Recent advances in the application of nanoparticles in the selective reduction of carbon–carbon double bonds

Herein, we present recent advances in the application of metal nanoparticles in the selective hydrogenation of C–C double bonds. The review focuses on reduction methods of alkenes, arenes, and aromatic heterocycles, which were classified according to transition metals used as catalysts. The majority of described systems concern direct hydrogenation, which is of particular importance to industrial processes. Nonetheless, interesting transfer hydrogenation protocols were also developed, which may be incredibly convenient for laboratory purposes. Some of the methods are distinguished with excellent chemoselectivity making them the perfect tool for the synthesis of compounds containing reducible functional groups. Apart from noble metals, the application of earth-abundant ones as catalysts was a subject of studies, and the related methods were highlighted.     

Direct observation of the “special” salt effect in the dynamics of transient ion pairs by time-resolved spectroscopy

Intimate ion pairs [A⁺,T⁻] are generated by specific excitation of the charge transfer band of the electron donor—acceptor complex of anthracene and tetranitromethane. Time-resolved spectroscopy in three distinct time regimes (ps, ns and μs) reveals the presence of a second “loose” or solvent-separated ion pair [A⁺//T⁻], the dynamic behavior of which is strongly modulated by added salts. The “special” salt effect is quantitatively evaluated, together with all the rate constants involved in ion-pair dynamics.     

Liquids intermediate between "molecular" and "ionic" liquids: liquid ion pairs?

Ionic liquids comprised of tetradecyltrihexyl- and tetrabutyl-phosphonium cations paired with chloride or sulfonyl amide anions exhibit properties that reflect strong ion association, including comparatively low viscosity as well as a degree of volatility, and hence exemplify an interesting intermediate state between true ionic and true molecular liquids.     

Vibrational study of the contact ion pair formation in the NaClO3–DMF system

Infrared and Raman studies of sodium chlorate in N,N-dimethylformamide (DMF) at different concentrations allowed to observe changes that are interpreted in terms of the contact ion pair formation. As the DMF is an ionising solvent it was possible to observe the equilibrium between associated and non-associated chlorate. In addition, depolarisation measurements were used to distinguish between the asymmetric and symmetric band representations in almost all regions of this anion. The vibrational assignment is entirely satisfactory indicating that in the Na⁺ClO₃⁻ contact ion pair the local symmetry around ClO₃⁻ changes from C_3v to C_S. In addition, our results do not show any evidence for the formation of solvent separated ion pairs and aggregates in this system.     

Structures and ambident reactivity of β-ketoenolates ion pairs

The relationships between the conformations and ambident reactivity of alkali ethylacetoacetate ion pairs are discussed.The structures of these enolates are determined in the solid state and in solution, in the presence of crown ethers and cryptands. The lithium ethylacetoacetate triple anion exhibits a peculiar structure and extra stability.     

Effect of the porosity of PS–DVB-copolymers on ion chromatographic behavior in inverse size-exclusion and ion chromatography

Small and highly pressure-stable PS-DVB copolymers of different porosity had been prepared by a two-step swelling procedure which enabled variation of diluent composition, an important characteristic affecting the porosity. The polymers were characterized by inverse size-exclusion chromatography and scanning electron microscopy. Subsequent chloromethylation and amination resulted in anion exchangers suitable for ion chromatography.The pore volume and the pore-size distribution is substantially affected by the fraction of the solvens component in the diluent. It was apparent from scanning electron microscopy that surface structure and the size of the polymer particles was not affected by diluent composition. The functionalization process led to a decrease in pore volume. The pore-size distribution remained unchanged during functionalization, which can be explained in terms of partial closing of all pore sizes. The chromatographic efficiency of the functionalized polymers in ion chromatography was highly dependent on diluent composition and the extent of functionalization was determined by the total pore volume.The composition of the diluent is an excellent tool for optimization of polymers used for the synthesis of surface-functionalized anion exchangers.     

Gas–solid interactions in the hydrogen/single-walled carbon nanotube system

Gas–solid interactions between hydrogen and single-walled carbon nanotubes (SWNTs) were investigated using highly purified SWNTs. The activation energy of hydrogen desorption, measured to be 0.21 eV, indicates that hydrogen is physisorbed in the pores and that inter-tube pores have an adsorption potential of about −0.21 eV, which induces hydrogen physisorption at ambient temperature. The total amount of adsorbed hydrogen, about 0.3 wt% at 9 MPa, shows that 38% of the inter-tube sites are occupied. These findings are interpreted in terms of the chemical potential of hydrogen and the adsorption potential of the inter-tube pores.     

DFT modeling of reactivity in an ionic liquid: How many ion pairs?

The modeling of reactivity in an ionic liquid is examined with DFT and DFT/MM calculations on the S(N)2 intramolecular rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole into 4-benzoylamino-2,5-diphenyl-1,2,3-triazole induced by amines. Experimental research has shown that the reaction occurs in 1-butyl-3-methylimidazolium tetrafluoroborate, and in conventional organic solvents such as acetonitrile with comparable rates. The structure for the reactants, transition states and products for the rate-determining step are optimized, and the energy barrier is computed in three different environments: gas phase, water solvent, and ionic liquid. The results are encouraging in describing the energy barrier in the ionic liquid. A simple model is formulated to explain the effect of the solvent in this particular process, and a procedure to study theoretically the reactivity in an ionic liquid is proposed.     

Electronic factor in electron self-exchange reaction of hydrated redox ion pairs from thermodynamic data

An accurate scheme for determining the electronic factor of the electron self-exchange reaction in solution is presented in this paper. The used various activation parameters and slopes of potential energy surfaces are obtained in terms of an improved activation model and the accurate potential function determined from the vibrational spectroscopic and thermodynamic data. The coupling matrix elements are determined using numerical integral method over the perturbed double-zeta Slater-type state functions. Theoretical results of electronic factor in this work are found in close agreement with those extracted from experimental rate constant data and to be less than unity. Results indicate that outer-sphere electron transfer reactions in solution involving hydrated transition metal ions are nonadiabatic in nature.     

Developments in ion mobility spectrometry–mass spectrometry

Ion mobility spectrometry (IMS) has been used for over 30 years as a sensitive detector of organic compounds. The following is a brief review of IMS and its principles with an emphasis on its usage when coupled to mass spectrometry. Since its inception, IMS has been interfaced with quadrupole, time-of-flight, and Fourier-transform ion cyclotron resonance mass spectrometry. These hybrid instruments have been employed for the analysis of a variety of target analytes, including biomolecules, explosives, chemical warfare degradation products, and illicit drugs.     

Hydrogen adsorption in the series of carbon nanostructures: Graphenes–graphene nanotubes–nanocrystallites

A comparative analysis of hydrogen absorption capability is performed for the first time for three types of carbon nanostructures: graphenes, oriented carbon nanotubes with graphene walls (OCNTGs), and pyrocarbon nanocrystallites (PCNs) synthesized in the pores of TRUMEM ultrafiltration membranes with mean diameters (D_m) of 50 and 90 nm, using methane as the pyrolized gas. The morphology of the carbon nanostructures is studied by means of powder X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy (TEM). Hydrogen adsorption is investigated via thermogravimetric analysis (TGA) in combination with mass-spectrometry. It is shown that only OCNTGs can adsorb and store hydrogen, the desorption of which under atmospheric pressure occurs at a temperature of around 175°C. Hydrogen adsorption by OCNTGs is quantitatively determined and found to be about 1.5% of their mass. Applying certain assumptions, the relationship between the mass of carbon required for the formation of single-wall OCNTGs in membrane pores and the surface area of pores is established. Numerical factor Ψ = m_dep/m_calc, where m_dep is the actual mass of carbon deposited upon the formation of OCNTGs and mcalc is the calculated mass of carbon necessary for the formation of OCNTGs is introduced. It is found that the dependence of specific hydrogen adsorption on the magnitude of the factor has a maximum at Ψ = 1.2, and OCNTGs can adsorb and store hydrogen in the interval 0.4 to 0.6 < Ψ < 1.5 to 1.7. Possible mechanisms of hydrogen adsorption and its relationship to the structure of carbon nanoformations are examined.     

Metal-free and selective cleavage of unstrained carbon–carbon single bonds: Synthesis of β-ketosulfones from β-chlorohydrins and sodium sulfinates

A metal-free protocol for the selective cleavage of unstrained C–C single bonds was developed. Under the catalysis of KI and in the presence of NaHCO₃, the readily available α-chloro-β-hydroxy ketones underwent bond breaking and sulfonylation smoothly to afford β-ketosulfones with high efficiency and broad substrate scope. Mechanism investigations, both experimental and theoretical, showed that a retro-aldol cleavage/nucleophilic substitution sequence might be involved.     

On the possibility of homolytic addition of N-bromohexamethyldisilazane to the triple carbon–carbon bond

Russian Journal of General Chemistry - By an example of a reaction of N-bromohexamethyldisilazane with phenylacetylene the possibility of its homolytic addition to the triple carbon-carbon bond...     

Enthalpic interaction coefficients of NaI–alkanediol pairs in methanol and in water

The dissolution enthalpies of NaI in the mixtures of methanol with 1,2-alkanediols (1,2-propanediol, 1,2-butanediol, 1,2-pentanediol) and with ??,??-alkanediols (1,3-propanediol, 1,4-butanediol, 1,5-pentanediol), as well NaI in the mixtures of water with 1,3-propanediol and 1,2-pentanediol, were determined at 298.15?K. The energetic effect of interactions between the investigated alkanediols and NaI in methanol and in water was calculated using the enthalpic pair interaction coefficients (h _xy ) model. These results along with the other data concerning the NaI?Cnon-electrolyte pairs taken from our earlier reports and from the literature were analyzed with respect to the effect of the non-electrolyte properties on the variations of the h _xy values. The group contributions illustrating the interactions of NaI with selected functional groups in non-electrolyte (alkanediol and alkanol) molecules, namely: CH₂ and OH groups were calculated and discussed.     

Test of the water adsorption model of organic electrocatalysis in the carbon monoxide–silver system in alkaline medium

A test has been carried out of the model of T. Iwasita, X.H. Xia, H.-D. Liess, W. Vielstich [J. Phys. Chem. B. 101 (1997) 7542], according to which the maximum at about the same potential in both the positive and negative sweeps in cyclic voltammograms (CVs) of small organic molecules on Pt is due to the concurrence of two processes with opposite potential dependences, adsorption of the organic compound and electrooxidation of its intermediates, which decrease and increase, respectively, with increasing potential. In turn, the decrease with increasing potential of the adsorption of the undissociated organic is due to its increasing displacement by molecular water, this competition occurring because the two molecular compounds have similar, low values of the adsorption energy. According to the model of T. Iwasita, X.H. Xia, H.-D. Liess, W. Vielstich [J. Phys. Chem. B. 101 (1997) 7542], with CO on Pt no anodic currents are observed in the negative sweep because of the high adsorption energy of CO on Pt, which precludes its displacement by water. Therefore, the model has been tested with the CO–Ag system, for which anodic currents should be observed in the negative sweep, since the adsorption energy of CO on Ag is very low. Effectively, this has been found to be the case, which indicates that the model is indeed applicable to the CO–Ag system over the tested pH range, 10–14. At pH⩽11 adsorbed CO was displaced from the surface of Ag by N₂ bubbling, while it was not at pH⩾12. However, even at pH⩾12 the adsorption energy of CO on Ag should be rather weak, since anodic currents appeared in the negative sweep in CO-saturated solution over the whole pH range tested, 10–14.     

Flow-injection analysis for the determination of total inorganic carbon and total organic carbon in water using the H2O2–luminol–uranine chemiluminescent reaction

In the presence of carbonate and uranine, the chemiluminescent intensity from the reaction of luminol with hydrogen peroxide was dramatically enhanced in a basic medium. Based on this fact and coupled with the technique of flow-injection analysis, a highly sensitive method was developed for the determination of carbonate with a wide linear range. The method provided the determination of carbonate with a wide linear range of 1.0 × 10⁻¹⁰–5.0 × 10⁻⁶ mol L⁻¹ and a low detection limit (S/N = 3) of carbonate of 1.2 × 10⁻¹¹ mol L⁻¹. The average relative standard deviation for 1.0 × 10⁻⁹–9.0 × 10⁻⁷ mol L⁻¹ of carbonate was 3.7% (n = 11). Combined with the wet oxidation of potassium persulfate, the method was applied to the simultaneous determination of total inorganic carbon (TIC) and total organic carbon (TOC) in water. The linear ranges for TIC and TOC were 1.2 × 10⁻⁶–6.0 × 10⁻² mg L⁻¹ and 0.08–30 mg L⁻¹ carbon, respectively. Recoveries of 97.4–106.4% for TIC and 96.0–98.5% for TOC were obtained by adding 5 or 50 mg L⁻¹ of carbon to the water samples. The relative standard deviations (RSDs) were 2.6–4.8% for TIC and 4.6–6.6% for TOC (n = 5). The mechanism of the chemiluminescent reaction was also explored and a reasonable explanation about chemical energy transfer from luminol to uranine was proposed. Figure Chemiluminescence profiles in batch system. 1, Injection of 100 μL of K₂CO₃ into 1.0 mL luminol-1.0 mL H₂O₂ solution; 2-3 and 4-5, Injection in sequence of 100 μL of K₂CO₃ and 100 μL of uranine into 1.0 ml luminol-1.0 mL H₂O₂ solution; C_luminol = 1.0 × 10⁻⁷ mol/L, C_H2O2 = 1.0 × 10⁻⁵ mol/L, C_uranine = 1.0 × 10⁻⁵ mol/L, C_K2CO3 = 1.0 × 10⁻⁷ mol/L except for 4-5 where C_K2CO3 = 1.0 × 10⁻⁴ mol/L     

Lanthanum ion–impregnated granular activated carbon for the removal of phenol from aqueous solution: Equilibrium and kinetic study

The current study discusses application of the lanthanum ions (La³⁺) as an activating agent incorporated /immobilized into coconut shell–based granular activated carbon (GAC) for porosity development; subsequently, the carbon material is used for the adsorption of phenol from aqueous solutions. The new carbons were characterized using FTIR, XRD, CHNO, burn off, and carbon yield. The surface functional groups were determined by Boehm titration. The Brunauer–Emmett–Teller (BET) surface area of the carbons is 953 m² g⁻¹ (GACLa1073), 997 m² g⁻¹ (GAC383), and 973 m² g⁻¹ (GACO383). Langmuir, Freundlich, Dubinin–Radushkevich, and John–Sivanandan Achari (J-SA) isotherm models on the equilibrium isotherm data were examined for the new carbon-phenol system. It is found that the Langmuir isotherm fits better with a monolayer adsorption capacity, highest for GACLa1073 (387.59 mg g⁻¹) followed by GAC383 (303.03 mg g⁻¹) and GACO383 (197.62 mg g⁻¹). Kinetic studies reveal that the adsorption system follows the pseudo–second-order kinetic model. Isotherm analysis by the phase change method of John-Sivanandan Achari (J-SA) isotherm gives a better insight into adsorption phenomena, which is accompanied by regeneration studies of carbon with >75% for GACLa1073 after three cycles.     

Measuring the rate constant of the reaction between carbon monoxide and iodine oxide at 298–363 K by the resonance fluorescence method

The rate constant of the reaction between the IO radical and carbon monoxide has been measured by the iodine atom resonance fluorescence method in the temperature range from 298 to 363 K. The reaction mainly takes place on the wall of the reactor.     

Plasmonics for the study of metal ion–protein interactions

The study of metal–protein interactions is an expanding field of research investigated by bioinorganic chemists as it has wide applications in biological systems. Very recently, it has been reported that it is possible to study metal–protein interactions by immobilizing biomolecules on metal surfaces and applying experimental approaches based on plasmonics which have usually been used to investigate protein–protein interactions. This is possible because the electronic structure of metals generates plasmons whose properties can be exploited to obtain information from biomolecules that interact not only with other molecules but also with ions in solution. One major challenge of such approaches is to immobilize the protein to be studied on a metal surface with preserved native structure. This review reports and discusses all the works that deal with such an expanding new field of application of plasmonics with specific attention to surface plasmon resonance, highlighting the advantages and drawbacks of such approaches in comparison with other experimental techniques traditionally used to study metal–protein interactions.

Effects of protonation on proton-transfer processes in guanine–cytosine Watson–Crick base pairs

Intermolecular proton-transfer processes in guanine–cytosine Watson–Crick base pairs have been studied using the B3LYP density functional method. Protonation of the base pair was carried out both at the N7 and at the O6 atoms of guanine. It is found that protonation induces a strengthening of the base pair and facilitates the N1–N3 single-proton-transfer reaction. The double-proton-transfer reaction, however, turns out to be unfeasible when the system is protonated at these sites. Mutagenic implications of these proton-transfer processes are discussed.Proceedings of the 11th International Congress of Quantum Chemistry satellite meeting in honor of Jean-Louis Rivail