechanism for metals; however, the mechanism by which non-conducting crystals lose ions to the solution has been studied only slightly.
Date: January 1970
Creator: Justice, David Dixon
System: The UNT Digital Library