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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Untersuchungen über Formamid als Lösungsmittel für anorganische Salze und über die Elektrolyse der Lösungen

Röhler, Hermann, January 1909 (has links)
Thesis (doctoral)--Universität Leipzig, 1909. / Vita. Includes bibliographical references (p. 67).
2

Solvated electron yield in the radiolysis of formamide

Head, David Alan January 1969 (has links)
Some of the thermal electrons formed when a liquid is subjected to high-energy radiations eventually become solvated. These solvated electrons (e⁻solv) are of special chemical interest due to their powerful reducing nature. The mechanism by which solvation occurs is not well understood, but must depend upon several solvent properties, of which the static dielectric constant is probably the most important. Some insight into the factors determining electron solvation may be gained through a knowledge of the radiation yields of e⁻solv in a wide variety of liquids. Since water is the liquid of highest dielectric constant (є=80) studied to date it seemed worthwhile to extend our knowledge beyond this point. Of the four common liquids with dielectric constants greater than that of water, formamide (є=109) was best suited for this study. In the present work the e⁻solv yield in formamide was found to be only slightly greater than its yield in water, which is surprising considering the large increase in dielectric constant. A modified correlation which, in addition to the dielectric constant, included the solvating ability and the stopping power of the solvent was shown to give a better fit to data for a number of liquids (resolving, for instance, the ammonia anomaly), indicating that these factors also govern the yield of e⁻solv. The yields of hydrogen, carbon monoxide, and nitrogen formed when formamide and its nitrous oxide solutions were irradiated with ⁶⁰Co Ƴ-rays gave information concerning the e⁻solv yield. Using the electron scavenger N₂O and the scavenger pairs N₂O/Cd⁺⁺, N₂O/Ag⁺, and N₂O/acid, the number of e⁻solv formed per 100 eV of energy absorbed was found to be 2.9±0.1. This yield corresponds fairly closely with the value which can be calculated using Freeman's non-homogeneous model. The primary yields of H₂ HCONH*₂, CO, and HCO were evaluated as .75±0.05, 0.4±0.1, ≤ 0.55±0.07, and ≥ 1.15±0.20 molecules/l00eV respectively. At low doses (up to ∼5xl0¹⁹ eV/ml) the yields of H₂, N₂, and CO were dose independent for the dose rate of ∼4xl0¹⁷ eV/ml-minute used. In two types of pulse radiolysis experiments light absorption was not observed in the 4500 Å to 8500 Å wavelength region contrary to expectations. A comparison of these results with those from other work may be interpreted as suggesting that the half-life of formation of e⁻solv, in formamide is between 0.36 and 1.9 microseconds. This tentative conclusion, if correct, would mean that e⁻solv was a secondary, not a primary, product in formamide and this would be of general significance to the primary processes of radiation chemistry. / Science, Faculty of / Chemistry, Department of / Graduate
3

The effect of dissolved substances on the velocity of crystallization of formamide The effect of dissolved substances on the velocity of crystallization of water ; On the preparation of formamide /

Brann, Albert. January 1918 (has links)
Presented as thesis (Ph. D.)--University of Wisconsin--Madison, 1918. / Reprinted from Journal of the American Chemical Society. Part 1: vol. XL, no. 8 (Aug. 1918), p. [1184]-1187. Part 2: vol. XL, no. 8 (Aug. 1918), p. [1168]-1184. Part 3: vol. XL, no. 5 (May 1918), p. [793]-796. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
4

Part I. [alpha]-hydrogen exchange of methoxyacetone, ethyl isopropyl ketone, and cyclopentanone ; Part II. Hydrolysis of formamide /

Sinha, Ashoke January 1983 (has links)
No description available.
5

Bubbles, Thin Films and Ion Specificity

Henry, Christine L., christine.henry@alumni.anu.edu.au January 2009 (has links)
Bubbles in water are stabilised against coalescence by the addition of salt. The white froth in seawater but not in freshwater is an example of salt-stabilised bubbles. A range of experiments have been carried out to investigate this simple phenomenon, which is not yet understood.¶ The process of thin film drainage between two colliding bubbles relates to surface science fields including hydrodynamic flow, surface forces, and interfacial rheology. Bubble coalescence inhibition also stands alongside the better known Hofmeister series as an intriguing example of ion specificity: While some electrolytes inhibit coalescence at around 0.1M, others show no effect. The coalescence inhibition of any single electrolyte depends on the combination of cation and anion present, rather than on any single ion.¶ The surfactant-free inhibition of bubble coalescence has been studied in several systems for the first time, including aqueous mixed electrolyte solutions; solutions of biologically relevant non-electrolytes urea and sugars; and electrolyte solutions in nonaqueous solvents methanol, formamide, propylene carbonate and dimethylsulfoxide. Complementary experimental approaches include studies of terminal rise velocities of single bubbles showing that the gas-solution interface is mobile; and measurement of thin film drainage in inhibiting and non-inhibiting electrolyte solution, using the microinterferometric thin film balance technique.¶ The consolidation of these experimental approaches shows that inhibiting electrolytes act on the non-equilibrium dynamic processes of thin film drainage and rupture between bubble surfaces – and not via a change in surface forces, or by ion effects on solvent structure. In addition, inhibition is driven by osmotic effects related to solute concentration gradients, and ion charge is not important.¶ A new model is presented for electrolyte inhibition of bubble coalescence via changes to surface rheology. It is suggested that thin film stabilisation over a lifetime of seconds, is caused by damping of transient deformations of film surfaces on a sub-millisecond timescale. This reduction in surface deformability retards film drainage and delays film rupture. It is proposed that inhibiting electrolyte solutions show a dilational surface viscosity, which in turn is driven by interfacial concentration gradients. Inhibiting electrolytes have two ions that accumulate at the surface or two ions that are surface excluded, while non-inhibiting electrolytes have more evenly distributed interfacial solute. Bubble coalescence is for the first time linked through this ion surface partitioning, to the ion specificity observed at biological interfaces and the wider realm of Hofmeister effects.¶
6

The purine world: experimental investigations into the prebiotic synthesis of purine nucleobases and intercalation of homopurine DNA duplexes

Buckley, Ragan 13 June 2012 (has links)
Formamide is a solvent of great interest to prebiotic chemists because it is liquid over a wide range, it is less volatile than either water or HCN, and it possesses a versatile reactivity. When formamide is heated in the presence of minerals or inorganic catalysts, a variety of products including purine nucleobases are generated. Irradiation of formamide reaction solutions with ultraviolet light increases the yield and diversity of products, and eliminates the need for a mineral catalyst. We have also performed formamide reactions in the presence of pyrite, a mineral which is likely to have been available on the primordial Earth, under a variety of atmospheric conditions. Our results indicate the greatest yield and diversity of products result from the combination of a pyrite mineral catalyst, heat, UV irradiation, and a carbon dioxide atmosphere. Purine nucleobases are simple to synthesize in model reactions and they stack well in aqueous solution; it has been hypothesized that the first nucleic acids were composed of only purine bases, and that water-soluble, cationic, aromatic molecules with large stacking surfaces (“”molecular midwives””) may have aided the assembly of the earliest nucleic acid analogs. We have characterized the interactions of various intercalators with a standard DNA duplex as well as with an antiparallel homopurine DNA duplex and have determined that molecules which possess four or more rings and a curved shape interact selectively with all-purine DNA; such molecules can serve as models for putative prebiotic midwives.
7

Degenerate Oligonucleotide Primed - Polymerase Chain Reaction Evaluation And Optimization To Improve Downstream Forensic STR Analysis Of Low Quality/Low Quantity DNA

Thompson, Lindsay Paige 01 January 2006 (has links)
When forensic biological samples yield low quality/low quantity DNA, thecurrent STR analysis methods do not generate acceptable profiles. Whole genomeamplification can be used to pre-amplify the entire genome for downstream analyses. A commercially available kit for DOP-PCR, a form of WGA, is currently being used in the clinical for downstream single locus targets. Forensic analyses utilize a multiplex amplification. This study determined that the "home brew" created by our lab performs the same as the commercially available kit. Future optimization studies of DOP-PCR can utilize this "home brew". Additionally, this research determined that a 10 second increase in electrokinetic injection time onto the Capillary Electrophoresis (CE) in combination with a post-STR amplification purification and elution into formamide produces a slightly higher percent STR allele success over the standard protocol. After future optimization studies, this may be a useful method to obtain more accurate and complete STR profiles from low quality/low quantity biological samples.
8

Estudo do Comportamento Eletroquímico do Európio em Formamida pelo Método de Cronopotenciometria / Study the electrochemical behavior of europium in formamide by the method of chronopotenciometry

Raboczkay, Tibor 15 March 1972 (has links)
No presente trabalho é estudada a reação Eu3+ + e = Eu2+ (I) com auxílio do método cronopotenciométrico em soluções aquosas, e em misturas de formamida e água, empregando como eletrodo de trabalho o eletrodo de reservatório de mercúrio e como eletrodo de referência o eletrodo de colamelano saturado (em soluções de NaClO4 1 M, à temperatura de 25,0 ± 0,1 °C). Foi estudada a influência dos seguintes fatores: (1) concentração da espécie eletroativa; (2) densidade da corrente; (3) porcentagem de formamida e (4) pH de solução. O processo representado por (I) apresenta um comportamento quase-reversível em misturas de formamida e água de 0 a 50 % em volume. A determinação dos parâmetros cinéticos (ks, α) mostra que a reação é alterada não só pelo aumento da porcentagem de formamida, mas também pelo pH da solução. O pH altera pronunciadamente o potencial de meia-onda anódico; as variações dos potenciais de meia-onda catódicos são relativamente, pequenas. Com o abaixamento do pH da solução aumenta-se o caráter irreversível do processo. A reação (I) em misturas de formamida e água contendo 70 - 100 % de formamida em volume é reversível. Nestas condições o pH não altera a cinética da reação. Os dados experimentais foram interpretados em termos de (1) alteração da natureza da espécie eletroativa com o aumento da concentração da formamida e a variação do pH e/ou (2) eventuais alterações da estrutura da dupla camada elétrica com a variação do pH e da concentração de formamida. Foram determinados também os coeficientes de difusão do Eu (III) nas diferentes porcentagens de formamida. / In this work the reaction Eu3+ e Eu2+ (I) was studied by the chronopotentiometric method in aqueous solutions and in mixtures of formamide and water, using the mercury pool electrode as working electrode and the S.C.E. as reference electrode (in l M NaClO4, at 25,0 ± 0,1 °C). The influence of the following factors was studied: (1) concentration of the electroactive species, (2) current density, (3) percentage of formamide and (4) pH of the solution. The electrode process (I) in mixtures of formamide and water 0 - 50 % v/v, was found to be quasi-reversible. The kinetics of the reaction (ks, α) were also altered by the pH, which strongly affected the position of the anodic half-wave potential, while the cathodic one was only slightly altered. As the pH of the solution decreased the electrode process approached irreversible behaviour. Reaction (I) in mixtures of formamide and water 70 - 100 % v/v, was found to be reversible. Under these conditions the pH was found not to affect the kinetics of the reaction. The experimental data were interpreted on the basis of (1) change in the nature of the complex species as the concentration of formamide increases or as pH is altered and/or (2) changes of the structure of the electrical double layer with changing concentration of the formamide and with variations in the pH. It was also possible to determine the diffusion coefficients of Eu(III) at different percentages of formamide.
9

Estudo do Comportamento Eletroquímico do Európio em Formamida pelo Método de Cronopotenciometria / Study the electrochemical behavior of europium in formamide by the method of chronopotenciometry

Tibor Raboczkay 15 March 1972 (has links)
No presente trabalho é estudada a reação Eu3+ + e = Eu2+ (I) com auxílio do método cronopotenciométrico em soluções aquosas, e em misturas de formamida e água, empregando como eletrodo de trabalho o eletrodo de reservatório de mercúrio e como eletrodo de referência o eletrodo de colamelano saturado (em soluções de NaClO4 1 M, à temperatura de 25,0 ± 0,1 °C). Foi estudada a influência dos seguintes fatores: (1) concentração da espécie eletroativa; (2) densidade da corrente; (3) porcentagem de formamida e (4) pH de solução. O processo representado por (I) apresenta um comportamento quase-reversível em misturas de formamida e água de 0 a 50 % em volume. A determinação dos parâmetros cinéticos (ks, α) mostra que a reação é alterada não só pelo aumento da porcentagem de formamida, mas também pelo pH da solução. O pH altera pronunciadamente o potencial de meia-onda anódico; as variações dos potenciais de meia-onda catódicos são relativamente, pequenas. Com o abaixamento do pH da solução aumenta-se o caráter irreversível do processo. A reação (I) em misturas de formamida e água contendo 70 - 100 % de formamida em volume é reversível. Nestas condições o pH não altera a cinética da reação. Os dados experimentais foram interpretados em termos de (1) alteração da natureza da espécie eletroativa com o aumento da concentração da formamida e a variação do pH e/ou (2) eventuais alterações da estrutura da dupla camada elétrica com a variação do pH e da concentração de formamida. Foram determinados também os coeficientes de difusão do Eu (III) nas diferentes porcentagens de formamida. / In this work the reaction Eu3+ e Eu2+ (I) was studied by the chronopotentiometric method in aqueous solutions and in mixtures of formamide and water, using the mercury pool electrode as working electrode and the S.C.E. as reference electrode (in l M NaClO4, at 25,0 ± 0,1 °C). The influence of the following factors was studied: (1) concentration of the electroactive species, (2) current density, (3) percentage of formamide and (4) pH of the solution. The electrode process (I) in mixtures of formamide and water 0 - 50 % v/v, was found to be quasi-reversible. The kinetics of the reaction (ks, α) were also altered by the pH, which strongly affected the position of the anodic half-wave potential, while the cathodic one was only slightly altered. As the pH of the solution decreased the electrode process approached irreversible behaviour. Reaction (I) in mixtures of formamide and water 70 - 100 % v/v, was found to be reversible. Under these conditions the pH was found not to affect the kinetics of the reaction. The experimental data were interpreted on the basis of (1) change in the nature of the complex species as the concentration of formamide increases or as pH is altered and/or (2) changes of the structure of the electrical double layer with changing concentration of the formamide and with variations in the pH. It was also possible to determine the diffusion coefficients of Eu(III) at different percentages of formamide.
10

Syntheses, X-ray Diffraction Structures, and Kinetics on New Formamidinate-Substituted Triosmium Clusters

Yang, Li 12 1900 (has links)
The reaction between the formamidine ligand PriN=CHNHPri and the activated cluster Os3(CO)10(MeCN)2 has been studied. A rapid reaction is observed at room temperature, yielding the hydride clusters HOs3(CO)9[μ-OCNPriC(H)NPri] and HOs3(CO)10[μ-NPriC(H)NPri] as the principal products. The spectroscopic data and X-ray diffraction structures of those formamidinate-substituted clusters will be present. The thermal reactivity of the clusters has been investigated, with the face-capped cluster HOs3(CO)9[μ-NPriC(H)NPri] found as the sole observable product. The relationship between these three clusters has been established by kinetic studies, the results of which will be discussed.

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