Photonitration of aromatic compounds by tetranitromethane

This thesis describes the photochemical reactions of aromatic substrates with tetranitromethane. These reactions are known to proceed via the initial formation of a triad of species; the aromatic radical cation, trinitromethanide ion, and nitrogen dioxide. The chemistry of these systems involves the recombination of this triad. This thesis consists of five major parts. In the first (Chapter 2), the photochemical reactions of 1,5-dimethylnaphthalene with tetranitromethane are described. The initial step in the recombination of the triad is the reaction of trinitromethanide ion with the aromatic radical cation and this work highlights the importance of the resultant carbon radical stability to the reaction pathway. The isolation of a number of nitro-trinitromethyl adducts 221-224, 228-229, and hydroxy-trinitromethyl adducts 225-227, in addition to the thermal allylic rearrangement of adduct 228 to adduct 221 is documented. The second part (Chapter 3), discusses the photochemical reactions of 1-methoxynaphthalene with tetranitromethane. The effect of the methoxy substituent on the aromatic substrate is examined and the likely mode of formation of the trinitromethyl aromatic compound 309 and the nitro aromatic compound 306 via highly unstable intermediate adduct species is described. The identification of two labile nitro-trinitromethyl adducts 314 and 315 is also documented. The third part of this thesis (Chapter 4) describes the photochemical reactions of 4-methylanisole with tetranitromethane. A solvent induced change in the regiochemistry of trinitromethanide ion attack on the radical cation is rationalised in terms of the stabilisation of the trinitromethanide ion by more polar solvent environments. Evidence was obtained indicating that the nitrotrinitromethyl adducts 423 and 424 are formed via an allylic rearrangement of initially formed adducts 435 in competition with the formation of the observed nitro aromatic compound 420. The fourth part of this thesis (Chapters 5 and 6) describes the photochemical reactions of 2-methylanisole, 2,4-dimethylanisole, 4-fluoroanisole, and 4-fluoro-3-methylanisole with tetranitromethane. The effect of substitution of the aromatic substrate was explored and nitro-trinitromethyl adducts 518-519, 521-522, 617-623, and 634-636 identified. The final section of this thesis (Chapter 7) examines the effect of ethanol in the photolysis medium. The photochemical reactions of tetranitromethane with 1,2-dimethoxybenzene, 1,4-dimethoxybenzene, and 1,2-methylenedioxybenzene are described in addition to re-examination of the photochemical reactions of tetranitromethane with 1-methoxynaphthalene and 2-methylanisole in the presence of ethanol in the photolysis solution. Ethanol solvation of the trinitromethanide ion appears to retard nucleophilic attack on the aromatic radical cation in addition to introducing a sterically mediated change in the regiochemistry of trinitromethanide ion attack on the radical cation. A final feature of interest, the identification of highly labile nitro-trinitromethyl adducts 724 and 725 in the photolysis product mixtures of 1,4-dimethoxybenzene and tetranitromethane is also documented

Pure-shift IMPRESS EXSIDE:Easy measurement of ¹H-¹³C scalar coupling constants with increased sensitivity and resolution

Measuring long-range 1H–13C scalar coupling constants, nJCH, is made easier through improved sensitivity and resolution of the SelEXSIDE NMR experiment by incorporation of ‘pure-shift’ homonuclear decoupling and IMPRESS-Hadamard encoding.</p

Thermal reaction norms in sperm performance of Atlantic cod (Gadus morhua)

13 páginas, 6 figuras, 2 tablas[EN] Phenotypic plasticity occurs when a genotype produces variable phenotypes under different environments; the shapes of such responses are known as norms of reaction. The genetic scale at which reaction norms can be determined is restricted by the experimental unit that can be exposed to variable environments. This has limited their description beyond the family level in higher organisms, thus hindering our understanding of differences in plasticity at the scale of the individual. Using a three-year common-garden experiment, we quantify reaction norms in sperm performance of individual genotypes within different families of Atlantic cod (Gadus morhua). Cod sperm showed phenotypic plasticity in swimming performance across temperatures (3, 6, 11, and 21 °C), but the pattern of the response depended upon how long sperm had been swimming (30, 60, 120, or 180 s), i.e., plasticity in plasticity. Sperm generally swam fastest at intermediate temperatures when first assessed at 30 s after activation. However, a significant genotype × environment interaction was present, indicating inter-individual differences in phenotypic plasticity. To our knowledge, this is the first study to describe variable sperm performance across environmental conditions as a reaction norm. The results have potential theoretical, conservation, and aquaculture implications[FR] Il se produit une plasticité phénotypique lorsqu’un génotype détermine des phénotypes qui varient en fonction des différents environnements; les formes de telles réactions sont connues sous le nom de normes de réaction. L’échelle génétique à laquelle les normes de réaction peuvent être déterminées est restreinte par l’unité expérimentale qui peut être exposée à des environnements variables. Cela a limité leur description au-delà du niveau de la famille chez les organismes supérieurs, ce qui a entravé notre compréhension des différences de plasticité à l’échelle des individus. Dans une expérience de trois ans en jardin commun, nous avons mesuré les normes de réaction dans la performance des spermatozoïdes de génotypes individuels dans différentes familles de morues franches (Gadus morhua) de l’Atlantique. Les spermatozoïdes de morues font montre de plasticité phénotypique dans leur performance de nage sur une gamme de températures (3, 6, 11, et 21 8C), mais le patron de la réaction dépend du temps que le spermatozoïde a déjà consacré à la nage (30, 60, 120, ou 180 s), c’est donc une plasticité dans la plasticité. Les spermatozoïdes nagent généralement le plus vite aux températures intermédiaires lorsqu’ils sont évalués 30 s après leur activation. Cependant, il existe une interaction significative génotype environnement, ce qui indique qu’il y a des différences de plasticité phénotypique entre les individus. À notre connaissance, notre étude est la premiére à décrire une performance variable des spermatozoïdes comme des normes de réaction sur une gamme de conditions du milieu. Nos résultats ont des incidences théoriques potentielles, mais aussi des conséquences sur la conservation et l’aquacultureFunding was provided by a faculty startup award from Memorial University of Newfoundland to C.F.P., the Atlantic Cod Genomics and Broodstock Development Program and the Fisheries and Oceans Canada Aquaculture Collaborative Research Development Program to E.A.T., a scholarship from the Natural Sciences and Engineering Research Council of Canada to I.A.E.B, and a grant from Xunta de Galicia, inside de INCITE program, to A.A.- F. All animals were handled according to guidelines set by the Canadian Council on Animal CarePeer reviewe

Stimuli-responsive surfactants

Recent progress in stimuli-responsive surfactants is reviewed, covering control of both interfaces and bulk solution properties. Particular attention is devoted to potential future directions and applications

IMPRESSION – prediction of NMR parameters for 3-dimensional chemical structures using machine learning with near quantum chemical accuracy

The IMPRESSION (Intelligent Machine PREdiction of Shift and Scalar Information Of Nuclei) machine learning system provides an efficient and accurate route to the prediction of NMR parameters from 3-dimensional chemical structures. Here we demonstrate that machine learning predictions, trained on quantum chemical computed values for NMR parameters, are essentially as accurate but computationally much more efficient (tens of milliseconds per molecule) than quantum chemical calculations (hours/days per molecule). Training the machine learning systems on quantum chemical, rather than experimental, data circumvents the need for existence of large, structurally diverse, error-free experimental databases and makes IMPRESSION applicable to solving 3-dimensional problems such as molecular conformation and isomeris

Perhydrohelicenes and other diamond-lattice based hydrocarbons:The choreography of inversion

Overall inversion in fused cyclohexane oligomers 2, 3, and 4 (all based on cis-decalin 1) occurs by a rolling process involving no more than two adjacent rings in twist-boat conformations at any time.</p