Search results for "bonds"
showing 10 items of 155 documents
Structures and energetic properties of 4-halobenzamides
2018
The amide bond represents one of the most fundamental functional groups in chemistry. The properties of amides are defined by amidic resonance (nN→π*C=O conjugation), which enforces planarity of the six atoms comprising the amide bond. Despite the importance of 4-halo-substituted benzamides in organic synthesis, molecular interactions and medicinal chemistry, the effect of 4-halo-substitution on the properties of the amide bond in N,N-disubstituted benzamides has not been studied. Herein, we report the crystal structures and energetic properties of a full series of 4-halobenzamides. The structures of four 4-halobenzamides (halo = iodo, bromo, chloro and fluoro) in the N-morpholinyl series h…
N,N-Dicyclohexylnitramine
2016
Molecules of the title compound, C12H22N2O2, are composed of an nitramine group substituted by two cyclohexane rings. The cyclohexane rings have chair conformations, with the exocyclic C—N bonds in axial orientations. In the crystal, C—H...O hydrogen bonds connect the molecules intoC(6) [-101] zigzag chains.
4-Fluoro-N-methyl-N-nitroaniline
2016
Molecules of the title compound, C7H7FN2O2, are composed of a nitramine group which is twisted with the respect to the aromatic ring, with an N—N—C—C torsion angle of −117.38 (12)°. In the molecule, the N—N bond length [1.3510 (15) Å] indicates some double-bond character, while the angle between the aromatic ring and the nitramine group rules out further delocalization in the molecule. In the crystal, C—H...F hydrogen bonds connect the molecules intoC11(6) chains along theaaxis. C—H...O hydrogen bonds form, which featureR22(12) loops and further connect these chains.
La persistance de la performance des fonds de pension individuels britanniques : une étude empirique sur des fonds investis en actions et des fonds o…
2003
Dans ce présent cahier de recherche, nous nous proposons d’étudier la stabilité des performances de certains fonds de retraite anglais à cotisations définies : les fonds de pension individuels (Personal Pension Scheme). Il s’agit de fonds – pratiquant une gestion active - investissant principalement dans les actions britanniques et de fonds détenant majoritairement des obligations anglaises durant la période novembre 1990 – novembre 2000. Les données sur les fonds de pension individuels proviennent de la base de données UK PENSION de Standard & Poor’s Fund Services et sont de fréquence mensuelle. Nous utilisons des tests paramétriques de l’existence de la persistance, plusieurs mesures de p…
Naratīva struktūra un galvenā tēla analīze Džeimsa Bonda filmās
2016
Par bakalaura darba “Naratīva struktūra un galvenā tēla analīze Džeimsa Bonda filmās” pētījuma problēmu tiek izvirzīta Džeimsa Bonda filmu apbrīnojamā popularitāte, tāpēc, lai noskaidrotu šo filmu panākumu cēloni, darba mērķis ir apskatīt Bonda filmām raksturīgo naratīva struktūru, filmas tēlus un to lomas, kā arī pašu galveno varoni. Darba teorija ir balstīta uz teorētiķu atziņām un pētnieciskajām iestrādnēm par populāro kultūru, naratīvu, žanru kā būtisku naratīva sastāvdaļu, formālistu naratīva studijām, kā arī kino valodas elementiem. Ar kvantitatīvās un kvalitatīvās kontentanalīzes un naratīvas analīzes palīdzību ir veikta analīze piecās Džeimsa Bonda filmās: “Zelta pirksts”, “Dzīvo un…
Inside Cover: Hydrogen-Bonded Open-Framework with Pyridyl-Decorated Channels: Straightforward Preparation and Insight into Its Affinity for Acidic Mo…
2017
International audience; A hydrogen-bonded open framework with pores decorated by pyridyl groups was constructed by off-charge-stoichiometry assembly of protonated tetrakis(4-pyridyloxymethyl)methane and [Al(oxalate)(3)](3-), which are the H-bond donor and acceptor of ionic H-bond interactions, respectively. This supramolecular porous architecture (SPA-2) has 1nm-large pores interconnected in 3D with large solvent-accessible void (53%). It demonstrated remarkable affinity for acidic organic molecules in solution, which was investigated by means of various carboxylic acids including larger drug molecules. Competing sorption between acetic acid and its halogenated homologues evidenced good sel…
Multifacial Recognition in Binary and Ternary Cocrystals from 5-Halouracil and Aminoazine Derivatives
2018
A systematic analysis using single crystal X-ray diffraction was performed to explore the role exerted by potential intercomponent proton-transfer reactions in the supramolecular structures of A–B cocrystals formed by 5-haloderivatives of uracil (A), coupled with 2-aminoadenine simulants (aminoazines, B). Twelve new heterodimers were synthesized in different stoichiometries and cocrystallized by solvent cogrinding followed by solution crystallization. In the binary cocrystals, uracil or 1-methyluracil with halide modification at the 5 position (F, Cl, Br, I) was coupled with amino-aromatic N-heterocycles (melamine, 2,4,6-triaminopyrimidine, 2,6-diaminopyridine) as a multivalent site for pyr…
L2 or L3? Foreign Language Enjoyment and Proficiency
2017
Enjoyment is among the achievement emotions encountered in school and university settings. While often identified with a sense of belonging not necessarily connected with learning (Lumby, 2011), foreign language enjoyment (FLE) in SLA has been found to correlate with teachers’ professional and affective skills, and the existence of a supportive peer group. The risk involved with meeting the challenges of the SLA process induces both private and social feelings of FLE (Dewaele & MacIntyre, 2016). This study hypothesizes that a good command of language may be a source of elevated levels of enjoyment, because greater language proficiency is connected with greater control perception, especially…
Functional molecular materials: supramolecular networks and coordination polymers with optical and/or magnetic properties
2020
El camp dels materials moleculars atrau l’atenció de molts científics degut al gran potencial de la química molecular en el disseny de materials amb un ajust precís de les seues propietats. Els dos projectes tractats en aquesta tesi representen dos temes que destaquen en aquesta àrea, materials de transició d’espín i polímers de coordinació amb propietats òptiques i/o magnètiques, gràcies al seu significant progrés i ràpid desenvolupament en els últims anys. La primera part d’aquesta tesi es basa en l’ús d’enllaços d’hidrogen en el disseny de xarxes multifuncionals de ferro(II) amb transicions d’espín abruptes. El capítol 1 és una introducció a aquest tema des de la perspectiva dels complex…
Crystal structure and Hirshfeld surface analysis of [N(CH3)4][2,2′-Fe(1,7-closo-C2B9H11)2]
2017
Abstract This work investigates the meta -ferrabis(dicarbollide) anion that was isolated as salt of tetramethylammonium. The structure of the obtained crystal consisted of discrete [2,2′-Fe(1,7- closo -C 2 B 9 H 11 ) 2 ] − anions and disordered [N(CH 3 ) 4 ] + cations. The anion had a considerable chemical stability ensured by ionic and Van der Waals interactions. Thus, Hirshfeld surfaces and fingerprint plot were used to visualize, explore, and quantify intermolecular interactions in the crystal lattice of the title compound. This investigation proved that close contacts were dominated by H⋯H interactions.