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Showing 1 to 20 of 22 for “"solvent effect"”.
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Supercritical Fluids: Kinetic Solvent Effect and the Correlation of Solid-Fluid Equilibria
… 378, 388, and 398 K in a supercritical propane solvent at pressures from 42 to 136 bar are presented. Data are presented for the cracking of dicyclopentadiene in supercritical butane at 433 K in the pressure range of 42-169 bar. Both reactions were studied in a supercritical chromatograph packed …
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Molecular insights on the solvent effect of methanol additive in glycine polymorph selection
… and design in organic crystallization, the effect of solvent on polymorph selection has gained tremendous interest in recent years. In this thesis, molecular simulation techniques are used to gain insight into the solvent effect on glycine crystallization in water-methanol mixtures. We …
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Nonideality of Single and Mixed Electrolyte Solutions Up to Moderately High Concentration; Theory Based on Debye-Huckel Radial Distribution Function
Because of the complex nature of the solvent effect and of the mathematical difficulty in the treatment of the Coulombic long-range force, the theoretical treatments of the equilibrium properties of the electrolyte solution are not fully developed if one compares with those of the non-electrolyte …
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Internal pressure's role in the selectivity of the bromine radical
… brominations and the internal pressure of solvent. The study encompassed l8 solvents and/or mixtures over which the rate constant ratio for SH2 ring opening of cyclopropylbenzene (kC) vs hydrogen abstraction from toluene (kH) by bromine atom was found to vary by nearly a factor of twenty as …
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Intermolecular interactions in supercritical fluid solutions from fluorescence spectroscopy
… including enhanced solubilities, synergistic effects of mixed solutes, and entrainer effects, may be explained by a region around the solute that has a higher density than the bulk. We present a new technique to investigae SCF's using fluorescence spectroscopy to probe the local interactions. …
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Spectroscopic Studies of Inclusion Host-Guest Complexes Between Cyclophane Corrals and Polcyclic Aromatic Hydrocarbons
Cyclophanes are macromolecules that are known to effectively bind with molecules to form host-guest complexes. Several cyclophane molecules, referred to as corrals (1-6) by their founders, have been synthesized. The characterization of these compounds and their complexes has been investigated using …
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La transposición N-ciclopropilimina-1-pirrolina
… a classical approach (products study, kinetics, solvent effect, selectivity, etc.) and from a theoretical point of view, to calculate energies of excited states, potential energy surfaces and conical intersections. As a result of this combined study, it can be concluded a whole mechanistic …
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I. The Reaction of Carboxylic/Thiocarboxylic Acids with Isonitriles II. Ruthenium Hydride Ring Opening of an Azetidinium Cation
… cal mol-1K-1 in toluene. There is a dramatic solvent effect: hydrogen bond accepting solvents retard the rate of the reaction by deactivation of the carboxylic acid. A plot of log(rate constant) vs beta (hydrogen bond acceptor basicity of the solvent) is a straight line with a substantial …
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A COMPUTATIONAL STUDY OF KETO-ENOL EQUILIBRIA OF CATECHOL IN GAS AND AQUEOUS SOLUTION PHASE
… Model (SCRF-PCM) was used to investigate the effect of an aqueous solvent on the extent of tautomerisation at the two above mentioned model chemistries. In addition, gas phase electronic and Gibbs free energies for the six molecules were computed using the CBS-QB3 method, and the G3 approach …
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Experimental and theoretical investigations of the dielectric and electro-optical properties of polycarbazoles and polysiloxanes
… in cyclohexane indicated a significant specific solvent effect. Theoretical investigations of the conformational statistics of cyclic and linear dimethyl siloxane oligomers and polymers have been undertaken. Rotational isomeric three-state models were used to calculate electric dipole moments, …
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Quantitative analysis of rocket propellant by capillary gas chromatography
… probes several of these possibilities. The effect on quantitation of: the solvent, the analysis time, and the use of splitless injection were investigated. Precision was shown to be improved by: 1. using a non-volatile solvent (toluene) rather than CH₂Cl₂, 2. using the most time-efficient …
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Influence of HLB of polysorbate surfactants on mobility of methazole in plants and soil
… with increasing concentration of methanol as a solvent and decreasing HLB values of surfactants. More ¹⁴C was translocated in cotton than in prickly sida. The effects of surfactants were masked by the drastic solvent action of 100% methanol. When the solvent effect was subtracted, the surfactant …
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Theoretical Study of Electron Transport and Trapping in Solvated Titanium Dioxide Nanoparticles
… DFT model (B3LYP), and a realistic treatment of solvent, we proposed an atomically detailed model for the electronic states involved in transport and trapping, and obtain good agreement with experiment for properties such as the energetics of the trapping states and the barriers to hopping …
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Structural studies of imidazolium and phosphonium cations with aprotic hetero cyclic anions (AHAs) and investigation of electrochemical CO₂ reduction
… basicity and geometry. We investigated the effect of hydrogen bonding in the selected ILs on chemical and physical properties by measuring and correlating the strength of hydrogen bonding with those chemical and physical properties. We found that the role of hydrogen bonding on the …
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Identities and Catalytic Functionalities of Reactive Hydrogen Species during Hydrogen Addition and Oxygen Removal Reactions of Carboxylic Acids, Carbonyls, and Phenols at Transition Metal-solvent Interfaces
At transition metal and protic solvent interfaces, H-adatoms (H*) derived from H2 (10-60 bar) dissociative adsorption, and protons (H+) derived from either H* ionization or solvent self-ionization are catalytically reactive H species. These H species participate in or assist with hydrodeoxygenation …
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Modulation of Hydroxyl Radical Reactivity and Radical Degradation of High Density Polyethylene
… is decidedly less reactive in an aprotic polar solvent than in aqueous solution. These findings are explained on the basis of a polarized transition state that can be stabilized via the hydrogen bonding afforded by water. Experimental and calculational evidence also suggest that the degree of …
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Investigations into the determination of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) by capillary gas chromatography
… , for PCBs) were studied, with emphasis on the effect of solvent. Having various volatilities and different polarities, solvent studied included dichloromethane, acetonitrile, hexan e, cyclohexane, isooctane, octane, nonane, dodecane, benzene, toluene, p-xylene, o-xylene, and mesitylene. …
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Lanthanide-based single-molecule magnets: A rational design by chemical intuition
… were carried out in order to investigate the effect of the chemical surroundings like aromaticity on the observation of single-molecule magnet (SMM) behaviour in a lanthanide-based complex (Dy1). Experimental techniques were combined with theoretical tools to investigate the dynamics of …
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Mechanism-Guided Studies of Brønsted Acid and Base Organocatalysis
… and the first-order rate constant for the solvent reaction (k0, s-1) for each imine were extracted from the rate-profiles, however, pKa values could not be obtained for reasons that will be discussed. Iminium ion pKa values were determined in dimethyl sulfoxide by adopting a bracketing …
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Rational Design of Supported Metal Catalysts for Carbonyl Reduction During Biomass Upgrading
… energies, and observed kinetic isotope effects over a large range of temperatures and concentrations (compound partial pressures) are reported in this document. Generally speaking, the ketone hydrogenation over metal surfaces in vapor phase comply with the mechanism that hydrogen atoms …
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