Search results for "hexane"
showing 10 items of 467 documents
The electronic spectra of 2-(2′-hydroxybenzoyl)pyrrole and 2-(2′-methoxybenzoyl)pyrrole: a theoretical study
2005
The gas-phase electronic spectra of 2-(2 0 -hydroxybenzoyl)pyrrole and 2-(2 0 -methoxybenzoyl)pyrrole have been determined using multiconfigurational perturbation theory (CASPT2). Solvatochromic spectral shifts for these molecules have been measured in cyclohexane and methanol and the electrostatic components of these shifts have been estimated using the vertical electrostatic model (VEM 4.2) developed for the configuration interaction with single excitations model implemented with the intermediate neglect of differential overlap Hamiltonian (CIS/INDO/ S2). Comparison between theory and experiment and an interpretation of the main spectral differences between the two substituted pyrroles an…
The Influence of the Fir Absorption on the Dielectric Behaviour of Rigid Polar Molecules in Very Dilute Solutions
1974
In view of the FIR absorption the dielectric loss of ten polar molecules — with different volume between furan and 4-bromobiphenyl — has been measured in very dilute solutions at 11 fixed frequencies over an extended range from 0.3 to 300 GHz. Solvents are heptane, cyclohexane, mesitylene, and decalin. For these rigid polar molecules a second high frequency absorption region with time constants of 1–3 ps can be separated from the predominant Debye absorption. This additional absorption decreases with increasing Debye relaxation time. Various molecular motions contributing to this absorption are discussed.
Comparison of some dispersion-corrected and traditional functionals as applied to peptides and conformations of cyclohexane derivatives.
2012
We compare the energetic and structural properties of fully optimized α-helical and antiparallel β-sheet polyalanines and the energetic differences between axial and equatorial conformations of three cyclohexane derivatives (methyl, fluoro, and chloro) as calculated using several functionals designed to treat dispersion (B97-D, ωB97x-D, M06, M06L, and M06-2X) with other traditional functionals not specifically parametrized to treat dispersion (B3LYP, X3LYP, and PBE1PBE) and with experimental results. Those functionals developed to treat dispersion significantly overestimate interaction enthalpies of folding for the α-helix and predict unreasonable structures that contain Ramachandran φ and …
Iron(II) metallomesogens based on symmetrical tripod ligands
2012
Abstract Novel mononuclear tripodand-based iron(II) complexes showing liquid crystal properties have been synthesized and characterized. These are based on ligands tris[3-aza-4-((5-Cn)(6-R-2-pyridyl))but-3-enyl]amine, where R = hydrogen or methyl, 1,3,5-cis,cis-tris[1-aza-2-((5-alkyloxy)(2-pyridyl))vinyl]cyclohexane and 2,2,2-tris(2-aza-3-((5-alkyloxy)(2-pyridyl))prop-2-enyl)ethane. The physical characterization has been carried out by means of single-crystal X-ray diffraction measurements, magnetic susceptibility, differential scanning calorimetry, X-ray powder diffraction and Mossbauer spectroscopy.
Enantioselective sensing of dicarboxylates. Influence of the stoichiometry of the complexes on the sensing mechanism
2009
Two new cyclohexane-based thiourea chiral ligands have been synthesized in their enantiomerically pure forms. Both the ability of these ligands in the complexation of chiral dicarboxylates and their sensing properties have been studied. The influence of the stoichiometry of the formed complexes on the fluorescent properties of the systems has been established. The effect of additional substitution in the cyclohexyl moiety was considered by comparing the properties of the newly prepared ligands with those of similar compounds previously described.
From Hexaphenylbenzene to 1,2,3,4,5,6-Hexacyclohexylcyclohexane
2020
The hydrogenation of hexaphenylbenzene was studied, affording novel partially hydrogenated hexacyclohexylbenzene (HCB) as well as fully hydrogenated 1,2,3,4,5,6-hexacyclohexylcyclohexane (HCC) as an unprecedented “oligocyclohexyl” molecule. The reaction process was analyzed by mass spectrometry with atmospheric pressure chemical ionization and high-performance liquid chromatography. From a crude product mixture, two different crystals with flake- and block-shapes could be grown and analyzed by X-ray crystallography, revealing their structures as HCB and HCC. While a geared arrangement of cyclohexyl substitutes was found in HCB, two isomeric structures were identified in HCC crystal with cha…
Model for Solid State Voltammetry of Zeolite-Associated Species
2004
The electrochemical reduction/oxidation of zeolite-associated species is described from the model of Lovric and Scholz for redox conductive microcrystals and the model of Andrieux and Saveant for redox polymers. It is assumed that the reaction starts at the three-phase boundary between electrode, zeolite particle, and electrolyte. From this point, the reaction zone grows while electrons and charge-balancing cations diffuse perpendicularly along the zeolite. As a result, at short times, a Cottrell-type behavior, controlled by the diffusion of electrolyte countercations in the zeolite can be expected. At larger times, a thin-layer response in which electron hopping between adjacent redox site…
New Molecular Topologies by Fourfold Metathesis Reactions within a Hydrogen-Bonded Calix[4]arene Dimer
2003
A calix[4]arene tetrapentyl ether in the cone conformation substituted at its wide rim by four m-(omega-octenyloxy)phenyl urea groups forms hydrogen-bonded dimeric capsules in dichloromethane/benzene (95:5). Metathesis reaction with Grubbs' catalyst under high-dilution conditions (1.1 x 10(-4) M) followed by hydrogenation leads to a covalent connection of all the urea groups within a dimer. Three topologically different products may be expected in such a reaction: a bis[2]catenane, a doubly bridged monocatenane and a tetrabridged capsule. All three possible reaction products could be isolated in an overall yield up to 60 % for the separated and purified compounds. Their identification was b…
Fluorescent Sensing of Maleate versus Fumarate by a Neutral Cyclohexane Based Thiourea Receptor.
2006
A new cyclohexyl based fluorescent anion receptor, is able to recognize maleate versus fumarate both as their TMA salts. Costero Nieto, Ana Maria, Ana.Costero@uv.es ; Colera Llavata, Manuel, Manuel.Colera@uv.es ; Gaviña Costero, Pablo, Pablo.Gavina@uv.es ; Gil Grau, Salvador, Salvador.Gil@uv.es
(-)-(3a ' S,4 ' S,9b ' S,1R,2S,5R)-4 '-ethyl-3a ',4 ',5 ',7 ',8 ',9b '-hexahydro-2-isopropyl-5-methyl-2 '-phenylspiro[cyclo-hexane-1,7 '-dioxino[3,2-…
2005
The title compound, C27H33NO5, obtained from diethyl ether, crystallizes in space group P2(1) with four molecules in the asymmetric unit. The dioxinone and imide rings are almost planar, whereas the cyclohexane and cyclohexene rings form distorted conformations. The crystal structure confirms an earlier proposal about the stereoselectivity of Diels - Alder reactions to spirocyclic chiral 1,3- dienes.