Thesis (doctoral)--München, 1980.

This thesis presents research on the feasibility of applying compliant-ortho-planar springs (COPS) to rotational applications. The primary motivation of this research is the application of COPS to a continuously variable transmission (CVT). The design space limitations, loading conditions, stresses, stress concentrations, and limitations of current design tools, such as pseudo-rigid-body models (PRBM) for COPS, are discussed. A new 3D PRBM is presented along with a discussion on the possible applications of such to a rotating COPS. Stress stiffening and lateral stability are two major phenomena occurring in a rotating COPS. Both phenomena are a direct result of the inertial loads a COPS would be subjected to in a rotational environment. The results show how stress stiffening and lateral buckling in the legs are influenced by design parameters. Conclusions and recommendations for further research are recommended.

<p> An experimental study of vibrational energy transfer in ortho and para NH3(v2) is presented. The vibrational relaxation rates are necessary to characterize mid-IR pulsed and cw NH3 lasers, and the interpretation of these rates is of theoretical importance. Accurate information on the (V-T) process in NH3/N2 mixtures and the (V-V) energy transfer between ortho and para 15NH3 and 14NH3 is now available. </p> <p> First, NH 3 linestrengths and linewidths were accurately measured with a tunable diode laser (TDL) so that ammonia concentrations could be calculated from TDL scans. The energy transfer mechanisms were studied by exciting the v2 vibration of NH3 with a Q-switched cO2 laser and probing the subsequent changes in population with a TDL. A difference in v 2 lifetimes was observed between ortho and para NH3 transitions, and is explained by a (V-V) transfer of energy between the NH3 species. An isolated ortho 15NH3 absorption line was pumped and vibrational transfer of energy was observed to ortho and para 14NH3 and 15NH3. </p> / Thesis / Master of Science (MSc)

No description available.

No description available.

Dans un contexte industriel où les réactions d'oxydation sont réalisées dans des conditions qui ne satisfont pas toujours les principes de la chimie verte, notre groupe étudie des catalyseurs de structure N-hydroxyphtalimide (NHPI), pour l'oxydation aérobie de substrats organiques variés dans des conditions douces. Dans le but d'obtenir des catalyseurs plus actifs, deux familles d'analogues hautement substitués sur le noyau phtalimide ont été préparées, suivant deux nouvelles méthodologies de synthèse. La première consiste en la bis-ortho-métallation / silylation d'acides ortho-phtaliques non protégés, pour un accès très rapide à des analogues silylés du NHPI. Les premiers tests en catalyse d'oxydation aérobie montrent une influence intéressante des groupements silyles sur la stabilité de l'espèce active, via leur encombrement stérique, cela permettant une amélioration de l'activité catalytique. La seconde stratégie inclut une cyclotrimérisation [2+2+2] totalement intramoléculaire d'ène-diyne diesters, pour la construction d'un squelette bis-ortho-lactone pentacyclique innovant. Ces intermédiaires sont aisément transformés en 3,6-bis(2-hydroxyphényl)-4,5-diarylphtalimides, ces composés présentant une symétrie C2 et deux axes d'atropoisomérie. Le dédoublement des énantiomères a été effectué, dans la perspective d'obtenir des catalyseurs d'oxydation aérobie potentiellement énantiosélectifs. / In the chemical industry, oxidation reactions are not often performed in green chemistry conditions. Our group has been studying N-hydroxyphthalimides (NHPI) catalysts for the aerobic oxidation of various organic substrates in mild conditions. In order to obtain more active catalysts, two families of analogs, showing high substitution on the phthalimide core, have been prepared, following two new synthetic methodologies. The first one consists of the bis-ortho-metalation / silylation of unprotected ortho-phthalic acids, for the efficient access to silylated analogs of NHPI. Preliminary tests in aerobic oxidation catalysis show an interesting influence of the bulkiness of the silyl groups towards the active species, because of increases in catalytic activities. The second strategy includes a totally intramolecular [2+2+2] cyclotrimerization of ene-diyne diesters, affording an innovative pentacyclic bis-ortho-lactone scaffold. These intermediates are easily converted to 3,6-bis(2-hydroxyphenyl)-4,5-diarylphthalimides, which present C2 symmetry and two atropoisomeric axis. The resolution of both enantiomers has been performed, in order to access aerobic oxidation catalysts with potent enantioselective activity.

Für die Speicherung und den Transport von Wasserstoff ist die Verflüssigung und anschließende Lagerung in flüssiger Form wegen der deutlich vergrößerten Dichte oft die wirtschaftlichste Lösung. Bei Umgebungstemperatur besteht Wasserstoff zu 75% aus Orthowasserstoff und 25% aus Parawasserstoff. Bei der Verflüssigung ist zu beachten, dass es unterhalb von etwa 250 K zu einer exothermen Umwandlung von Ortho- zu Parawasserstoff kommt. Dadurch wird der Energieaufwand zur Verflüssigung vergrößert. Die Entdeckung, dass es die Allotrope Ortho- und Parawasserstoff gibt, spielte eine wichtige Rolle bei der Entwicklung der Quantenphysik in den zwanziger und dreißiger Jahren des 20. Jahrhunderts. Heute sind vor allem die technischen Aspekte bei der Verflüssigung von Bedeutung. Im wissenschaftlichen Schrifttum fehlte bisher eine zusammenfassende Darstellung der physikalischen und technischen Aspekte. Diese Lücke soll mit dieser Arbeit geschlossen werden. Es werden die Aspekte der Theorie der Unterschiede der beiden Wasserstoffallotrope Orthowasserstoff und Parawasserstoff, die Umwandlung von einem Allotrop in das andere, die Auswirkungen der Unterschiede auf die Stoffgrößen, die mögliche Messung der Anteile, die Selbstumwandlung, die gewollte und ungewollte katalytische Umwandlung sowie die großtechnischen Anwendungen behandelt. Im Rahmen der Arbeit wurde insbesondere die Umwandlung an dem kommerziell erhältlichen Katalysatormaterial Eisenoxid sowie die katalytische Umwandlung an Adsorptionsmaterialien zur kryogenen Wasserstoffspeicherung und Wasserstoffreinigung untersucht. Neue Erkenntnisse der Arbeit sind zum einen ein verbessertes Verständnis der Aktivierung des kommerziell erhältlichen und eingesetzten Ortho-Para-Katalysators Eisenoxid, verbunden mit einer kostenoptimierten Möglichkeit der Aktivierung und zum anderen die ersten Messungen der katalytischen Aktivität neuer kryogener Speichermaterialien auf Basis der Wasserstoffadsorption.

Faculty of Science; School of Chemistry; PhD Thesis / ortho-Ethoxy-trans-cinnamic acid (OETCA) has been known to form three polymorphs - the α , β and γ polymorphs which crystallize in P1 (Z=2), R3 (Z=18) and C2/c (Z=8), respectively. These polymorphs have long been of interest from polymorphism and solid-state photoreactivity perspectives but have, until now, never been fully characterized. In this thesis the complete structures of these polymorphs and their photodimerization products are presented. In addition, a new polymorph, the α' polymorph [P1 (Z=6)], which is only obtainable from the α polymorph via a reversible solid-state phase transformation at 60 °C, has been discovered and characterised. In all the polymorphs of OETCA, the smallest building component is the hydrogen-bonded carboxylic acid R22(8) dimers. These dimers further aggregate via CH...O interactions to form a ribbon motif in the α , α' and γ polymorph structures. Structural and solid-state reactivity differences in these three polymorphs are therefore due to differences in the arrangement of these ribbons. With few exceptions, solid state [2+2] photodimerization reactions have been found to obey the topochemical principle. Such reactions occur with minimal structural movement in which the contact distance between reacting double bonds is between 3.5 and 4.2 Å. In this respect the solid-state reactivity of both the α and α' polymorphs is especially interesting and unusual, and indicate that significant movement - both molecular and structural - is possible and necessary for reactions to occur in these polymorphs. Both polymorphs yield the centrosymmetric dimer product 2,2' diethoxy-α-truxillic acid. Photodimerization in the layered structure of the α polymorph, where the double bond contact distance is at 4.54 Å beyond reasonable photodimerization distance, is probably initially enabled by crystal defects. While the α' polymorph is structurally very similar to the α polymorph it is instead composed of two reaction sites with double bond contact distances of 3.72 and 4.99 Å, respectively. This polymorph's solid-state reactivity has as a consequence been found to be temperature dependent, with only 66.7% conversion being achieved at 293 K and 100% conversion occurring at 343 K; reaction at 343 K involves both a significant conformation change in a reaction product as well as a heat and reaction driven phase change. In the γ polymorph the closest distance between the double bonds is 5.26 Å, which together with the structural rigidity imposed by its herring bone structure ensures that no photodimerization occurs. The β polymorph is really a solvate containing either benzene or thiophene within channels in the structure. The interactions between the solvent and OETCA molecules play an important role in maintaining the symmetry and integrity of the structure. The thiophene and benzene forms of the β polymorph are isomorphous and yield a mirror product (2,2'-diethoxy-β-truxinic acid) upon photodimerization - the molecules involved being related by a 4.0 Å translation along the unit cell c axis.

1. FVP of arylmethylazides (33b¡B34b) via 3,3-sigmatropic rearrangement gave nitrogen-containing heterocyclic compounds (2b¡B4b). FVP of 35 gave 3-benzyl-2-thiophenecarbaldehyde (65) by 1,2 H shift of nitrene 32 followed by hydrolysis. 2. FVP of benzoic 3-(1-propenyl)-2-thiophenecarboxylic anhydride (67) gave 7-hydroxybenzo[b]thiophene (70) and cyclopenteno[b]thiophene (71). Compound 71 is difficult to synthesize by normal organic synthetic methods. The formation of 7-hydroxybenzo[b]thiophene (70) suggesting the existence of 68. 3. FVP of arylimine gave phenanthridine (3)¡B3-methylpyrrolo[2,3-c] quinoline (69) and thieno[2,3-c]quinoline (134). Such a method can synthesize tricyclic products in one step. On the other hand, photolytic study of arylimine gave compounds 156¡B184¡B164¡B180¡B185 and 186.

none