Showing papers on "Acetonitrile published in 2011"

Palladium‐Catalyzed Oxidative Arylalkylation of Activated Alkenes: Dual CH Bond Cleavage of an Arene and Acetonitrile

Abstract: Not one but two: The title reaction proceeds through the dual C-H bond cleavage of both aniline and acetonitrile. The reaction affords a variety of cyano-bearing indolinones in excellent yield. Mechanistic studies demonstrate that this reaction involves a fast arylation of the olefin and a rate-determining C-H activation of the acetonitrile.

Viscosities of Acetate or Chloride-Based Ionic Liquids and Some of Their Mixtures with Water or Other Common Solvents

Abstract: For the temperature range (80 to 120) °C, viscosity data are reported for imidazolium-based ionic liquids 1-octyl-3-methylimidazolium chloride [Omim][Cl], 1-hexyl-3-methylimidazolium chloride [Hmim][Cl], 1-butyl-3-methylimidazolium chloride [Bmim][Cl], 1-ethyl-3-methylimidazolium chloride [Emim][Cl], 1-ethyl-3-methylimidazolium acetate [Emim][Ac], 1-butyl-3-methylimidazolium acetate [Bmim][Ac], and 1-butyl-3-methylimidazolium dicyanamide [Bmim] [N(CN)2]. Acetate-based ionic liquids have considerably lower viscosities than the corresponding chloride-based ILs. At 25 °C, viscosity data are reported for binary mixtures of [Bmim][Ac] with diluents water, acetonitrile, dimethylformamide (DMF), and ethylene glycol. Even a small concentration of diluent very much reduces the viscosity of an ionic liquid.

Electrochemical Properties of an All-Organic Redox Flow Battery Using 2,2,6,6-Tetramethyl-1-Piperidinyloxy and N-Methylphthalimide

Abstract: A novel all-organic redox flow battery employing 2,2,6,6-tetramethyl-1-piperidinyloxy/NaClO4/acetonitrile and N-Methyl- phthalimide/NaClO4/acetonitrile as catholyte and anolyte, respectively, is investigated by electrochemical measurements. The quasi-reversible and stable redox reactions are tested by cycle voltammetry. The diffusion coefficient of 0.02 M 2,2,6,6-tetramethyl-1-piperidinyloxy and 0.02 M N-Methylphthalimide in the supporting electrolyte are all in the range of 0.7–1.1× 10−5 cm2s−1 at room temperature. Stable charge-discharge curves and high coulombic efficiency (90%) for the first 20 cycles are obtained through charge-discharge test.

Solvent effect in the liquid-phase hydrogenation of acetophenone over Ni/SiO2: A comprehensive study of the phenomenon

Abstract: The solvent effect on catalyst activity and selectivity for the liquid-phase hydrogenation of acetophenone (AP) to 1-phenylethanol was thoroughly investigated over Ni/SiO2. Solvents of different nature were used: protic (C1–C3 primary and secondary alcohols), aprotic polar (tetrahydrofuran, γ-butyrolactone, and acetonitrile) and apolar solvents (cyclohexane, toluene, and benzene). The solvent had a strong influence on the AP hydrogenation rate but did not modify significantly the selectivity to 1-phenylethanol that was always higher than 92%. The AP hydrogenation activity followed the order: C2–C3 alcohols > cyclohexane > toluene > tetrahydrofuran > γ-butyrolactone > methanol ≫ benzene ≅ acetonitrile. In order to explain this activity pattern, the solvent–AP, solvent–H2 and solvent–catalyst interactions were analyzed. For the analysis of the solvent–AP interactions in liquid phase, both classical measures of polarity and others based on different solvatochromic scales were considered. The H2 availability in the liquid phase was estimated from the H2 solubility at reaction conditions. Solvent–catalyst interactions were characterized by means of the adsorption enthalpies measured calorimetrically. A reasonable correlation between the catalyst activity and some solvatochromic parameters was found only when solvents of similar nature were compared. For protic solvents, the AP hydrogenation rate decreased with the solvent polarity and its ability for H-bond formation with AP. Instead, the solvent–AP interactions were weak when using apolar solvents and thereby the activity pattern was essentially determined by the strength of solvent–catalyst interactions. In the case of aprotic polar solvents, both the solvent–AP interactions in the liquid phase and the solvent adsorption strength on the catalyst surface influenced the hydrogenation activity. The highest catalytic activities were obtained when using C2–C3 alcohol solvents. These protic solvents adsorbed dissociatively on metal nickel surface increasing the number of active H available for the hydrogenation reaction; this effect was much more important in the case of 2-propanol.

Association of ionic liquids in solution: a combined dielectric and conductivity study of [bmim][Cl] in water and in acetonitrile.

Abstract: Ion association of the ionic liquid [bmim][Cl] in acetonitrile and in water was studied by dielectric spectroscopy for salt concentrations c ≤ 1.3 M at 298.15 K and by measurement of molar electrical conductivities, Λ, of dilute solutions (c ≤ 0.006 M) in the temperature range 273.15 ≲ T/K ≤ 313.15. Whilst acetonitrile solutions of [bmim][Cl] exhibit moderate ion pairing, with an association constant of KoA ≈ 60 M−1 and increasing with temperature, [bmim][Cl] is only weakly associated in water (KoA ≈ 6 M−1) and ion pairing decreases with rising temperature. Only contact ion pairs were detected in both solvents. Standard-state enthalpy, entropy and heat capacity changes of ion association were derived, as well as the activation enthalpy of charge transport and the limiting conductivity of the cation, λ∞([bmim]+). These data, in conjunction with effective solvation numbers obtained from the dielectric spectra, suggest that the solvation of [bmim]+ is much weaker in water than in acetonitrile.

Anion‐Free Bambus[6]uril and Its Supramolecular Properties

Abstract: Methods for the preparation of anion-free bambus[6]uril (BU6) are presented. They are based on the oxidation of iodide anion, which is bound inside the macrocycle, utilizing dark oxidation by hydrogen peroxide or photooxidation in the presence of titanium dioxide. Anion-free BU6 was found to be insoluble in any of the investigated solvents, however, it dissolves in the presence of the tetrabutylammonium salt of a suitable anion. The highest association constant (8.9x10E5 1/M) was found for the 1:1 complex of BU6 with TBAI in acetonitrile/water mixture. A number of crystal structures of BU6 complexes with various anions were obtained.

Dinucleating Naphthyridine-Based Ligand for Assembly of Bridged Dicopper(I) Centers: Three-Center Two-Electron Bonding Involving an Acetonitrile Donor

Abstract: The three-center two-electron (3c-2e) bond is a well-known type of “electron-deficient” interaction that typically involves electron-poor main-group elements, such as aluminum or boron, in combination with strong s-donor ligands, such as hydride or alkyl ligands. However, 3c-2e bonds have also been observed for transition metals, for example in copper(I) aryl complexes in which the electron-deficient bond is supported by an unusually close Cu Cu contact (2.37– 2.45 ) indicative of a cuprophilic interaction. This attractive interaction between copper centers is reminiscent of the M M interactions observed in 3c-2e bonds of main-group metals. Over the past decade, similar cuprophilic interactions have been observed to result from 3c-2e bonds supported by unconventional L-type (two electron) donor interactions involving, for example, phosphole ligands. The latter complexes represent rare examples of a PR3 ligand coordinated in the m-h:h bridging mode. Herein we report the formation of a dicopper complex bridged by acetonitrile in this unusual m-h:h mode, whereby the bridging ligand formally contributes both electrons to the 3c2e interaction. The work discussed herein derives from an interest in dinuclear metal complexes for cooperative substrate activations in catalytic reactions. In particular, the use of dinucleating ligands with rigid frameworks may provide well-defined pockets that promote electronic communication between the metal centers and create selective binding sites for substrates, thereby emulating the role of the protein scaffold in enzymes. For this purpose we developed a ligand system based on 1,8-naphthyridine. The ligand 2,7-bis(1,1-dipyridylethyl)-1,8-naphthyridine (dpen) was synthesized by lithiation of 2,2’-dipyridylethane and subsequent reaction with 2,7dichloro-1,8-naphthyridine [Eq. (1)]. Ligands based on 1,8napthyridine have been shown to support a variety of

Bound states of the positron with nitrile species with a configuration interaction multi-component molecular orbital approach

Abstract: Characteristic features of the positron binding structure of some nitrile (-CN functional group) species such as acetonitrile, cyanoacetylene, acrylonitrile, and propionitrile are discussed with the configuration interaction scheme of multi-component molecular orbital calculations. This method can take the electron-positron correlation contribution into account through single electronic-single positronic excitation configurations. Our PA value of acetonitrile with the electronic 6-31++G(2df,2pd) and positronic [15s15p3d2f1g] basis set is calculated as 4.96 mhartree, which agrees to within 25% with the recent experimental value of 6.6 mhartree by Danielson et al. [Phys. Rev. Lett., 2010, 104, 233201]. Our PA values of acrylonitrile and propionitrile (5.70 and 6.04 mhartree) are the largest among these species, which is consistent with the relatively large dipole moments of the latter two systems.

Fluorescence PET (photo-induced electron transfer) sensor for water based on anthracene-amino acid

Abstract: An anthracene-amino acid system with two carboxyl groups has been designed and synthesized as a new class of fluorescence PET (photo-induced electron transfer) sensor for detection of water in organic solvents. An enhancement in fluorescence is observed with increasing water content in 1,4-dioxane, THF, acetonitrile and ethanol, which is attributable to the suppression of PET by the intramolecular proton transfer of the carboxyl proton to the amino group. The detection limit and quantitation limit are, respectively, 0.1 and 0.3 wt% for 1,4-dioxane, 0.4 and 1.2 wt% for THF, 0.1 and 0.3 wt% for acetonitrile and 0.1 and 0.3 wt% for ethanol.

Addition of amines and phenols to acrylonitrile derivatives catalyzed by the POCOP-type pincer complex [{κP,κC,κP-2,6-(i-Pr2PO)2C6H3}Ni(NCMe)][OSO2CF3]

Abstract: The pincer-type complex [{κP,κC,κP-2,6-(i-Pr2PO)2C6H3}Ni(NCMe)][OSO2CF3] (1) can serve as a precatalyst for the regioselective, anti-Markovnikov addition of nucleophiles to activated olefins. The catalyzed additions of aliphatic amines to acrylonitrile, methacrylonitrile, and crotonitrile proceed at room temperature and give quantitative yields of products resulting from the formation of C–N bonds. On the other hand, aromatic amines or alcohols are completely inert toward methacrylonitrile and crotonitrile, and much less reactive toward acrylonitrile, requiring added base, heating, and extended reaction times to give good yields. The catalytic reactivities of 1 are thought to arise from the substitutional lability of the coordinated acetonitrile that allows competitive coordination of the nitrile moiety in the olefinic substrates; this binding enhances the electrophilicity of the C C moiety, rendering them more susceptible to attack by nucleophiles. In some cases, RCN → Ni binding results in double bond isomerization/migration (allyl cyanide) or attack of nucleophiles at the nitrile moiety (cinnamonitrile and 4-cyanostyrene). Reaction of morpholine with 1 at 60 °C led to formation of the amidine derivative 2 that has been characterized by X-ray crystallography.

Acetonitrile-Templated Assembly of a Laminar Silver(I) Phthalate Coordination Polymer

Abstract: A novel infinite 2D silver(I) phthalate coordination polymer (CP), {CH3CN⊂[Ag2(pta)]4·CH3CN}n, (1, H2pta = phthalic acid) was synthesized and characterized. The flowerpot-shaped cavity in the sheet accommodates a linear acetonitrile molecule through quadruplex Ag···Nacetonitrile interaction. Using H2O as a solvent in the same preparative procedure, another silver(I) phthalate CP 2, {[Ag2(pta)(H2O)]}n, was isolated. Complex 2 is also a 2D sheet but does not include any solvent-occupied cavity. A comparative experiment shows that the acetonitrile acts as a template for the sheet formation. Moreover, the TGA and photoluminescence spectra of 1 and 2 were discussed.

Experimental investigation of nitrile formation from VUV photochemistry of interstellar ices analogs: acetonitrile and amino acetonitrile

Abstract: Context. The study of the chemical reactivity in interstellar ices in astrophysical environments is an important tool for understanding the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. The laboratory simulations of the reactivity in ice analogs provide important information for understanding the reactivity in these environments. Here, we used these experimental simulations to trace some formation pathways of two nitriles, acetonitrile and amino acetonitrile, which are two potential precursors of amino acids in astrophysical environments. Aims. The purpose of this work is to present the first experimental approach for the formation of acetonitrile and amino acetonitrile in interstellar-like conditions. Methods. We use Fourier Transform InfraRed (FTIR) spectroscopy and mass spectrometry to study the formation at 20 K of ace-tonitrile CH 3 CN from VUV irradiation of ethylamine and of amino acetonitrile NH 2 CH 2 CN from VUV irradiation of ammonia: acetonitrile mixture. Isotopic substitutions are used to confirm identifications. Results. We demonstrate that acetonitrile can be formed at 20 K from the VUV irradiation of ethylamine with a yield of 4%. Furthermore, in presence of ammonia, at 20 K and under VUV irradiation, the acetonitrile can lead to the amino acetonitrile for-mation. These results suggest that acetonitrile and amino acetonitrile can be formed in astrophysical environments that are submitted to VUV irradiations.

Iridium-catalyzed α-Alkylation of Acetonitrile with Primary and Secondary Alcohols

Abstract: Acetonitrile is successfully alkylated with primary and secondary alcohols in the presence of t-BuOK using [Ir(OH)(cod)]2 as a catalyst. This method provides a very clean and atom-economical conven...

Environmental effects on vibrational properties of carotenoids: experiments and calculations on peridinin

Abstract: Carotenoids are employed in light-harvesting complexes of dinoflagellates with the two-fold aim to extend the spectral range of the antenna and to protect it from radiation damage. We have studied the effect of the environment on the vibrational properties of the carotenoid peridinin in different solvents by means of vibrational spectroscopies and QM/MM molecular dynamics simulations. Three prototypical solvents were considered: cyclohexane (an apolar/aprotic solvent), deuterated acetonitrile (a polar/aprotic solvent) and methanol (a polar/protic solvent). Thanks to effective normal mode analysis, we were able to assign the experimental Raman and IR bands and to clarify the effect of the solvent on band shifts. In the 1500–1650 cm−1 region, seven vibrational modes of the polyene chain were identified and assigned to specific molecular vibrations. In the 1700–1800 cm−1 region a strong progressive down-shift of the lactonic carbonyl frequency is observed passing from cyclohexane to methanol solutions. This has been rationalized here in terms of solvent polarity and solute–solvent hydrogen bond interactions. On the basis of our data we propose a classification of non-equivalent peridinins in the Peridinin–Chlorophyll–Proteins, light-harvesting complexes of dinoflagellates.

Ionic association and solvation of the ionic liquid 1-hexyl-3-methylimidazolium chloride in molecular solvents revealed by vapor pressure osmometry, conductometry, volumetry, and acoustic measurements.

Abstract: A systematic study of osmotic coefficient, conductivity, volumetric and acoustic properties of solutions of ionic liquid 1-hexyl-3-methylimidazolium chloride ([C6mim][Cl]) in various molecular solvents has been made at different temperatures in order to study of ionic association and solvation behavior of [C6mim][Cl] in different solutions. Precise measurements on electrical conductances of solutions of [C6mim][Cl] in water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and acetonitrile at 293.15, 298.15, and 303.15 K are reported and analyzed with Barthel’s low-concentration chemical model (lcCM) to obtain the limiting molar conductivities and association constants of this ionic liquid in the investigated solvents. Strong ion pairing was found for the ionic liquid in 2-propanol, 1-butanol, and 1-propanol, whereas ion association in acetonitrile, methanol and ethanol is rather weak and in water the ionic liquid is fully dissociated. In the second part of this work, the apparent molar volumes and i...

A Simple Synthesis of Oxaphospholes

Abstract: Stable derivatives of oxaphospholes were obtained from the reaction between electron-deficient acetylenic compounds and phenacyl bromide or its derivatives in the presence of triphenylphosphine in acetonitrile as the solvent in excellent yields. GRAPHICAL ABSTRACT

Water versus acetonitrile coordination to uranyl. Density functional study of cooperative polarization effects in solution.

Abstract: Optimizations at the BLYP and B3LYP levels are reported for mixed uranyl-water/acetonitrile complexes [UO(2)(H(2)O)(5-n)(MeCN)(n)](2+) (n = 0-5), in both the gas phase and a polarizable continuum modeling acetonitrile. Car-Parrinello molecular dynamics (CPMD) simulations have been performed for these complexes in the gas phase, and for selected species (n = 0, 1, 3, 5) in a periodic box of liquid acetonitrile. According to structural and energetic data, uranyl has a higher affinity for acetonitrile than for water in the gas phase, in keeping with the higher dipole moment and polarizability of acetonitrile. In acetonitrile solution, however, water is the better ligand because of specific solvation effects. Analysis of the dipole moment of the coordinated water molecule in [UO(2)(H(2)O)(MeCN)(4)](2+) reveals that the interaction with the second-shell solvent molecules (through fairly strong and persistent O-H···N hydrogen bonds) causes a significant increase of this dipole moment (by more than 1 D). This cooperative polarization of water reinforces the uranyl-water bond as well as the water solvation via strengthened (UO(2))OH(2)···NCMe hydrogen bonds. Such cooperativity is essentially absent in the acetonitrile ligands that make much weaker (UO(2))NCMe···NCMe hydrogen bonds. Beyond the uranyl case, this study points to the importance of cooperative polarization effects to enhance the M(n+) ion affinity for water in condensed phases involving M(n+)-OH(2)···A fragments, where A is a H-bond proton acceptor and M(n+) is a hard cation.

The Role of Intermolecular Hydrogen Bonding and Proton Transfer in Proton-Coupled Electron Transfer

Abstract: An example of proton-coupled electron transfer (PCET) comprised by the electrochemical oxidation of 1,4-hydroquinone (1,4-H2Q) in acetonitrile was studied in the presence of Bronsted bases in acetonitrile. Of the two types of bases studied, the negatively charged carboxylates, trifluoroacetate (TFAC–), benzoate (BZ–), and acetate (AC–), showed hydrogen bonding with 1,4-H2Q, whereas the neutral amines, pyridine (PY) and N,N′-diisopropylethylamine (DIPEA), did not. This difference allowed a unique investigation of the effect of proton transfer on PCET with and without the influence of hydrogen bonding using two bases (TFAC– and PY) with approximately the same pKa (∼12). The study revealed that hydrogen bonding of 1,4-H2Q with the base TFAC– made the half wave redox potential of 1,4-H2Q more negative (easier to oxidize) by 0.186 V with respect to the oxidation in the presence of the same concentration of added PY, which does not hydrogen bond with 1,4-H2Q. Both types of bases studied, carboxylates and amines...

Synthesis, Characterization, and Analytical Applications of a New Composite Cation Exchange Material Acetonitrile Stannic(IV) Selenite: Adsorption Behavior of Toxic Metal Ions in Nonionic Surfactant Medium

Abstract: A composite cation exchange material acetonitrile stannic(IV) selenite was prepared under different experimental conditions. The ion exchange capacity of the material was improved from 0.75 to 1.83 meq g−1 in comparison to its inorganic counterpart, stannic selenite. The material was characterized on the basis of X-ray, TGA, FTIR, and SEM studies. Ion-exchange capacity, pH titration, elution behavior, and distribution studies were also carried out to determine the preliminary ion-exchange properties of the material. Furthermore, it was investigated that this ion exchange material has a good reusability after 8 times regeneration. The sorption behavior of metal ions was studied in nonionic surfactants namely triton x-100 and tween. On the basis of distribution coefficient studies, several binary separations of metal ions viz- Pb2+-Th4+, Ni2+-Th4+, Ni2+-Zn2+, Cu2+-Ce4+, Al3+-Bi3+, and Al3+Zn2+ was achieved on the packed column of this ion exchange material. The practical applicability of this cation-exchang...