In this thesis reactions of urea and its N-alkyl derivatives with monoketones, α-diketone s, enzladehyde, acyloins, diaminoethane and its N-alkyl derivatives, oxidation of alkyl and aryl derivatives of thiourea, nitration of Hector's Base, effect of bases on the adduct of Hector's Base, structural elucidation of Hector's Base, Dost's Base and related compound by the application of spectral techniques, and the reaction of picric acid with creatinine in alkaline media are discussed. Reactions of monoketones (acetone, mesityl oxide, aceto-phenone and benzophenone) and benzaldehyde with urea, 1-methylurea and 1,3-dimethylurea gave white crystalline product These products were identified by proton and carbon-13 nmr techniques, physical, chemical and spectrophotometric methods wherever appropriate. A mechanism for these reactions has been proposed. In all these cases, monoketones (except benzophenone) undergo self-condensation in acid solution and the resulting products react with ureas. In the absence of ureas there is further self-condensation to yield hydrocarbons. In case of benzaldehyde reaction, it is the urea which undergoes self-condensation and resulting biuret, in turn, reacts with benzaldehyde. Moreover, it has been found that at least one methyl group adjacent to carbonyl group is involved in the self-condensation process. If methyl groups on either side of carbonyl group are replaced by phenyl groups (benzophenone) then there is no reaction.

Chi-Keung Lam. / "August 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 202-210). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

In the present study, a new "anti-Bredt" bicyclic urea, 1,3-diazabicyclo[3·3·1]nonan-2-one, and an isomeric bond-bridged reference compound 1,8-diazabicyclo[4·3·0]nonan-9-one, were synthesized. The [3·3·1] urea was prepared in two ways. 3-Aminomethylpiperidine was reacted with phosgene. Deprotonation of the precipitated ammonium salt with triethylamine gave the urea. In another method, thermal depolymerization (in vacuo) of a glassy product arising from the reaction of 3-aminomethylpiperidine with diphenyl carbonate afforded the urea. The [4·3·0] urea was obtained through the reaction of diphenyl carbonate with 2-aminomethylpiperidine. No glassy intermediate was observed. The [4·3·0] and [3·3·1] ureas resisted hydrolysis. The former would not polymerize either in bulk or in solution at any temperature with or without initiator catalysts. At 120° and above the [3·3·1] urea bulk polymerized within 30 minutes with or without catalysts. The uncatalysed thermal polymerization gave lower molecular weight polymers in lower yield than the catalysed one. Cationic initiator, phenylphosphonic acid, and anionic potassium tertiary butoxide catalysts gave highest molecular weight polymers. Comparatively, the anionic initiator generated a higher molecular weight polymer than the cationic one. Dibutyltin oxide which is a coordination metal catalyst was also effective in generating high polymer but the yield compared favorably only with the uncatalysed thermal polymerization. The bulk polymerization of the [3·3·1] urea is one of the rare cases of polymerization of a bicyclo [3·3·1] nonan derivative. The mechanism proposed for the thermal polymerization of [3·3·1] urea involved the dissociation of the urea to an aminoisocyanate which then propagated the polymerization. The reaction of 3-aminopiperidine with diphenyl carbonate afforded a urea which was proposed to be a dimer of the desired urea, 1,6-diazabicyclo[3·2·1]octan-7-one. The unsuccessful syntheses of two ureas possessing two nitrogen bridgehead atoms, 1,5-diazabicyclo[3·2·1]octan-8-one, and 1,5-diazabicyclo[3·3·1]nonan-9-one, and another which was seven-membered, 1,3-diazabicyclo[3·2·2]nonan-2-one, were explained in terms of their canonical forms violating Wiseman's rule. However, a nuclear magnetic resonance (NMR) spectrum evidence of the formation of 1,5-diazabicyclo[3·2·1]octan-8-one in the NMR tube was presented.

Durch die Insertion von CO2 in die Si-N-Bindung von Diaminosilanen sind Di(carbamoyloxy)silane zugänglich. Mittels thermischer Zersetzung dieser Insertionsprodukte können Siloxane und entsprechende Harnstoffderivate erhalten werden. In dieser Arbeit wurden die chemischen Reste in diesen Systemen variiert um Siloxane mit verschiedenen Substitutionsmustern zu erhalten. Außerdem wurde das Substituentenaustauschverhalten des System Aminosilan/Carbamoyloxysilan näher untersucht. Dabei konnte die Substanzklasse der Amino(carbamoyloxy)silane nachgewiesen werden. Auch die Adaption der Versuche auf Triaminosilane und Aminodisilane wurde erfolgreich durchgeführt. Dadurch wurden vernetzte Siloxane als Thermolyseprodukte erhalten. Einige Carbamoyloxydisilane bilden zudem fünffach koordiniertes Silicium aus.:Vorwort 1. Einleitung und Motivation 2. Literaturteil (Siloxane/Silikone und Harnstoffe) 3. Diaminosilane 4. CO2-Insertion in Diaminosilane - Synthese von Di(carbamoyloxy)silanen 5. Thermolyse 6. Triaminosilane und Tri(carbamoyloxy)silane 7. Aminodisilane und Carbamoyloxydisilane 8. Zusammenfassung und Ausblick 9. Experimenteller Teil 10. Anhang

Lisozima mostrou-se capaz, quando dispersa em certos meios orgânico-aquosos, de gerar sistemas pseudoplásticos que evoluem espontaneamente para redes de caráter viscoelástico. Esse fenômeno foi investigado neste estudo, para lisozima dispersa em uma série de misturas binárias contendo derivados de uréia como componente orgânico. Devido aos notáveis efeitos observados para um de tais derivados, a saber, tetrametiluréia (TMU), especial atenção foi dedicada aos sistemas contendo esse composto. O enfoque experimental incluiu espectroscopia Raman, microcalorimetria, reologia e espalhamento de raios X a baixo ângulo (SAXS). O trabalho envolveu o estudo dos sistemas orgânico-aquosos isolados e na presença de proteína. No primeiro caso, foi feita uma investigação espectroscópica e microcalorimétrica dos sistemas quanto a aspectos relativos à segregação de microdomínios na fase liquida e sua conseqüente relação com a deflagração da transição viscoelástica na proteína. Foram observadas descontinuidades nos valores de entalpias de excesso de mistura para o sistema TMU/água em torno de wTMU = 0,6, assim como padrões peculiares de comportamento espectral em torno dessa concentração da mistura binária. No segundo caso, os sistemas complexos de proteínas gerados foram investigados sob o ponto de vista morfológico e dinâmico, através das técnicas reológicas e de SAXS. Energias de ativação de fluxo determinadas na região sub-crítica, de comportamento Newtoniano, mostraram uma dependência exponencial direta com wTMU, indicando que mudanças estruturais nos fluidos complexos já ocorrem em regiões de composição do solvente bem abaixo da região de transição em wTMU = 0,6. Na região viscoelástica, 0,6<wTMU<0,9, ensaios de relaxação indicaram a presença de duas populações distintas. A tangente de perda (tg &#948; = G\"/G\') apresentou valores menores que a unidade para todos os casos, indicando o caráter \"solid-like\" das redes nas condições de ensaio. Apesar de seu caráter sólido, as redes mostram-se bastante flexíveis, suportando grandes deformações antes da ruptura, como inferido a partir da larga região viscoelástica linear. A variação nos módulos elástico (G\') e de perda (G\") com a composição do solvente indica a dependência do caráter viscoelástico com a fração de massa de TMU na mistura binária. Na região de baixo conteúdo de água (wTMU = 0,9), um aumento em G\" após a região viscoelástica linear é observado, indicando aumento da estruturação antes da ruptura da rede. As curvas de SAXS foram modeladas em seus fatores de forma e de interferência com uma equação unificada para objetos aleatoriamente distribuídos em um continuum. Os resultados permitiram a construção de um modelo, compatível com as demais evidências experimentais, segundo o qual as moléculas de lisozima encontram-se em duas conformações distintas nas matrizes: uma de conformação estendida e caráter fractal, predominante em wTMU > 0,6, com dimensão máxima de ca. de 160 &#197;, responsável pela interdigitação com espécies fractais vizinhas e uma espécie compacta, minoritária em wTMU > 0,6 (porém predominante em wTMU <0,6), com raio de giro de ca. 48 &#197;, presente nos microdomínios intersticiais aquosos da matriz. Verificou-se ainda a viabilidade de incorporação homogênea de uma metaloproteína, o citocromo-c, às matrizes de lisozima, sem perturbação significativa de sua morfologia, o que constitue um evento de potencial interesse biotecnológico. Os resultados deste trabalho trazem novos suportes experimentais à hipótese de correlação entre inversão na microconfiguração do meio solvente binário e deflagração do processo de transição sol-gel da proteína. / Lysozyme was found to be able, when dispersed in certain organic/aqueous media, to generate pseudoplastic systems that spontaneously evolve to three-dimensional networks with viscoelastic character. This phenomenon was investigated in this study, for lysozyme dispersed in a series of binary mixtures containing urea derivatives as the organic component. Due to the remarkable effects obtained in one of such derivatives, namely, tetramethylurea (TMU), special attention was given to systems containing that compound. The experimental approach included Raman spectroscopy, microcalorimetry, rheology and small angle X ray scattering (SAXS). The work involved the study of the organic/aqueous systems on their own and in the presence of protein. The former consisted of binary liquid mixtures that were spectroscopically and microcalorimetrically investigated as to aspects concerning microdomain segregation in the liquid phase and its consequent relationship with the threshold of the protein viscoelastic transition. Discontinuities in the excess enthalpy of mixture were observed for TMU/water system around wTMU=0.6, as well as peculiar spectral patterns around that same binary mixture concentration. The latter comprised complex protein systems that were investigated both under a morphological and dynamical point of view. Flow activation energies determined in the sub-critical (Newtonian) region showed an exponential increase with wTMU, indicating that structural changes in the comp]ex fluids are under way at solvent concentration regions well below that of the transition, at wTMU = 0.6. In the viscoelastic region, 0.6<wTMU<0.9, relaxation studies indicated the presence of two distinct populations. The loss tangent (tan &#948; = G\"/G\') presented values lower than the unity for all cases, indicating the solid-like character of the matrices, in the assay conditions. Despite their solid character the networks are quite flexible, standing large strains before rupture, as inferred from the large linear viscoelastic region. The variation in elastic (G\') and loss (G\") moduli with solvent composition indicates a dependence of the viscoelastic character on TMU mass fraction in the binary mixture. In the region of low water content (wTMU = 0.9), an increase in G\" after the LVR is observed, indicating increase in network structuring before rupture. SAXS curves were modeled with a unified equation for randomly distributed objects in a continuum. Results allowed the proposal of a model, which is compatible with the experimental evidence obtained through the other techniques in this work, according to which lysozyme molecules occur in two distinct conformations: one expanded and with fractal character, prevailing at wTMU > 0.6, with maximum dimension ca. 160 &#197; and interdigitated with neighbouring fractal species; and a compact conformation, of minor prevalence at wTMU>0.6 (but prevailing at wTMU < 0.6), with radius of gyration ca. 48 &#197;, present in the matrix microdomain interstices. It has also been verified the feasibility of homogeneous incorporation of cytochrome-c into the lysozyme matrices, an event of potential biotechnological interest. Results from this work bring further experimental support to our hypothesis on the correlation between microconfigurational inversion in the binary solvent medium and the sol-gel transition in the protein.