Showing papers on "Acetonitrile published in 2008"
TL;DR: The enthalpy changes of 47 five-membered heterocyclic compounds (ZH) as a class of very important organic hydride donors to release hydrid anion were determined by using titration calorimetry and the result shows that theEnthalpy change scale of the 47 ZH in acetonitrile ranges from 49.0 to 93.4 kcal/mol, indicating that the ZH all should be weak hydrogen atom donors.
Abstract: The enthalpy changes of 47 five-membered heterocyclic compounds (ZH) [33 substituted 2,3-dihydro-2-phenylbenzo[d]imidazoles (1H-5H), 9 substituted 2,3-dihydro-2-phenylbenzo[d]thiazoles (6H), and 5 substituted 2,3-dihydro-2-phenylbenzo[d]oxazoles (7H)] as a class of very important organic hydride donors to release hydride anion were determined by using titration calorimetry. The result shows that the enthalpy change scale of the 47 ZH in acetonitrile ranges from 49.0 to 93.4 kcal/mol. Such a long energy scale evidently shows that the 47 ZH can construct a large and useful library of organic hydride donors, which can provide various organic hydride donors that the hydride-releasing enthalpies are known. The enthalpy changes of the 47 ZH to release hydrogen atom and the 47 ZH+• to release proton and hydrogen atom were also evaluated by using relative thermodynamic cycles according to Hess' law. The results show: (1) the enthalpy change scale of the 47 ZH to release hydrogen atom covers a range from 71.8 to ...
281 citations
TL;DR: In this article, a new class of CO2 binding organic liquids that chemically capture and release CO2 much more efficiently than aqueous alkanolamine systems was reported, and they have high CO2 capacities of up to 19% by weight for neat systems and slightly less when dissolved in acetonitrile.
Abstract: We report a new class of CO2 binding organic liquids that chemically capture and release CO2 much more efficiently than aqueous alkanolamine systems. Mixtures of organic alcohols and amidine/guanidine bases reversibly bind CO2 chemically as liquid amidinium/guanidinium alkylcarbonates. The free energy of CO2 binding in these organic systems is very small and dependent on the choice of base, approximately −9 kJ mol−1 for DBU and Barton's base and +2 kJ mol−1 for 1,1,3,3-tetramethylguanidine. These CO2 capturing agents do not require an added solvent because they are liquid, and therefore have high CO2 capacities of up to 19% by weight for neat systems, and slightly less when dissolved in acetonitrile. The rate of CO2 uptake and release by these organic systems is limited by the rate of dissolution of CO2 into and out of the liquid phase. Gas absorption is selective for CO2 in both concentrated and dilute gas streams. These organic systems have been shown to bind and release CO2 for five cycles without losing activity or selectivity.
256 citations
TL;DR: The fundamental aging mechanisms in double-layer capacitors based on alkylammonium electrolytes in acetonitrile were clarified for the first time in this article, where the authors showed that at cell voltages above 4 V, ultracapacitors cast out a crystalline mass of residual electrolyte, organic acids, acetamide, aromatics, and polymer compounds.
192 citations
TL;DR: In this article, the influence of solvent on the activity, epoxide selectivity, and H2O2 efficiency of three types of zeolites (TS-1, Ti-Beta, and Ti-MWW) in the liquid phase epoxidation of 1-hexene and cyclohexene was investigated.
136 citations
TL;DR: The results indicate that enhancement of the emission properties in pyridine is due to faster radiative rate related to formation of asymmetrical nine-coordinated structure, Sm(hfa)3(phen)(py) (py = p Pyridine).
Abstract: The effect of solvent molecule on the emission properties of Sm(hfa)3(phen)2 (hfa = hexafluoroacetylacetonato, phen = phenanthoroline) was investigated using acetone, acetonitrile, and pyridine. 5G(5/2) --> 5H(9/2) transition intensities in pyridine were found to be larger than those in corresponding acetone and acetonitrile. The radiative rate constant in pyridine (4.8 x 10(2) s(-1)) was 2 times larger than those in acetonitrile (2.6 x 10(2) s(-1)) and acetone (2.3 x 10(2) s(-1)), although the nonradiative transition via vibrational relaxation (k(nr) = 1.7 x 10(4) s(-1)) in pyridine was the same as those in acetone and acetonitrile (k(nr) = 1.8 x 10(4) s(-1)), resulting in the enhanced emission quantum yield of Sm(III) complex in pyridine (2.7%). The coordination structures of Sm(hfa)3(phen)2 in acetonitrile, acetone, and pyridine were estimated by X-ray single-crystal analyses. These results indicate that enhancement of the emission properties in pyridine is due to faster radiative rate related to formation of asymmetrical nine-coordinated structure, Sm(hfa)3(phen)(py) (py = pyridine).
121 citations
TL;DR: The dramatic decrease in the quantum yields on going from aprotic to protic solvents indicates the important role of solvent-solute hydrogen bonding in the nonradiative decay pathways.
103 citations
TL;DR: High resolution ESI-MS showed that reactions of carbonyls with methanol produce significant amounts of hemiacetals and acetals on time scales ranging from several minutes to several days, with the reaction rates increasing in acidified solutions.
Abstract: This study examined the effect of solvent on the analysis of organic aerosol extracts using electrospray ionization mass spectrometry (ESI-MS). Secondary organic aerosol (SOA) produced by ozonation of d-limonene, as well as several organic molecules with functional groups typical for OA constituents, were extracted in methanol, d3-methanol, acetonitrile, and d3acetonitrile to investigate the extent and relative rates of reactions between analyte and solvent. High resolution ESIMS showed that reactions of carbonyls with methanol produce significant amounts of hemiacetals and acetals on time scales ranging from several minutes to several days, with the reaction rates increasing in acidified solutions. Carboxylic acid groups were observed to react with methanol resulting intheformationofesters.Incontrast,acetonitrileextractsshowed no evidence of reactions with analyte molecules, suggesting that acetonitrile is the preferred solvent for SOA extraction. The use of solvent-analyte reactivity as a tool for the improved characterizationoffunctionalgroupsincomplexorganicmixtures was demonstrated. Direct comparison between mass spectra of the same SOA samples extracted in methanol versus acetonitrile was used to estimate the lower limits for the relative fractions of carbonyls (g42%) and carboxylic acids (g55%) in d-limonene SOA.
103 citations
TL;DR: In this article, an electrochemical modification of glassy carbon electrodes with 4-nitrophenyl, 4-bromophenyl and anthraquinone groups was characterized by cyclic voltammetry and the resulting grafted layer were characterized by electrochemical techniques.
99 citations
TL;DR: In this article, a one-pot multi-component reaction of aromatic aldehydes, enolizable ketones or β-keto esters and acetonitrile in the presence of acetyl chloride and 10−mol% ZnO nanoparticles for the synthesis of β-acetamido ketones/esters at room temperature is described.
93 citations
TL;DR: A heteroditopic receptor having crown ether and trifluoroacetylcarboxanilide groups selectively recognizes both potassium and cyanide ions in acetonitrile with an association constant of as high as Ka = 1.9 x 10(7) M(-1) through a highly cooperative ion-pair interaction, resulting in two orders of magnitude enhancement in the binding affinity.
91 citations
TL;DR: The accuracy of the methodology for two solvents of differing polarity indicates that this technique is suitable to study CN probes in proteins.
Abstract: The C≡N bond is a powerful probe of protein structure and dynamics because it absorbs in a region of the infrared spectrum apart from the other vibrations that occur naturally in proteins, and because its infrared absorption line shape is sensitive to specific characteristics of the local environment. Since the polarity experienced by the probe can differ dramatically within the protein, infrared spectroscopy of a C≡N site-specifically labeled residue can be used to infer its local environment within the protein. It has been shown experimentally that the spectrum of acetonitrile in water is different in terms of peak position and width compared to acetonitrile in tetrahydrofuran (THF). An optimized quantum mechanics/molecular mechanics method for calculating accurate vibrational frequencies in condensed-phase was parametrized for acetonitrile in water. The transferability of the methodology to a different solvent was tested by computing the infrared line shapes of acetonitrile in both water and THF and co...
TL;DR: The solubility of l-(+)-ascorbic acid in water, ethanol, methanol, propan-2-ol, acetone, acetonitrile, ethyl acetate, and tetrahydrofuran was measured by a gravimetrical method from (293 to 323) K as mentioned in this paper.
Abstract: The solubility of l-(+)-ascorbic acid in water, ethanol, methanol, propan-2-ol, acetone, acetonitrile, ethyl acetate, and tetrahydrofuran was measured by a gravimetrical method from (293 to 323) K, and the solubility data were correlated against temperature. The solubility of l-(+)-ascorbic acid in water and methanol was high compared with other solvents.
TL;DR: The reactivity of [LMnII]2+ toward addition of hydrogen peroxide (H2O2) in acetonitrile solution, where L is a pentadentate polypyridine ligand, offers new opportunities for the study of oxidation reactsivity of Mn (hydro)peroxo complexes.
Abstract: In the present work we report the reactivity of [LMnII]2+ toward addition of hydrogen peroxide (H2O2) in acetonitrile solution, where L is a pentadentate polypyridine ligand. Formation of peroxo complexes is evidenced by low-temperature UV–visible spectroscopy, ESI-mass spectrometry, and EPR spectroscopy using parallel as well as perpendicular mode detection. The influence of the medium (basicity, water content) on the formation of various species is investigated. In basic nonanhydrous medium the fate of the reaction mixture solution is the formation of the di-μ-oxo mixed-valent Mn(III)Mn(IV) dinuclear complex. In acidic medium the building of the oxo bridges is avoided and the reaction mixture evolves toward oxidation of the ligand L. This reaction route offers new opportunities for the study of oxidation reactivity of Mn (hydro)peroxo complexes.
TL;DR: Polysubstituted benzene derivatives with an unprecedented substitution pattern are produced in a novel one-pot multi-component cyclization reaction from pyridine, ethyl alpha-bromoacetate, malononitrile and aromatic aldehyde in refluxing acetonitrile.
TL;DR: In this article, a high molar extinction coefficient metal-free sensitizer composed of a triarylamine donor in combination with the 2-(2,2'-bithiophen-5-yl)acrylonitrile conjugation unit and cyanoacrylic acid as an acceptor was reported.
Abstract: We report a high molar extinction coefficient metal-free sensitizer composed of a triarylamine donor in combination with the 2-(2,2'-bithiophen-5-yl)acrylonitrile conjugation unit and cyanoacrylic acid as an acceptor. In conjugation with a volatile acetonitrile-based electrolyte or a solvent-free ionic liquid electrolyte, we have fabricated efficient dye-sensitized solar cells showing a corresponding 7.5% or 6.1% efficiency measured under the air mass 1.5 global sunlight. The ionic liquid cell exhibits excellent stability during a 1000 h accelerated test under the light-soaking and thermal dual stress. Intensity-modulated photocurrent and photovolatge spectroscopies were employed along with the transient photoelectrical decay measurements to detail the electron transport in the mesoporous titania films filled with these two electrolytes.
TL;DR: The fluorescence quenching of 7,8-benzo-4-azidomethyl coumarin by aniline has been studied in different solvent mixtures of benzene (BN) and acetonitrile (AN) at room temperature.
TL;DR: In this paper, a 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was used as a catalysts for the synthesis of propylene carbonate from propylene glycol and carbon dioxide in the presence of acetonitrile.
TL;DR: Three copper(II) Schiff-base complexes, [Cu(L1)(H2O)](ClO4) (1), [cu(L2)] (2) and [Cu (L3)] (3), have been synthesized and characterized by single crystal X-ray diffraction analysis.
TL;DR: Visible light excitation of Ru(bpz)(2)(deeb)](PF(6))(2), in acetonitrile solutions with iodide is shown to initiate excited-state electron transfer reactions that yield iodine atoms.
Abstract: Visible light excitation of [Ru(bpz)2(deeb)](PF6)2, where bpz is 2,2?-bipyrazine and deeb is 4,4?-(CO2Et)2-2,2?-bipyridine, in acetonitrile solutions with iodide is shown to initiate excited-state ...
TL;DR: Data from dynamic light scattering and transmission electron microscopy studies revealed that these binuclear platinum(II) complexes aggregated into nanosized particles in acetonitrile/water mixtures.
Abstract: A series of binuclear organoplatinum(II) complexes, [(tBu3tpy)Pt--(C[triple chemical bond]C--1,2-C6H4)n--C[triple chemical bond]C--Pt(tBu3tpy)][ClO4]2 (1-7, n=1, 2, 3, 4, 5, 6, 8; tBu3tpy=4,4',4''-tri-tert-butyl-2,2':6',2''-terpyridine) with foldable oligo(ortho-phenyleneethynylene) linkers were prepared and characterized by spectroscopic methods and/or X-ray crystallographic analyses. In the crystal structures of 32.5 CH3OH, 5CH3CN, and 64 CH3CN, each of the bridging ortho-phenyleneethynylene ligands has a partially folded conformation. In aerated water/acetonitrile mixtures with water percentages larger than 40 %, the emission of complexes 3-7 are red-shifted and enhanced when compared to those recorded in acetonitrile. The red-shift in emission energy and enhanced emission intensity can be attributed to the inter- and/or intramolecular interactions induced by the addition of water to solutions of the platinum(II) complexes in acetonitrile. Data from dynamic light scattering and transmission electron microscopy studies revealed that these binuclear platinum(II) complexes aggregated into nanosized particles in acetonitrile/water mixtures. Hydrophobic folding of the ortho-phenyleneethynylene linkers in acetonitrile/water mixtures is postulated.
TL;DR: In this article, gas evolution and associated pressure build up in supercapacitor devices were monitored using commercial electrode rolls and 1-mol/l solutions of TEABF 4 in acetonitrile (AN), propylene carbonate (PC), and γ-butyrolactone (GBL) during subsequent constant voltage periods (24h) at 25, 275,V, 30,V and 325,V.
TL;DR: In this article, aldehydes were oxidized to carboxylic acids at room temperature with 70% tert-butyl hydroperoxide (in water) in the presence of a catalytic amount of easily available ligand free CuCl in acetonitrile as solvent under very mild conditions.
TL;DR: To understand the vapochromic and vapoluminescent behaviors, crystal structures of both forms of PIr(qnx) are determined by X-ray diffraction and density functional theory is employed in investigating weak intermolecular interactions, such as hydrogen bonding and pi-pi interactions in the two forms.
Abstract: An iridium complex PIr(qnx) (iridium(III) bis(2-phenylpyridinato-N,C2)(quinoxaline-2-carboxylate)) is reported for its unique and fast vapochromic and vapoluminescent behaviors. The emission of PIr(qnx) is governed by the whole crystal rather than the individual molecule. PIr(qnx) has been found to exist as both black and red forms in the solid state. The black form can be transformed into the red form upon its exposure to acetonitrile or propiononitrile vapor, whereas no response was observed when it was exposed to other volatile organic compounds. To understand the vapochromic and vapoluminescent behaviors, we determined crystal structures of both forms by X-ray diffraction. In addition, we employed density functional theory in investigating weak intermolecular interactions, such as hydrogen bonding and π−π interactions in the two forms.
TL;DR: The results indicate that SECM is a very useful technique for studying electron transfer dynamics in ionic liquids in acetonitrile and in an ionic liquid electrolyte.
Abstract: The electrochemical behavior of a redox-active, ferrocene-modified ionic liquid (1-ferrocenylmethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) in acetonitrile and in an ionic liquid electrolyte (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) is reported. Reversible electrochemical behavior was observed in each electrolyte with responses typical of those for unmodified ferrocene observed in each medium. In the ionic liquid electrolyte, the diffusion coefficient of the redox-active ionic liquid increased by a factor of 5 upon increasing the temperature from 27 to 90 °C. The kinetics of electron transfer across the ionic liquid/electrode interface were studied using cyclic voltammetry, and the standard heterogeneous electron transfer rate constant, k0 was determined to be 4.25 × 10−3 cm s−1. Scanning electrochemical microscopy was then also used to probe the heterogeneous kinetics at the interface between the ionic liquid and the solid electrode and conventional kinetic SECM theor...
TL;DR: A simple and efficient electrocarboxylation reaction of aliphatic halides has been developed using silver as cathode, magnesium as anode and CH3CN saturated CO2 as solvent in an undivided cell.
TL;DR: In this paper, the Potasasium iodide (KI)/air/sodium nitrite (NaNO 2 ; cat.)/sulfuric acid (H 2 SO 4 ) iodinating system was used for the selective and efficient iodization of organic compounds.
Abstract: Selective and efficient iodinations of organic compounds were achieved by an aerobic oxidative process catalyzed by sodium nitrite using potassium iodide in acidic media. Using the potasasium iodide (KI)/air/sodium nitrite (NaNO 2 ; cat.)/sulfuric acid (H 2 SO 4 ) iodinating system, activated and moderately deactivated aromatic compounds were exclusively or preferentially iodinated at the para position. In protic solvents ketones and 1,3-dicarbonyl compounds were iodofunctionalized at the a carbonyl position, while in the case of aryl methyl ketones bearing an activated aromatic ring, the regioselectivity of iodination could be directed by the solvent used. In acetonitrile (MeCN) the aromatic ring was selectively iodinated, while in aqueous rethanol (EtOH) functionalization of the methyl carbon atom took place. Alkenes were transformed to vicinal iodohydrins or vicinal iodoalkoxy derivatives following Markovnikov-type regioselectivity and anti stereoselectivity, while 1,2-diiodoalkenes with preferentially E orientation were formed from alkynes.
TL;DR: In this article, the effects of feed concentration and feed temperature on the pervaporation performance, total and partial permeate fluxes as well as organic selectivity, have been investigated, and the overall mass transfer coefficients have been determined and discussed for each organic-water mixture at different conditions of feed temperature and initial organic feed concentrations.
TL;DR: The activation of aryl iodides and bromides by Cu(0)/1,10-phenanthroline in acetonitrile (S) generates Cu(I)(phenan Throline)S(2)(+) which can be a catalyst for cross-coupling reactions.
TL;DR: The experiments reveal that for both dyes, the polar protic solvent favors the aggregation process more than the aprotic solvent.
Abstract: Absorption, fluorescence, and fluorescence excitation spectral studies of two planar, cationic phenazinium dyes, namely, phenosafranin (PSF) and safranin-T (ST), have been performed in protic and aprotic polar solvents. The studies reveal the formation of both J- and H-aggregates in concentrated solutions. The planarity of the phenazinium skeleton and the presence of a positive charge are attributed to be the driving force for this aggregation behavior. The aggregates are established to be dimers only. The positive inductive effect of the methyl substituents in safranin-T augments the aggregation process. The experiments reveal that for both dyes, the polar protic solvent favors the aggregation process more than the aprotic solvent.
TL;DR: The balance of weak CH...N bonds involving the H 3C- and -CN groups has been related to the structural rearrangement between centrosymmetric and polar acetonitrile structures.
Abstract: The balance of weak CH···N bonds involving the H3C− and −C≡N groups has been related to the structural rearrangement between centrosymmetric and polar acetonitrile structures. The linear highly polar molecules arrange antiparallel in phase α below a freezing temperature of 225 K/0.1 MPa and above a freezing pressure of 0.38(5) GPa/296 K and in a polar mode in phase β below 206 K/0.1 MPa and at pressures higher than 0.63(5) GPa/296 K. The α ↔ β phase transition has been considered as a supramolecular reaction between 2-dimensional and 3-dimensional hydrogen-bonding networks, the latter favoring the polar association. Acetonitrile has been in situ pressure-frozen, and its structure has been determined at room temperature by single-crystal X-ray diffraction at 0.57(5), 0.63(5), and 1.50(5)GPa. The crystallization pressure at 296 K has been determined as 0.38(5) GPa both by ruby fluorescence in a diamond anvil-cell and by the compressibility measurement in a cylinder-and-piston device. Acetonitrile mixed with...