Kinetics of Crystalline Iodine Dissolution in Ethanol at Room Temperature and at 60°С

The kinetics of crystalline iodine dissolution in ethanol at room temperature and 60°C is studied using the electronic absorption spectra of iodine solutions. Dissolution is shown to proceed for more than three months. It is found that the process begins with the formation of hydroiodic acid HI and is complete with the formation of I ₃ ^? anions.     

The o-chlorotoluene photodissociation at 266 nm

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“Speed” Marvel at DuPont

Before beginning the technical subject, I'd like to take a few minutes to review Professor Marve?s long association with DuPont. Professor Marvel is known simply as “Speed” at DuPont, and I will refer to him by that title of respect. Speed has been a consultant for DuPont since February 1928, a little more than 55 years. In that time, we estimate he has made 260 trips to Wilmington or other DuPont locations from Urbana and Tucson, held 19,000 individual consulting conferences, stayed 1308 nights in the DuPont hotel (= 3.58 years), and surely, established many records for a consulting relationship, both in duration and breadth.     

Solid water at room temperature?

Previously, we have shown that water adjacent to many hydrophilic substances excludes colloidal and molecular solutes. It was labelled “exclusion zone” (EZ) or “fourth phase” water. A salient feature is its characteristic light absorbance at or near 270 nm. In this study, EZ water formed against three chemically distinct surfaces, Nafion, ghee, and Whatman-5 filter paper was extracted, characterized by UV–Visible absorbance spectroscopy, and solidified either by lyophilizing or evaporation in an oven. The resulting highly stable solid was dissolved in water and confirmed as EZ water by its characteristic absorbance at 270–280 nm. We used mass spectroscopy to verify the absence of ionizable contaminants that could reproduce the characteristic “signature EZ” spectra in the three liquid preparations, or in the solids formed from desiccated EZ water that had been reconstituted in deionized water. Hence, a solid form of EZ water may, indeed, exist at room temperature.     

Unexpected ipso-Substitutions at the β-Carboline Nucleus

Abstract

Minisci-type radical carbamoylation of 1-bromo-β-carboline (1) gives the 3-substituted product in low yield, whereas 1-acetyl-β-carboline (3a) reacts under ipso-substitution of the acetyl group. Cyanations of the N-oxides of 1 and 3a occur under clean ipso-substitution of the groups in 1-position. 1-Methyl derivatives show no tendency to react under ipso-substitution.     

Molecular electronics at electrode–electrolyte interfaces

Four contemporary examples, all published in recent years, of studies of molecular electronics at electrode–electrolyte interfaces are reviewed in this opinion article. The first illustrative example involves the switching of the redox active molecular wire between redox states, with concomitant changes in molecular conductance. This example illustrates how molecular electronics at electrode–electrolyte interfaces can be used to analyse mechanisms of electron transfer, to distinguish electrolyte effects and to provide details not readily available from ensemble measurements. The second example shows that the fluctuations of molecular conductance of a redox active molecular wire can be followed as a function of electrode potential. This shows how the stochastic kinetics of individual reaction events at electrode–electrolyte interfaces can be followed. The third example demonstrates how electrochemistry can be used to control quantum interference in single molecular wires. The fourth example shows a single-molecule electrochemical transistor concept for well-defined metal cluster containing molecular wires.     

Argon–water system at low temperatures

The molecular dynamics method is used to simulate argon solutions in water and a thin water film–argon system at low temperatures. The correlation in motions of two closely spaced argon atoms is of another nature than the correlation of two neon atoms in a neon solid solution in ice II. The structure of hydrate shells of argon atoms contains five-membered rings composed of water molecules. The solubility of argon in a water film at low temperatures is noticeably higher than at room temperature. If a water film is first cooled to the glassy state and then argon atoms are added to it, then approximately as many argon atoms are absorbed on the film surface as they are present in a cooled film in equilibrium with the argon atmosphere. Argon atoms migrate from one pit to another on the rough surface of a solid water film.     

Fat crystallisation at oil–water interfaces

This review focuses on recent advances in the understanding of lipid crystallisation at or in the vicinity of an interface in emulsified systems and the consequences regarding stability, structure and thermal behaviour. Amphiphilic molecules such as emulsifiers are preferably adsorbed at the interface. Such molecules are known for their ability to interact with triglycerides under certain conditions. In the same manner that inorganic crystals grown on an organic matrix see their nucleation, morphology and structure controlled by the underlying matrix, recent studies report a templating effect linked to the presence of emulsifiers at the oil/water interface. Emulsifiers affect fat crystallisation and fat crystal behaviour in numerous ways, acting as impurities seeding nucleation and, in some cases, retarding or enhancing polymorphic transitions towards more stable forms. This understanding is of crucial importance for the design of stable structures within emulsions, regardless of whether the system is oil or water continuous. In this paper, crystallisation mechanisms are briefly described, as well as recent technical advances that allow the study of crystallisation and crystal forms. Indeed, the study of the interface and of its effect on lipid crystallisation in emulsions has been limited for a long time by the lack of in-situ investigative techniques. This review also highlights reported interfacial effects in food and pharmaceutical emulsion systems. These effects are strongly linked to the presence of emulsifiers at the interface and their effects on crystallisation kinetics, and crystal morphology and stability.     

Cs3CoCl5 at 10 K

The crystal structure of tricaesium cobalt pentachloride has been determined by X-ray diffraction at 10 K. The Co atom is at a site with symmetry, one Cs atom is at a site with 42 symmetry, the other has mm site symmetry, one Cl ligand has 4/m symmetry and the other has m symmetry. The accurate and extensive data set collected should be suitable for charge–density analysis studies. In the CoCl₄²⁻ ion, as the temperature is lowered, the Co—Cl bond length increases a little and the small distortion of the tetrahedron (site symmetry 2m) is slightly reduced.     

Desorption/ionization of biomolecules from aqueous solutions at atmospheric pressure using an infrared laser at 3 μm

A new atmospheric pressure (AP) infrared (IR) matrix-assisted laser desorption/ionization (MALDI) ion source was developed and interfaced with a Thermo Finnigan LCQ ion trap mass spectrometer. The source utilized a miniature all-solid-state optical parametric oscillator (OPO)-based IR laser system tunable in the lambda = 1.5-4 microm spectral range and a nitrogen ultraviolet (UV) laser (lambda = 337 nm) for use in comparative studies. The system demonstrated comparable performance at 3 microm and 337 nm wavelengths if UV matrices were used. However, AP IR-MALDI using a 3 microm wavelength showed good performance with a much broader choice of matrices including glycerol and liquid water. AP IR-MALDI mass spectra of peptides in the mass range up to 2000 Da were obtained directly from aqueous solutions at atmospheric conditions for the first time. A potential use of the new AP IR-MALDI ion source includes direct MS analysis of biological cells and tissues in a normal atmospheric environment as well as on-line coupling of mass spectrometers with liquid separation techniques.     

σ-Cyclopropyl to π-Allyl Rearrangement at AuIII

The possibility for Au^III σ-cyclopropyl complexes to undergo ring-opening and give π-allyl complexes was interrogated. The transformation was first evidenced within (P,C)-cyclometalated complexes, it occurs within hours at −50 °C. It was then generalized to other ancillary ligands. With (N,C)-cyclometalated complexes, the rearrangement occurs at room temperature while it proceeds already at −80 °C with a dicationic (P,N)-chelated complex. Density Functional Theory (DFT) calculations shed light on the mechanism of the transformation, a disrotatory electrocyclic ring-opening. Intrinsic Bond Orbital (IBO) analysis along the reaction profile shows the cleavage of the distal σ(CC) bond to give a π-bonded allyl moiety. Careful inspection of the structure and bonding of cationic σ-cyclopropyl complexes support the possible existence of C−C agostic interactions at Au^III.     

Self-localized domain walls at π-conjugated branching junctions

Self-localized domain walls are found trapped at the potential wells created by π-conjugated branching junctions due to the intrinsic electron-phonon couplings. The potential well depths are 0.14 eV for soliton, 0.28 eV for polaron, and 0.32 eV for exciton using the adapted Su-Schrieffer-Heeger model Hamiltonian, as compared to 0.23 eV for soliton, 0.25 eV for positively charged polaron, 0.33 eV for negatively charged polaron, and 0.21 eV for exciton using the ab initio Hartree-Fock method. Once the junction trapping wells are filled, however, branching junctions turn repulsive to additional self-localized domain walls. Torsions around the branching junction center have significant effects on the junction band gap and electron localizations.     

Electrochemical Detection of Horseradish Peroxidase at Zeptomole Level

Horseradish peroxidase (HRP) is the archetypal heme peroxidase. The determination of HRP is considerably important in clinical chemistry and analytical biochemistry, because HRP is the commonly used enzyme label for immunological detection systems1. We developed a novel method based on its catalytic reaction. A capillary catalytic reaction system was designed (Figure 1). In the assay, both HRP and H2O2 are injected into the polyacrylamide-coated injection capillary (10) by electromig…     

Azetidine,pyrrolidine and hexamethyleneimine at 170 K

The crystal structures of the cyclic amines azetidine (C₃H₇N), pyrrolidine (C₄H₉N) and hexamethyleneimine (homopiperidine, C₆H₁₃N), of the series (CH₂)_nNH, with n = 3, 4 and 6, respectively, have been determined at 170 K, following in situ crystallization from the melt. These structures provide crystallographic data to complete the homologous series of cyclic amines (CH₂)_nNH, for n = 2–6. Azetidine and pyrrolidine contain chains propagating along 2₁ screw axes, in which the molecules are linked by co-operative N—H...N hydrogen bonds. Azetidine has two molecules in its asymmetric unit, while pyrrolidine has only one. Hexamethyleneimine contains tetrameric hydrogen-bonded rings formed about crystallographic inversion centres, with two molecules in its asymmetric unit. The observation of crystallographically distinct molecules in the hydrogen-bonded chains of azetidine and cyclic hydrogen-bonded motifs in hexamethyleneimine is consistent with expectations derived from comparison with monoalcohols forming chains or rings by co-operative O—H...O hydrogen bonds. The next member of the cyclic amine series, heptamethyleneimine, forms a cubic plastic phase on cooling from the melt.     

Tilting at Windmills? The Second Law Survives

The foundations of science might have been shaken by the “molecular ratchet” 1 . Designed to rotate preferentially in one direction it could, if successful, have threatened the Second Law of Thermodynamics. Sadly, but predictably, the Second Law was equal to the test.     

Effects of Cerium Doping at Ti Sites and Europium Doping at Ba Sites on Dielectric Properties of BaTiO3 Ceramics

IntroductionBarium titanate(BaTiO3or BT) is widely used asa capacitor material, because it is a simple compoundwith the highest permittivity. The dielectric constant atroom temperature is about 1600 for BaTiO3polycrys-tals[1]. However, barium titanate as …     

Micellar properties of tetradecyltrimethylammonium nitrate in aqueous solutions at various temperatures and in water-benzyl alcohol mixtures at 25 °C

The micellar properties of tetradecyltrimethylammonium nitrate (C14TANO₃) in aqueous solutions in the temperature range of 10 to 35 °C and in aqueous solutions of benzyl alcohol (BzOH) at 25 °C were studied conductometrically. The specific conductivity data served for the evaluation of critical micelle concentration, cmc, and the degree of ionization of the micelles, , of the surfactant. From the temperature dependence of the cmc the thermodynamic parameters for micellization of C14TANO₃ were calculated by applying Mullers modified equation. BzOH was found to affect strongly the cmc and values of the surfactant. The plot of the cmc/cmc_o ratio (where cmc_o is for pure water) as a function of BzOH molality, exhibits a characteristic break, which was attributed to the commencement of self-association of BzOH in aqueous solution at a molality of ca. 0.05. By applying the theoretical treatment suggested by Motomura for binary surfactant systems, the molar fraction of BzOH in the micelles at cmc, was estimated as a function of molality of the alcohol. C14TANO₃ appears to be slightly more hydrophobic compared to the corresponding bromide.     

Behavior of β-amyloid 1-16 at the air-water interface at varying pH by nonlinear spectroscopy and molecular dynamics simulations

The adsorption and aggregation of β-amyloid (1-16) fragment at the air-water interface was investigated by the combination of second harmonic generation (SHG) spectroscopy, Brewster angle microscopy (BAM), and molecular dynamics simulations (MD). The Gibbs free energy of surface adsorption was measured to be -10.3 kcal/mol for bulk pHs of 7.4 and 3, but no adsorption was observed for pH 10-11. The 1-16 fragment is believed not to be involved in fibril formation of the β-amyloid protein, but it exhibits interesting behavior at the air-water interface, as manifested in two time scales for the observed SHG response. The shorter time scale (minutes) reflects the surface adsorption, and the longer time scale (hours) reflects rearrangement and aggregation of the peptide at the air-water interface. Both of these processes are also evidenced by BAM measurements. MD simulations confirm the pH dependence of surface behavior of the β-amyloid, with largest surface affinity found at pH = 7. It also follows from the simulations that phenylalanine is the most surface exposed residue, followed by tyrosine and histidine in their neutral form.