Browsing by Author "Zingaro, Ralph A."

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    Binary phosphorus selenides: The reaction of phosphorus pentaselenide with alcohols
    (1967) Kudchadker, Mohan Vaikunth; Zingaro, Ralph A.; Eubank, P. T.; Ham, Joe S.; Meyers, Edward A.; Pearson, Karl H.
    The preparations of tetraphosphorus triselenide, P₄Se₃, and phosphorus pentaselenide, P₂Se₅ were investigated. A simple method was developed for the synthesis of P₄Se₃ in a very pure state. An optimum set of conditions was established to obtain P₂Se₅ in a state of high reactivity. The reaction of P₂Se₅ with a number of aliphatic alcohols was investigated and the general course of the reaction was established. The following compounds were isolated and characterized: (1) Potassium 0,0'-diethyldiselenophosphate, (2) Potassium 0,0'-di-n-propyldiselenophosphate, (3) Potassium 0,0'-di-n-butyldiselenophosphate, (4) Potassium 0,0'-di-n-amyldiselenophosphate monohydrate, (5) Potassium 0,0'-dicyclohexyldiselenophosphate, (6) Bis(0,0'-diethyldiselenophosphato)selenium(II), (7) Bis(0,0'-diisopropyldiselenophosphat)e, (8) Bis(0,0'-dicyclohexyldiselenophosphate), (9) Tris(0,0'-diethyldiselenophosphato)chromium(III), (10) Tris(0,0'-di-n-propyldiselenophosphato)chromium(III). The properties of these compounds were measured by means of infrared, ultraviolet and MNR spectroscopic and differential thermal analysis.
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    Biomolecules containing the SAsR₂ functional group : a chemical and carcinostatic study
    (1980) Mitchell, Cheryl Ruth; Zingaro, Ralph A.; Bates, G. W.; Hall, M. B.; Meyers, Edward A.
    Thio sugar and thio steroid esters of several dialkylarsinous acids have been prepared and characterized. Specifically, the syntheses of the following compounds have been investigated: 1-thio-2,3:5,6-di-O-isopropylidene mannofuranose; 1-S-dialkylarsino-1-thio-2,3:5,6-di-O-isopropylidene-mannofuranoside, (alkyl = methyl, ethyl, propyl, and butyl); 6-thio-1,2,3,4-tetra-O-acetyl-mannopyranoside; 6-S-alkylarsino-6-thio-1,2,3,4-tetra-O-acetyl-mannopyranoside, (alkyl = methyl, ethyl, propyl, and butyl); 3-thio-dehydroisoandrosterone; 3-S-dialkylarsino-3-thio-dehydroisoandrosterone, (alkyl = methyl, ethyl, propyl, and butyl); Pregn-4-ene-1,16-dithio-21-acetyl-3,11,20 trione; Pregna-1,4-diene-16-S-dialkylarsino-16-thio-21-acetyl-3,11,20-trione, (alkyl = methyl, ethyl); 24-thio-lanosterol; 24-S-dialkylarsino-24-thio lanosterol, (alkyl = methyl, ethyl). Attempted preparations are also reported for 17-S-dialkylarsino-17-thio-testosterone and 17-S-dialkylarsino-17-thio-cortisone acetate. The [^1}H NMR spectrum of these compounds may be interpreted in a manner consistent with the proposed structures. [^13]C NMR spectra were reported and used to elucidate the structure of the dehydroisoandrosterol. The mass spectra of the compounds are reported...
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    Compounds and methods for the treatment of cancer
    (United States. Patent and Trademark Office, 2008-07-29) Zingaro, Ralph A.; Duzkale, Hatice; Freireich, Emil J.; Kantarjian, Hagop; Sotelo-lerma, Merida; Verstovsek, Srdan; Gao, Mingzhang; The Texas A&M University System; Board of Regents, The University of Texas System
    The present invention provides organic arsenicals. Many of these compounds have potent in vitro cytotoxic activity against numerous human tumor cell lines, both of solid and hematological origin, as well as against malignant blood cells from patients with leukemia.
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    Compounds and methods for the treatment of cancer
    (United States. Patent and Trademark Office, 2012-07-17) Zingaro, Ralph A.; Zingaro, Ralph A.; The Texas A&M University System
    The present invention provides organic arsenicals which may be used to treat numerous human tumor cell lines, both of solid and hematological origin, as well as against malignant blood cells from patients with leukemia.
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    A continuous-lumped phase-equilibrium model for complex multiphase reactions
    (1988) Moore, Patrick Kevin; Anthony, Rayford G.; Akgerman, Aydin; Eubank, Philip T.; Hanson, Daniel T.; Zingaro, Ralph A.
    The accurate prediction of phase equilibrium is vital to the modeling of many complex, multiphase reaction mixtures. Phase-equilibrium calculations for such mixtures often become computationally intensive due to the large number of components in the mixture. Furthermore, such mixtures are frequently described by approximate analyses such as incompletely resolved chromatograms. Before phase-equilibrium calculations can be performed, these analyses must be parameterized, or "lumped." The number of parameters resulting from the lumping process should, in general, be kept as small as possible to minimize the computer time required for the subsequent calculations. A new lumping technique, "continuous lumping," which is especially suited for complex mixtures described by chromatographic data, has been developed. The continuous-lumping method can be considered as an extension of pseudocomponent lumping, which treats the mixture as if it were composed of only a few components, or it can be considered as a generalization of continuous-mixture methods, which treat the mixture as a continuum of components. The continuous-lumping method uses a functional formulation similar to the continuous-mixture method but is based mathematically on the original discrete mixture. This mathematical formalism allows for the evaluation of the errors involved in the lumping process and for the direct incorporation of individual component properties into the continuous-lumping method. In this study, the continuous-lumping method is formally developed from the original discrete equations describing the mixture. The method is then compared to the pseudocomponent method using a simple calculation assuming Raoult's Law. A generalized phase-equilibrium program is then developed using the continuous-lumping method with piecewise-linear basis functions and the Soave modification of the Redlich-Kwong equation-of-state. The resulting program provides a general means for calculating high-pressure phase equilibria for complex mixtures of industrial significance.
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    The effect of selenium on the lipids of two unicellular marine algae
    (1983) Gennity, Joseph Michae; Wood, Randall; Gunn, J. Martyn; Pettigrew, Donald W.; Zingaro, Ralph A.
    The incorporation of selenium into the lipids of two unicellular marine algae has been investigated. Axenic cultures of the green algae Dunaliella primolecta and the red algae Porphyridium crueutum were grown in the presence of sublethal quantities of selenium (10ppm) as selenite. Both algae were found to contain selenium bound to all purified lipids, except for saturated hydrocarbons. Of the lipids which contain selenium, carotenoid pigments show the greatest selenium concentration ((beta)-carotene: 1.3(mu)gSe/mg lipid; zeaxanthin: 1.1 (mu)gSe/mg lipid) in both algae. P. cruentum contains about ten times as much lipid-associated selenium as D. primolecta, even though the lipids of both algae were very similar. This selenium has been shown to be incorporated non-metabolically into the lipid molecule. The lipid-associated selenium is probably non-covalently bound to the lipid molecule and may interact with double bonds. Selenite does not affect the lipid composition of D. primolecta, as compared with algae grown in the absence of added selenium. A selenium-induced 40% decrease in the cell content of eicosapentaenoic acid (20:5(omega)3) and 20% decrease in arachidonic acid (20:4(omega)6) in polar lipids (glycolipids plus phospholipids) was observed in P. cruentum. A 25% decrease in the chlorophyll (alpha) content of this red algae also occurred. The cell content of other fatty acids, phospholipids and glycolipids was unaltered by selenium. These results are consistent with a selenite-induced oxidation of P. cruentum lipids. The presence of glutathione peroxidase was not demonstrated in either algae. However, a non-enzymatic, glutathione-dependent activity capable of reducing H(,2)O(,2) and t-butyl hydroperoxide was present in both algae. This activity was attributable to endogenous algal antioxidants such as ascorbate. Selenite induces a doubling of this activity. This increase is probably due to the presence of selenium compounds which are also antioxidants. Selenium is therefore able to increase the antioxidant potential of algal cells. However, no in vivo selenium-induced protection of algal lipids from oxidation was apparent.
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    Electrochemical investigations in aqueous and nonaqueous solvents Part I: Polarographic diffusion coefficients. Part II: Electrochemical investigation of gadolinium
    (1968) Fritsche, Herbert Ahart; Jones, Jerry L.; Duller, Nelson M.; Gladden, J. K.; Sicilio, Fred; Zingaro, Ralph A.
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    Electron paramagnetic resonance studies of valence tautomer anion radicals and ion-pairing in semiquinones
    (1968) Owens, Robert Marion; Hancock, C. Kinney; Traxler, Ralph N.; Meinke, W. W.; Meyer, Edward A.; Prescott, J. M.; Zingaro, Ralph A.
    The epr spectral parameters of the monohomocyclooctatetraene anion radical (XXXV) have been found to be relatively insensitive to changes in solvent, temperature, and counterion. The similar geometry of the anion radical, XXXV, and the monohomocyclooctatetraene dianion (XXXVI) is noted. A disproportionation equilibrium between XXXVI, XXXV, and cis-fused bicycle(6.1.0)nona-2,4,6-triene (XXXIV) is apparent. For the systems studied, the anion radical XXXV is favored over any of its valence tautomeric forms. The anion radicals formed during the alkali metal reduction of XXXIV in liquid ammonia have been investigated. Potassium metal reduction of XXXIV in liquid ammonia produced solutions of the anion radical, XXXV. Similar results were obtained from the potassium reduction of cis-fused bicycle(6.1.0)nona-2,4,6-triene-9.9'-d₂ (XLV) in liquid ammonia. In contrast, lithium or sodium reduction of XXXIV in liquid ammonia produced diamagnetic solution of XXXIV in liquid ammonia produced diamagnetic solutions which upon warming to +25� produced the methylcyclooctatetraene anion radical (XI. I). Similar reductions of XLV in liquid ammonia produced solutions of the anion radical, R₂, whose structure is not known. The anion radicals formed during the electrolytic and alkali metal reductions of bullvalene (VIII) have been investigated. Alkali metal reduction (lithium, sodium, or potassium) of VIII in DME and THF produced solutions of the naphthalene anion radical (XV). Within experimental error the formation of LIV and XV in the systems studied is not due to impurities present in VIII. Temperature dependent epr studies have been conducted on semiquinones produced by alkali metal reduction (lithium, sodium, or potassium) of octahydro-9, 10-anthraquinone (LV) and 2.6-dimethylbenzoquinone (LVIII) in DME, THF, and liquid ammonia. Ion-pairs exhibiting different degrees of association have been observed, the degree of association depending on the temperature, solvent, counterion, and mode of anion radical formation. The results demonstrate a marked perturbation of the spin density distribution, in the respective quinoidal systems studied, as a consequence of ion-pair association between the semiquinone and alkali metal cation. Certain of the systems studied exhibited line width alternation phenomena. Possible mechanisms to explain the observed line width phenomena are discussed.
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    An electron paramagnetic resonance study of flavin anion radicals
    Winters, James Curtis; Sicilio, Fred; Ashcraft, Allan C.; Laane, Jaan; Zingaro, Ralph A.
    The electron paramagnetic resonance spectra of lumiflavin (LF), Flavin mononucleotide (FMN), and riboflavin (RF) anion radicals in alkaline aqueous solutions of sucrose, dextrose hydrate, and glycerol have been recorded. Rotational correlation times of the radicals have been established through computer simulations of the experimental spectra. It is found that Flavin radicals undergo strongly anisotropic motions in solution. Analysis of the dependences of the rotational correlation time and the residual linewidths of the flavin spectra indicate that all three flavins form molecular aggregates with the solutes in order of increasing strength: glycerol < sucrose < dextrose. The nature of the flaving solute interaction is dependent upon the solute rather than the Flavin. The electron paramagnetic resonance spectra of 8-hydroxyriboflavin, 8-formylriboflacin, and 8-carboxyroboflavin anion radical are presented. It is proposed that the observed linewidth effects are due to a mechanism such as exchange narrowing.
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    The extraction of mineral acids and transition metal ions by Di(n-octyl) arsinic acid (DOAA) in chloroform
    (1972) Olivares, Alberto Manuel; Irgolic, Kent J.; Halliwell, Robert S.; Koenig, Karl J.; Whealy, Roger D.; Zingaro, Ralph A.
    The extraction of HClO₄, HCl, HBr, HNO₃, H₂SO₄, HI and the metal ions SC(III) in HCl solution, Ce(III), Eu(III), Ho(III) and Yb(III) in acetate buffered solutions by chloroform solutions of diocytlarsinic acid (DOAA), (n-C₈H₁₇)₂AsOOH, was investigated. The loading experiments with perchloric acid showed that 0.1 M DOAA, after equilibration with HClO₄ of initial concentration of 5 M to 9 M, forms a 1:1 adduct DOAA[dot]HClO₄. Molecular formula determinations indicate that this adduct is dimeric. Except for sulfuric and hydriodic acids, the loading curves for the other mineral acids are similar to the curve for HClO₄ with well defined plateaus at molar ratios of [H⁺][subscript o]/[DOAA][subscript o] equal to unity in the range of initial aqueous acid concentrations from about 3 M to 7 M. Reagent dependence studies showed that the mineral acids form 2:1 adducts with DOAA at 0.1 M aqueous concentrations. Sulfuric acid was not extracted at this concentration. A mixture of 2:1 and 2:2 adducts is formed between 0.5 M and 1.0 M aqueous sulfuric acid. Hydriodic acid reduced DOAA. Water was coextracted with all mineral acids. The concentration of water in the organic phase decreased with increasing aqueous acid concentrations above 6 M. ...
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    The extraction of niobium (V), tantalum (V), mercury (II), silver (I), cobalt (II), iron (III) and cadmium (II) by di(n-octyl) arsinic acid (HDOAA) in chloroform
    (1975) Dominguez, Richard Joseph Gilbert; Irgolic, Kurt J.; Fendler, Janos H.; Meyer, Edgar; Zingaro, Ralph A.
    The extraction of Nb(V) and Ta(V) from HCl, H₂SO₄ and H₂C₂O₄ solutions, Hg(II) from HCl solutions, Ag(I) from HNO₃ solutions, Co (II) from HCl solutions, Fe(III) from HCl, HNO₃, H₂SO₄, and HCIO₄ solutions and Cd(II) from HCl solutions by 0.1 M solutions of dioctylarsinic acid, (n-C₈H�₇)₂AsOOH (HDOAA) in chloroform was investigated. The extraction of these metal ions was studied as a function of the equilibrium aqueous phase pH and the reagent concentration using radionuclides as tracers. In the niobium and tantalum extraction experiments the oxalates MO(OH)C₂O₄(M=Nb,Ta) were employed. Both of the elements were efficiently extracted from strongly acidic aqueous solutions with maximum E°[subscript a] values of 93 (from 6 M HCl) and 125 (from 1 M H₂SO₄) for the niobium system and 250 (from 6 M HCl) and 386 (from 4 M H₂SO₄) for the tantalum system. The pH and reagent dependence studies suggested that a monobasic trinuclear niobium species is extracted as an ion pair with 10 HDOAA molecules associated with the trimer. Tentatively, the formula (H₂DOAA)�[Nb₃-(HDOAA)g (C₂O₄,OH,O,H₂O)[subscript n]]� is proposed. The composition of the extracted tantalum complex was found to be dependent on the shaking time. After shaking for one hour the data suggested the formula (H₂DOAA)�[Ta(HDOAA)₂(C₂O₄,O,OH)[subscript n]]� for the extracted species whereas after 36 hours shaking the tantalum to HDOAA ratio decreased from 2:1 to 1:1. ...
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    Identification and determination of arsenic compounds by chromatographic and mass spectrometric methods
    (1983) Ehrhardt, Kenneth Charle; Irgolic, K. J.; Rowe, M. W.; Tieh, T. T.; Zingaro, Ralph A.
    Arsenate, arsenite, methylarsonic acid and dimethylarsinic acid are arsenic compounds commonly found in the environment. An efficient method combining high performance liquid chromatography with a Hitachi-Zeeman graphite furnace atomic absorption spectrophotometer was developed for the separation and quantitative determination of these four arsenic compounds. The compounds were separated by ion-pair chromatography (C-18 reverse phase column, 75% H(,2)O/25% CH(,3)OH saturated with tetraheptylammonium nitrate as the mobile phase, pure methanol for the elution of arsenate). The samples to be injected for chromatography may contain 30 to 300 ng As of each compound. The separation scheme developed for the four arsenic compounds were used to speciate these compounds in drinking waters. The mass spectral behavior or the organylarsonic acids, RAsO(,3)H(,2) (R = CH(,3), C(,2)H(,5), C(,3)H(,7), C(,9)H(,19), and C(,6)H(,5)), the diorganylarsinic acids, R(,2)AsOOH (R = CH(,3), C(,2)H(,5), C(,3)H(,7), C(,4)H(,9), C(,5)H(,11), C(,8)H(,17), c-C(,6)H(,11), C(,6)H(,5), and C(,6)H(,5)CH(,2)CH(,2)), the organyldiiodoarsines, RAsI(,2) (R = CH(,3), C(,2)H(,5), C(,3)H(,7), C(,4)H(,9), C(,5)H(,11), C(,7)H(,15), C(,9)H(,19), C(,15)H(,31), C(,17)H(,35), C(,19)H(,39), C(,6)H(,5), and C(,6)H(,5)CH(,2)CH(,2)), and the diorganyliodoarsines, R(,2)AsI (R = CH(,3), C(,8)H(,17), C(,9)H(,19), C(,11)H(,23), C(,13)H(,27), C(,14)H(,29), C(,15)H(,31), C(,17)H(,35), C(,19)H(,39), c-C(,6)H(,11), and C(,6)H(,5)CH(,2)CH(,2)) were investigated to explore the usefulness of mass spectrometry as a tool for the identification of organic arsenic compounds. The organylarsenic acids were thermally dehydrated and decomposed at the probe temperatures required to obtain satisfactory spectra. The complicated spectra of the decomposition products are not very useful for analytical purposes. The reactions of organylarsenic acids with aqueous hydriodic acid produced organyliodoarsines which are more volatile than their parent acids. The mass spectra of the iodoarsines contain predominant molecular ion peaks, which can be used for the identification of long- and short-chain compounds.
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    The influence of chelation on absorption and translocation of iron, copper, manganese, and zinc by the cotton plant
    (1971) Guinn, Gene; Martell, Arthur E.; Couch, J. R.; Crookshank, H. R.; Zingaro, Ralph A.
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    Investigation of high temperature gaseous species by Knudsen cell mass spectrometry and matrix isolation infrared spectroscopy
    (1972) Cocke, David Leath; Gingerich, Karl A.; Becka, Richard; Coon, Jesse B.; Zingaro, Ralph A.
    The equilibria involving gaseous species over the condensed Ho-Ag system (series I), the condensed Ho-Al-Au system (series II), the condensed Ce-Pd-C system (series III), and the condensed TiP-Rh-C system (series IV) have been investigated by the high temperature mass spectrometric technique. The third law enthalpies and, where possible, the second law enthalpies have been determined for the following reactions: Ho(g) + Agâ‚‚(g) = HoAg(g) + Ag(g), HoAg(g) + Ho(g) = Hoâ‚‚(g) + Ag(g), Hoâ‚‚(g) = 2Ho(g), Ho(l) + Ho(g) = Hoâ‚‚(g), for series I; HoAu(g) + Al(g) = Ho(g) + AlAu(g), for series II; CePd(g) = Ce(g) +Pd(g), CePd(g) + Câ‚‚(g) = CeCâ‚‚(g) + Pd(g), Ce(g) + 2C(graph) = CeCâ‚‚(g), for series III; Rh(g) + C(graph) = RhC(g), Ti(g) + 2C(graph) = TiCâ‚‚(g), Rh + 2C(graph) = RhCâ‚‚(g), RhCâ‚‚(g) + Rh(g) = 2RhC(g), TiCâ‚‚(g) + Rh(g) = RhCâ‚‚(g) + Ti(g), RhC(g) = Rh(g) + C(g), RhC(g) + Ti(g) = TiRh(g) + C(g), TiCâ‚‚(g) + Rh(g) = TiRh(g) + Câ‚‚(g), Rhâ‚‚(g) + C(g) = RhC(g) + Rh(g), TiRh(g) = Rh(g) + Ti(g), Rhâ‚‚(g) = 2Rh(g), for series IV. ...
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    Investigation of the intermediate steps in the curtius synthesis of amino phosphonic acids
    (1966) Lee, Charles Wah; Isbell, A. F.; Conway, D. C.; Rose, Norman C.; Prescott, J. M.; Zingaro, Ralph A.
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    Luminescence probe studies of ion-containing polymers
    (1984) Prieto, Nelson Eduard; Martin, Charles R.; Amoss, Max S.; Rowe, Marvin W.; Zingaro, Ralph A.
    Luminescence probe studies were used to obtain information about the morphology and chemical properties of ion-containing polymers (ionomers). Studies were conducted in polyelectrolyte solutions and solid state ionomer membranes. The data obtained was compared to similar data from homogeneous solvents and micellar solutions. The response of the luminescence probes were similar in the ionomer membranes and their corresponding solutions. A concerted hydrophobic/electrostatic interaction was implied in the binding of the probe ions to the polyanions in solution. This concerted binding provided an effect which could undoubtedly be exploited in a luminescence titration method. The basis for the determination of the equivalent weight or the concentration of a poly-electrolyte solution using this method was explored. Further evidence for the importance of hydrophobic interactions in ionomeric systems is presented. The effects of ionic sites clustering in ionomer membranes were studied. The results suggested the ionic clusters have frequent local instrusions of the chain material phase and are dynamic with respect to water content and counterion. A relatively small fraction of the ionic sites were found to be incorporated in a very hydrophobic domain. The particular operative interactions between the probes and the ionomers were found to be dependent on the nature of the polymer chain material. The significance of these results is discussed.
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    Mass spectrometric characterization of water soluble organics in heavy oil retort
    (1994) Lewis, Tanya Maranda; Russell, David H.; Brown, Kirk W.; Schweikert, Emile A.; Zingaro, Ralph A.
    A unified scheme is developed to demonstrate the necessity of a synergistic approach using several mass spectrometry methods for characterization and identification of water soluble organics in heavy oil retort. Elements of the scheme include a method for gas chromatography-mass spectrometry (GC-MS), high resolution mass spectrometry (HRMS) and mass spectrometry-mass spectrometry (MS-MS) with electron impact and fast atom bombardment ionization and a computerized library search. GC-MS, HRMS and MS-MS are well-established as powerful and versatile tools for identifying components of organic mixtures. Many improvements have been incorporated in order to provide the maximum amount of information that can be derived from the mass spectrometry methodologies. Each element of the analytical scheme is applied to complex samples of aqueous organic materials extracted from heavy oil retorts. The project focuses on development of methods rather than acquisition of compositional data; therefore, emphasis is placed on data which most clearly illustrate the utility and limitations of a given method. Criteria is developed to evaluate the informational content of the mass spectrometric methods. The elements of the scheme provide different perspectives on components in a highly complex sample. Each methodology supplies specific data not obtainable from other methods. GC-MS serves as an excellent survey analysis, and when combined with selective ion monitoring and the library search program, isolates specific groups of compounds without extensive sample treatment. MS-MS and the library search program are used to extract structural information. HRMS is used to determine elemental composition of mass resolved ions. PBM assists in structure elucidation by providing state-of-the-art library retrieval capabilities. PBM compensates both for the presence of mixtures in an unknown and for the wide variety of experimental conditions under which the reference library compounds were run. The inherent analytical power of the individual methodologies is extensive; however, results indicate that the mass spectrometry methods are used most effectively in concert with each other.
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    Metal-centered and ligand-centered autoxidations involving u-peroxo-bridged cobalt dioxygen complexes
    (1984) Raleigh, Carl Jame; Martell, A. E.; Darensbourg, D.; Wild, J. R.; Zingaro, Ralph A.
    The autoxidation of cobaltous complexes containing tetaethylenepentramine (TETREN), 1,9-bis(4-imidazolyl)-2,5,8-triazanonane (IMDIEN), 2,6-bis(2-(3,6-diazahexyl)) pyridine (EPYDEN), 1,9-bis(2-pyridyl)-2,5,8-triazanonane (PYDIEN), and 1,11-bis(2-pyridyl)-2,6,10-triazaundecane (PYDPT) react through (mu)-peroxo-bridged cobalt(III) dioxygen complexes, resulting in ligand oxidative dehydrogenation or a simple metal-centered oxidation. These reactions are shown to be first order with respect to the concentration of both the (mu)-peroxo-bridged cobalt(III) dioxygen complex and the hydroxide concentration. Reaction products are identified for the simple cobalt(II) oxidation containing TETREN, IMDIEN and EPYDEN as the cobalt(III) chelates and hydrogen peroxide; and for the coordinated ligands PYDIEN and PYDPT, the oxidative dehydrogenation products are imines conjugated to the pyridine ring, water, and cobalt(II). The cobalt(II) complex of the ligand that has undergone oxidative dehydrogenation reoxygenates and further oxidative dehydrogenation of the ligand then takes place. It is proposed that the mechanistic differences in the autoxidation reactions are dependent on the conformation of the aromatic and aliphatic amino groups in the coordination sphere of the (mu)-peroxo-bridged cobalt(III) dioxygen complexes having pyridyl-containing pentadentate polyamines as ligands.
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    An NMR investigation of the metal ion and proton catalyzed reactions of some vitamin B-6 Schiff base systems
    (1969) Abbott, Edwin Hunt; Martell, Arthur E.; Eubank, P. T.; Lunsford, Jack H.; Zingaro, Ralph A.
    The alpha and beta deuteration of the alpha amino acids valine and alpha aminobutyric acid is easily accomplished by heating D₂O solutions which are 1 M in the amino acid, 0.2 M in pyridoxal, and 0.1 M in aluminum(III) ion. The effects of the deuterium which is introduced make possible the direct inference of the sites being deuterated not only by changing the spin-spin coupling but also by introducing a slight shielding of protons vicinal to the substituted site. The extension of this technique to other amino acids and to peptides is discussed, and a mechanism which involves transamination of the aluminum(III) complexes of the aldimine Schiff base, to the ketimine complex, exchange of the beta protons of the ketimine, and transamination back to the aldimine form is presented. At pD 9, the alpha proton exchange is much more rapid than the beta exchange. This is attributed to the predominance of the pyridoxal, aluminum(III) catalyzed racemization reaction over transamination in this range. ...
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    Normal coordinate analyses of trimethylarsine sulfide and trimethylarsine selenide
    (1972) Kolar, Frank Lee; Zingaro, Ralph A.; Hedges, R. M.; Hossner, L. R.; Irgolic, Kurt; Meyers, Edward A.; Moore, Bill C.
    Trimethylarsine sulfide and trimethylarsine selenide and their perdeuterated analogues were synthesized for the purpose of carrying out vibrational analyses. The mid-infrared (4000 - 200 cm⁻¹) and far-infrared (400 - 30 cm⁻¹) spectra of the solid compounds as well as the Raman spectra of saturated aqueous solutions were measured for each compound. The Raman spectra of the solid trimethylarsine sulfides-d₀ and -d₉ are reported. The 33 fundamental vibrational frequencies (omitting the methyl torsions) are assigned. The assignments are made on the basis of symmetry selection rules and comparison with structurally related molecules such as trimethylarsine oxide and trialkylphosphine chalcogenides. Detailed normal coordinate calculations were carried out to reinforce these assignments. A valence force field and C[subscript 3v] symmetry were assumed for each molecule. A set of 24 significant force constants were refined to give a least squares fit of the calculated frequencies to the observed frequencies. The values of the force constants for trimethylarsine sulfide and trimethylarsine selenide were found to be essentially the same except for the As-S and As-Se bond stretches, the CAsS and CAsSe angle bends, and the interaction constants involving any of these bond stretches or angle bends. Calculations of the potential energy distributions for each molecule show that there exists little coupling between the different symmetry coordinates for each of the compounds.