Solution-phase Reaction Research Articles

Simulating the Formation of Sodium:Electron Tight-Contact Pairs: Watching the Solvation of Atoms in Liquids One Molecule at a Time

The motions of solvent molecules during a chemical transformation often dictate both the dynamics and the outcome of solution-phase reactions. However, a microscopic picture of solvation dynamics is often obscured by the concerted motions of numerous solvent molecules that make up a condensed-phase environment. In this study, we use mixed quantum/classical molecular dynamics simulations to furnish the molecular details of the solvation dynamics that leads to the formation of a sodium cation-solvated electron contact pair, (Na(+), e(-)), in liquid tetrahydrofuran following electron photodetachment from sodide (Na(-)). Our simulations reveal that the dominant solvent response is comprised of a series of discrete solvent molecular events that work sequentially to build up a shell of coordinating THF oxygen sites around the sodium cation end of the contact pair. With the solvent response described in terms of the sequential motion of single molecules, we are then able to compare the calculated transient absorption spectroscopy of the sodium species to experiment, providing a clear microscopic interpretation of ultrafast pump-probe experiments on this system. Our findings suggest that for solute-solvent interactions similar to the ones present in our study, the solvation dynamics is best understood as a series of kinetic events consisting of reactions between chemically distinct local structures in which key solvent molecules must be considered to be part of the identity of the reacting species.

ChemInform Abstract: Metal@Silica Yolk‐Shell Nanostructures as Versatile Bifunctional Nanocatalysts

AbstractReview: 59 refs.

Growth and forms of spherulitic crystal pattern in a Belousov‐Zhabotinski type reaction system

AbstractThe growth of spherulitic like crystal patterns in a dual substrate Belousov–Zhabotinski (BZ) reaction system has been studied. The solution phase reaction has been found to show concentric ring like wave pattern. A colloidal phase consisting of numerous fine solid particles have also been observed during reaction process, which initially forms the solid phase nucleation centers of dendritic character, and subsequently grow into spherulitic like crystal patterns. The reaction mechanism has been proposed, which illustrate possible reaction products formed during solution phase reaction that are inevitably involved in the formation of the dendritic nucleation centers. The spherulitic crystal pattern has been found to show transition in morphology by substituted organic substrate.The transition behaviour of crystal pattern has also been described and discussed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Vibrationally Quantum-State–Specific Reaction Dynamics of H Atom Abstraction by CN Radical in Solution

Solvent collisions can often mask initial disposition of energy to the products of solution-phase chemical reactions. Here, we show with transient infrared absorption spectra obtained with picosecond time resolution that the nascent HCN products of reaction of CN radicals with cyclohexane in chlorinated organic solvents exhibit preferential excitation of one quantum of the C-H stretching mode and up to two quanta of the bending mode. On time scales of approximately 100 to 300 picoseconds, the HCN products undergo relaxation to the vibrational ground state by coupling to the solvent bath. Comparison with reactions of CN radicals with alkanes in the gas phase, known to produce HCN with greater C-H stretch and bending mode excitation (up to two and approximately six quanta, respectively), indicates partial damping of the nascent product vibrational motion by the solvent. The transient infrared spectra therefore probe solvent-induced modifications to the reaction free energy surface and chemical dynamics.

Tracking Degradations of Single DNA and Protein Molecules in Fluid

Moving images obtained from optical microscopic studies with single biomolecules, including DNA and proteins, provide amazing insights into physico-chemical fundamentals such as dynamics and kinetics in a particular environment. Previously, the observation of large numbers of individual molecules has been used to detect identifiable individual chemical events or components of a chemical synthesis system. These may offer crucial clues towards intricate molecular mechanisms. Despite this importance, analytical applications still have lagged behind the establishment of theoretical principles. Based on the Michaelis-Menten equation, values for the reaction rate constants have traditionally been calculated from the solution phase reaction kinetics. This procedure is predictably effective for discussing a minimal model of the kinetics. However, most biomolecular interactions are thought to involve multiple steps, typically an initial binding followed by a structural rearrangement. Particular attention should be given to the fractionally-sampled molecular steps. Our analysis, described here, uses a technology to determine the detailed molecular information about interactions between DNA and DNA interactive protein. It uses motion capture technology that was originally developed for recording biomechanical movement onto a digital model. We applied it for motion tracking and position sensing of a single DNA molecule undergoing restriction enzyme digestion in a microfluidic device. Quantum dot and total internal reflection fluorescence microscope were used as a marker and a tracker respectively, which allowed motion capture of DNA during interfacial reactions. With our analysis, an enzymatic degradation time was detected at a single molecule level. It was also possible to calculate the observed catalytic rate constant. As an application case of our tracking measurement, protease activity of trypsin was monitored in real time. The geometrical features of the biological process being studied reflect transient molecular actions that are otherwise inaccessible to traditional biochemical methods.

Syntheses, Crystal Structures, and Fluorescent Properties of Two Cation-induced Complexes: [(CdI4)(BPHX)] and [(Ag2I4)(BPHX)

In this article, the solution-phase reaction of metal iodides with BPHX yields two novel organic-inorganic hybrid mental iodides [(CdI4)(BPHX)] and [(Ag2I4)(BPHX)] (BPHX = 1, 6-bis(pyridinium)hexane dication), which are characterized by X-ray crystallography and IR spectroscopy. The title mononuclear compound 1 crystallizes in monoclinic, space group P2(1)/c with a = 9.7050(17) Å, b = 15.426(3)Å, c = 15.992(3) Å, α = 90○, β = 105.653(4), γ = 90○. Compound 2 crystallizes in orthorhombic, space group Fddd with a = 13.8931(10) Å, b = 22.2368(16) Å, c = 31.330(3) Å, α = 90○, β = 90○, γ = 90○. In the anion, each monovalent Ag atom is tetrahedrally coordinated by four μ2-I atom ligands to constitute an infinite 1D (Ag2I2− 4) anion chain with the organic dication BPHX ([C16H22N2]2+) trapped in it.

A Facile Route to Synthesize Gold Prisms Up to Micrometer Scale Based on Slow Reduction Methods

Gold prisms with edge length ranges from nanometer to micrometer scale were prepared in large quantities through facile liquid-liquid interfacial reaction and solution-phase reactions. The technological keys to synthesis of gold microprisms are (i) selecting poly(N-vinylpyrrolidone) (PVP) as the shape-directing agent to induce the preferential growth of nanoprism seeds and (ii) using weak reducing agents to lower the reduction rate of gold ions so that gold ions were reduced slowly onto the surface of the growing nanoprisms. Thus, the reduction of ions in the presence of PVP by some weak reducing agents generated a large number of gold microprisms (as defined by edge length of prisms). On the contrary, the relatively fast reduction of ions could only lead to formation of spherical gold particles.

Water-soluble dendritic-linear triblock copolymer-modified magnetic nanoparticles: preparation, characterization and drug release properties

One route has been employed to prepare dendritic-linear block copolymer modified superparamagnetic iron oxide nanoparticles (SPIONs), which consist of a Fe3O4 magnetic nanoparticle core and a dendritic-linear block copolymer, the focal point polyamidoamine-type dendron-b-poly(2-dimethylaminoethyl methacrylate)-b-poly(N-isopropylacrylamide) (PAMAM-b-PDMAEMA-b-PNIPAM) shell by two-step atom transfer radical polymerization (ATRP). Firstly, Fe3O4 nanoparticles were prepared by a high-temperature solution phase reaction in the presence of iron(III) acetylacetonate [Fe(acac)3], oleic acid and oleylamine. Then propargyl focal point PAMAM-type dendron (generation 2.0, denoted as propargyl-D2.0) with four carboxyl acid end groups as a cap displaced the oleic acid and oleylamine on the surfaces. Subsequently, an initiator for ATRP was introduced onto the propargyl-D2.0-modified Fe3O4 nanoparticle surfaces via click chemistry with 2′-azidoethyl-2-bromoisobutylate (AEBIB). PDMAEMA and PNIPAM were grown gradually from nanoparticle surfaces using two-step copper-mediated ATRP. Finally, a crosslinking reaction between PDMAEMA block with 1,2-bis(2-iodoethoxy)ethane (BIEE) was used to stabilize the nanoparticles and reverse aggregation. The modified nanoparticles were subjected to detailed characterization using FT-IR, DLS, XRD and TGA. Magnetization measurements confirmed the characteristic superparamagnetic behavior of all magnetic nanoparticles under room temperature. In addition, doxorubicin (DOX) as an anticancer drug model was loaded into the dendritic-linear block copolymer shell of the modified nanoparticles, and subsequently the drug release was performed in phosphoric acid buffer solution (pH 7.4) at 25 °C or 37 °C. The results verify that dendritic-linear block copolymer-modified nanoparticles as a drug carrier possess thermosensitive drug release behaviors. Furthermore, a methyl tetrazolium (MTT) assay of DOX-loaded dendritic-linear block copolymer-modified nanoparticles against Hela cells was evaluated. The results show that the modified nanoparticles can be used for drug delivery.

Hexagonal nanoplatelets of CuSe synthesized through facile solution phase reaction

A novel solution-phase synthetic route for obtaining hexagonal nanoplatelets of copper selenide is presented. Chemical reaction involved in the synthesis is the reduction of copper selenite with hydrazine hydrate. The reaction is performed in various solvents and in the presence of different capping agents. The structure, composition and properties of the nanomaterials obtained were studied with various techniques. The reduction reaction carried out in ethylene glycol even in the absence of any capping agents gave the best results. The relatively low temperature of reaction, usage of single precursor and the surfactant-free growth of nanomaterials make this synthetic route a promising one in perspectives of material science.

Covalent Modification of Gaseous Peptide Ions with N-Hydroxysuccinimide Ester Reagent Ions

Covalent modification of primary amine groups in multiply protonated or deprotonated polypeptides in the gas phase via ion/ion reactions is demonstrated using N-hydroxysuccinimide (NHS) esters as the modifying reagents. During the ion/ion reaction, the peptide analyte ions and the NHS or sulfo-NHS based reagent form a long-lived complex, which is a prerequisite for the covalent modification chemistry to occur. Ion activation of the peptide-reagent complex results in a neutral NHS or sulfo-NHS molecule loss, which is a characteristic signature of covalent modification. As the NHS or sulfo-NHS group leaves, an amide bond is formed between a free, unprotonated, primary amine group of a lysine side chain in the peptide and the carboxyl group in the reagent. Subsequent activation of the NHS or sulfo-NHS loss product ions results in sequence informative fragment ions containing the modification. The N-terminus primary amine group does not make a significant contribution to the modification process; this behavior has also been observed in solution phase reactions. The ability to covalently modify primary amine groups in the gas phase with N-hydroxysuccinimide reagents opens up the possibility of attaching a wide range of chemical groups to gaseous peptides and proteins and also for selectively modifying other analytes containing free primary amine groups.

ChemInform Abstract: Boron‐Based Dipolar Multicomponent Reactions: Simple Generation of Substituted Aziridines, Oxazolidines and Pyrrolidines.

AbstractNew multicomponent reactions of aldehydes, isocyanides, trialkylboron reagents, and dipolarophiles open the route to the title compounds using solution and solid phase reactions under mild conditions.

ChemInform Abstract: New Thermal Routes to ortho‐Benzyne

AbstractReview: 80 refs.

Oxidation Does Not (Always) Kill Reactivity of Transition Metals: Solution-Phase Conversion of Nanoscale Transition Metal Oxides to Phosphides and Sulfides

Unexpected reactivity on the part of oxide nanoparticles that enables their transformation into phosphides or sulfides by solution-phase reaction with trioctylphosphine (TOP) or sulfur, respectively, at temperatures of ≤370 °C is reported. Impressively, single-phase phosphide products are produced, in some cases with controlled anisotropy and narrow polydispersity. The generality of the approach is demonstrated for Ni, Fe, and Co, and while manganese oxides are not sufficiently reactive toward TOP to form phosphides, they do yield MnS upon reaction with sulfur. The reactivity can be attributed to the small size of the precursor particles, since attempts to convert bulk oxides or even particles with sizes approaching 50 nm were unsuccessful. Overall, the use of oxide nanoparticles, which are easily accessed via reaction of inexpensive salts with air, in lieu of organometallic reagents (e.g., metal carbonyls), which may or may not be transformed into metal nanoparticles, greatly simplifies the production of nanoscale phosphides and sulfides. The precursor nanoparticles can easily be produced in large quantities and stored in the solid state without concern that "oxidation" will limit their reactivity.

Metal@Silica yolk-shell nanostructures as versatile bifunctional nanocatalysts

Recent developments in nanochemistry offer precise morphology control of nanomaterials, which has significant impacts in the field of heterogeneous catalysis. Rational design of bifunctional catalysts can influence various aspects of catalytic properties. In this review, a new class of bifunctional catalysts with a metal@silica yolk-shell nanostructure is introduced. This structure has many advantages as a heterogeneous catalyst since it ensures a homogeneous environment around each metal core, and particle sintering is effectively eliminated during high temperature reactions. The catalysts exhibit high activity and recyclability in gas- and solution-phase reactions. It is anticipated that appropriate selection of bifunctional components and optimal structural control will significantly further enhance the catalytic properties, and enable target reaction-oriented development of new catalysts.

Physical and electrochemical characterization of CdS hollow microspheres prepared by a novel template free solution phase method

Novel CdS hollow microspheres have been successfully synthesized via a facile template-free solution-phase reaction from cadmium nitrate and thioacetamide precursors. The morphology of CdS hollow microspheres depends strongly on the ratio between the precursors, cadmium nitrate to thioacetamide ratio. The physical properties of the hollow microspheres have systematically been studied by different characterization methods. The stoichiometry of the hollow microspheres studied by the energy dispersive X-ray diffraction spectroscopy confirmed that the synthesized CdS hollow microspheres are nearly stoichiometric bulk like CdS. The morphology of the hollow microspheres studied by high resolution scanning electron microscopy and transmission electron microscopy observations showed that the CdS hollow microspheres of the size of 2.5 μm have hollow structure and are constructed by several nanoparticles of the size between 30 and 40 nm. The UV–visible diffuse reflectance spectroscopy studies showed that the band gap of the CdS hollow microspheres increased while increasing the cadmium nitrate to thioacetamide ratio. Further electrochemical characterization of CdS hollow microspheres was performed with glassy carbon electrode (GCE) after its chemical modification by CdS dispersed in dimethylformamide. The electrochemical studies showed that with decreasing the band gap energy the electron transfer resistance of CdS/GCE was also found decreased. Moreover, electrochemical impedance spectroscopic measurements showed enhanced DNA adsorption onto CdS/GCE in comparison to GCE. These experiments demonstrate that the CdS hollow microspheres act as an efficient electrode modifier that effectively decreased the charge transfer resistance and capacitance of the modified sensors, which can be used for electroanalytical purposes.

Liquid-Phase Synthesis of Biaryl Compounds by the Hydrogenolysis of Pentaerythritol-Supported Biarylsulfonates

Unfunctionalized biaryl compounds were parallelly and combinatorially prepared by the traceless hydrogenolysis of biarylsulfonates supported on pentaerythritol. The hydrogenolysis using 2-propylmagnesium chloride in the presence of <TEX>$dppfNiCl_2$</TEX> efficiently generated corresponding biaryl derivatives without any memory of the support. The strategy using pentaerythritol as a small soluble support was disclosed to have a potential to combine the benefits of both SPOS and solution-phase reaction with fast reaction rate, facile isolation of intermediates, easy analysis of intermediates and atom economical manner. The novel tetrapodal support is expected to be an efficient substitute for polymeric supports in many circumstances.

Mn3O4−Graphene Hybrid as a High-Capacity Anode Material for Lithium Ion Batteries

We developed two-step solution-phase reactions to form hybrid materials of Mn(3)O(4) nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Selective growth of Mn(3)O(4) nanoparticles on RGO sheets, in contrast to free particle growth in solution, allowed for the electrically insulating Mn(3)O(4) nanoparticles to be wired up to a current collector through the underlying conducting graphene network. The Mn(3)O(4) nanoparticles formed on RGO show a high specific capacity up to ∼900 mAh/g, near their theoretical capacity, with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn(3)O(4) nanoparticles grown atop. The Mn(3)O(4)/RGO hybrid could be a promising candidate material for a high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for the design and synthesis of battery electrodes based on highly insulating materials.

Lead Hydroxide Nanowires Obtained from Lead Nitrate Solution by Adding Chloride Ions

The synthesis of lead hydroxide nanowires by solution-phase chemical reactions of lead nitrate with alkali by adding sodium chloride was reported. The obtained lead hydroxide nanowires have a length of a few micrometers and a diameter of about several tens of nanometers. The selected-area electron diffraction reveals that these lead hydroxide nanowires are single crystalline. Controlled experiments indicate that lead hydroxide nanowires prefer to form at higher concentration of chloride ions in lead nitrate precursor solutions, such as Cl- : Pb2+ = 5:1 and 6:1.

Sunflower oil coating on the nanoparticles of iron(III) oxides

High-temperature solution phase reaction of iron(III)-furoate in sunflower oil, in the presence of trichloroacetic acid and 1,2-hexadecylamine leads to iron(III) oxide (amorphous and γ-Fe2O3) nanoparticles with sizes about 1.3 nm in diameter (method “A”), and about 5.5 nm (amorphous Fe2O3) from the “sunflower oil/oxadiazol” system (method “B”).

Catalytic peptide hydrolysis by mineral surface: Implications for prebiotic chemistry

The abiotic polymerization of amino acids may have been important for the origin of life, as peptides may have been components of the first self-replicating systems. Though amino acid concentrations in the primitive oceans may have been too dilute for significant oligomerization to occur, mineral surface adsorption may have provided a concentration mechanism. As unactivated amino acid polymerization is thermodynamically unfavorable and kinetically slow in aqueous solution, we studied mainly the reverse reaction of polymer degradation to measure the impact of mineral surface catalysis on peptide bonds. Aqueous glycine (G), diglycine (GG), diketopiperazine (DKP), and triglycine (GGG) were reacted with minerals (calcite, hematite, montmorillonite, pyrite, rutile, or amorphous silica) in the presence of 0.05 M, pH 8.1, KHCO 3 buffer and 0.1 M NaCl as background electrolyte in a thermostatted oven at 25, 50 or 70 °C. Below 70 °C, reaction kinetics were too sluggish to detect catalytic activity over amenable laboratory time-scales. Minerals were not found to have measurable effects on the degradation or elongation of G, GG or DKP at 70 °C in solution. At 70 °C pyrite was the most catalytic mineral with detectible effects on the degradation of GGG, although several others also displayed catalytic behavior. GGG degraded ∼1.5–4 times faster in the presence of pyrite than in control reactions, depending on the ratio of solution concentration to mineral surface area. The rate of pyrite catalysis of GGG hydrolysis was found to be saturable, suggesting the presence of discrete catalytic sites on the mineral surface. The mineral-catalyzed degradation of GGG appears to occur via a GGG → DKP + G mechanism, rather than via GGG → GG + G, as in solution-phase reactions. These results are compatible with many previous findings and suggest that minerals may have assisted in peptide synthesis in certain geological settings, specifically by speeding the approach to equilibrium in environments where amino acids were already highly concentrated, but that minerals may not significantly alter the expected solution-phase equilibria. Thus the abiotic synthesis of long peptides may have required activating agents, dry heating at higher temperatures, or some form of phase separation.