Anhydrous Acetonitrile Research Articles

A Copper Cyanide Complex with Efficient Red Luminescence

Gaseous diffusion of diethyl ether into the solvothermal reaction mixture of copper cyanide (CuCN) with 2,2′-bipyridine (bipy) in anhydrous acetonitrile leads to a copper cyanide complex Cu(CN)(bipy) (1) with a special helical chain structure. Solid-state luminescence experiments show that complex 1 can emit efficient red luminescence, and its possible emission mechanism was investigated in detail based on theoretical calculations. The results may be helpful for the design and synthesis of more efficient luminescent materials.

Bismuth Triflate–Catalyzed Friedel–Crafts Acylations of Sydnones

Friedel–Crafts acylations of various 3-arylsydnones at the C4 position have been achieved in good yields using 4 equivalents of an alkyl anhydride and 25 mol% each of bismuth triflate and lithium perchlorate in anhydrous acetonitrile at 95 °C. Acylations appear to be faster with arylsydnones bearing electron-donating moieties and sterically unencumbered anhydrides.

Reaction of Phthalaldehyde with Aminoethanol under Different Conditions: Products and Mechanisms of Their Formation

Analysis of amino acids and very efficient disinfection procedures are based on the reaction of phthalaldehyde (OPA) with primary amines. In this contribution, aminoethanol (=kolamin) as a nitrogen‐containing nucleophile was used for the investigation of its reaction mechanism with OPA performed in basic aqueous buffered media (pH 9.5), where an influence of hydration or solvation is expected, and in anhydrous acetonitrile. Depending on the detailed reaction conditions, seven products were isolated and their structures determined by NMR, mass spectrometry, and X‐ray structure analysis. Reaction mechanisms are proposed, which involve hydride transfers to OPA (Cannizzaro‐type reaction). image

ChemInform Abstract: Synthesis of Fluorine‐Containing Allantoins, Hydantoins, and Oxazolones from Terminal Perfluoroolefin Oxides and Urea.

1,2-Epoxyoctafluorobutane reacted with urea in DMSO and aqueous DMSO, dioxane, and acetonitrile to give 40–42% of 5-hydroxy-5-pentafluoroethylimidazolidine-2,4-dione. 5-Hydroxy-5-tridecafluorohexylimidazolidine-2,4-dione was formed in 54% yield in analogous reaction of 1,2-epoxytridecafluorooctane with urea in aqueous DMSO. The reactions of 1,2-epoxyoctafluorobutane and 1,2-epoxytridecafluorooctane with urea in anhydrous dioxane and acetonitrile unexpectedly afforded heterocyclization products, 2-amino-5-fluoro-5-perfluoroalkyloxazol-4(5H)-ones (yield 11–82%). Fluorine-containing allantoin, 5-tridecafluorohexyl-5-ureidoimidazolidine-2,4-dione (yield 19%), and N-(1-hydroxy-2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)-urea (yield 46%) were synthesized for the first time by reaction of 1,2-epoxytridecafluoroctane with urea in DMSO and aqueous DMSO.

Anomalous solubility of oxygen in acetonitrile/water mixture containing tetra-n-butylammonium perchlorate supporting electrolyte; the solubility and diffusion coefficient of oxygen in anhydrous acetonitrile and aqueous mixtures

We report the oxygen electro-reduction in air-saturated acetonitrile (MeCN) solution supported by 0.1M tetra-n-butylammonium perchlorate salt under two experimental conditions: (1) anhydrous MeCN at elevated temperatures from 298.5 to 313.0K on platinum electrodes; (2) water-mixed MeCN solution (mole fraction of MeCN: 0.72<χMeCN<1) at 298.5K on glassy carbon electrodes. The measurements of diffusion coefficients and concentrations were determined via single and double potential step chronoamperometry at microdisc electrodes. The experimental results are analysed by Shoup and Szabo equation, or where necessary via simulation. Under the first experimental condition, the diffusion coefficients of oxygen, D(O2), and superoxide radical anion, D(O2-), at 298.5K are determined to be (9.20±0.36)×10−9m2s−1 and (2.73±0.35)×10−9m2s−1 respectively. Over the studied temperature range, the diffusional activation energies of oxygen (Ea,O2) and superoxide (Ea,O2−) are reported for the first time to be (2.07±0.05)kJmol−1 and (8.01±2.24)kJmol−1. The significant small value of Ea,O2 suggests the diffusional behaviour of molecular oxygen cannot be described by the Stokes–Einstein relationship; whereas that of the radical anion can be. This further confirms that the importance of the size of diffusional species must be at least comparable in size to that of the solvent molecules in order for this macroscopic theory to apply. Further, the concentration of dissolved oxygen, c(O2), is obtained as (1.26±0.05)mM, and the oxygen dissolution is quantitatively shown to be an endothermic process. The standard Gibbs energy of solvation (ΔGSolve) and the standard entropy change of solvation (ΔGSolve) are experimentally calculated to be +19.9 (error: +0.12/−0.11)kJmol−1 and −65.5 (error: +15.25/−12.62)Jmol−1K−1 respectively at 298.5K. Although the ΔGSolve for oxygen in water is much more positive than that in MeCN solution, an anomalous increase in oxygen solubility after the initial water-mixing with MeCN (0.94<χMeCN<1), under experimental condition (2), was observed. Over the same range of χMeCN, the D(O2) is found to drop in significant amount compared with its predicted value. Such behaviour can be tentatively explained by the preferential solvation of molecular oxygen by water molecules via hydrogen bonding at lower water content. Consequently, the thermodynamic terms of mixing may be altered, and therefore favour the dissolution of oxygen.

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

The reactions of sterically hindered amines (SHA) were investigated in acetonitrile solutions and TiO(2) suspensions upon exposure to monochromatic radiation, λ=365 nm, by means of in situ EPR spectroscopy. The formation of singlet oxygen, as one of the possible oxidation agents for SHA, in these systems is affected significantly by solvent used and the experimental conditions. Experiments in homogeneous media evidenced alternative pathways for the SHA oxidation with a variety reactive oxygen species involved. In anhydrous acetonitrile solutions containing KO(2), the SHA oxidation was negligible not only in the dark but also on continuous exposure. However, the presence of water, even at low concentrations, led to the transformation of O(2)(•-) to singlet oxygen and hydrogen peroxide, which served as a source of hydroxyl radicals. These species participated in oxidation of SHA resulting in the generation of nitroxide radicals. To investigate the influence of different competitive reactions of SHA with other ROS formed upon TiO(2) photoexcitation, a series of experiments using different additives (e.g. KO(2), H(2)O(2), NaN(3), dimethylsulfoxide, methanol as organic cosolvents) under air or argon were performed. The detailed analysis of paramagnetic intermediates formed upon the irradiation of the studied systems was accomplished using EPR spin trapping technique.

Decarboxylative aldol reaction catalysed by lipases and a protease in organic co-solvent mixtures and nearly anhydrous organic solvent media

The effects of the choice of lipase, reaction medium, immobilization, presence of additives and temperature on conversion and stereoselectivity during a lipase catalysed decarboxylative aldol reaction were examined. It was shown that Candida antarctica lipase B (CALB) catalysed a decarboxylative aldol reaction between 4-nitrobenzaldehyde and ethyl acetoacetate in a 60% acetonitrile–40% aqueous buffer co-solvent mixture. Interestingly, free and immobilized forms of CALB showed opposite enantioselectivity in this media. The addition of 30 mol% imidazole increased the reaction rate from 8.5 to 55.7 μM min− 1 mg− 1. A 98% conversion could be achieved in 14 h (instead of 168 h) by adding imidazole. Other lipases also catalysed this reaction in different reaction media to a varying extent. With Mucor javanicus lipase in 30% DMSO, 20% enantiomeric excess (ee) of the (R)-product was observed. CALB also catalysed this reaction in nearly anhydrous acetonitrile. In the presence of cross-linked protein coated microcrystals of CALB, 90% conversion was obtained in this media in 24 h. A commercially available protease, alcalase, was also found to catalyse this reaction. While low water media gave poor conversion, the reaction in aqueous–60% acetonitrile co-solvent mixture gave 99% conversion in 72 h, provided imidazole was used as an additive.

Electrospray Ionization Mass Spectrometric Analysis of Highly Reactive Glycosyl Halides

Highly reactive glycosyl chlorides and bromides have been analysed by a routine mass spectrometric method using electrospray ionization and lithium salt adduct-forming agents in anhydrous acetonitrile solution, providing salient lithiated molecular ions [M+Li]+, [2M+Li]+etc. The role of other adduct-forming salts has also been evaluated. The lithium salt method is useful for accurate mass determination of these highly sensitive compounds.

Highly regioselective heterocyclization reactions of 1H-1,2,4-triazole-3-thiols with chloroacetylenephosphonates

1-Chloroacetylene-2-phosphonates react with 1H-1,2,4-triazole-3-thiols in anhydrous acetonitrile with high regioselectivity to form the fused heterocycles, 6-(dialkoxyphosphoryl)-3H-thiazolo[3,2-b][1,2,4]triazol-7-ylium chlorides 1–5. A significant difference from the previously known reactions of binucleophiles with haloacetylenes is the involvement of both acetylenic carbon atoms in the heterocycle formation. A reaction mechanism is hypothesized that assumes the formation of a sulfenium cation at the acetylene C-1 atom followed by attack of the C-2 atom by the ring N-2 atom. Compounds 1–5 easily lose one alkyl group from the dialkoxyphosphoryl fragment to form zwitterions (e.g., 6–8) which further can be transformed into inner salts 9 and 10 when heated with concentrated hydrochloric acid.

The anthraquinone mediated one-electron reduction of oxygen in acetonitrile

We report the use of a boron-doped diamond electrode and the selection of an optimal anthraquinone derivative, to unambiguously investigate the one-electron mediated oxygen reduction mechanism, in an anhydrous acetonitrile solution. Cyclic voltammetric results were simulated and the rate of the electron transfer between the semi-quinone and oxygen species was found to be 7(±3)×106M−1s−1.

NMR and Electron Paramagnetic Resonance Studies of [Gd(CH3CN)9]3+ and [Eu(CH3CN)9]2+: Solvation and Solvent Exchange Dynamics in Anhydrous Acetonitrile

Homoleptic acetonitrile complexes [Gd(CH(3)CN)(9)][Al(OC(CF(3))(3))(4)](3) and [Eu(CH(3)CN)(9)][Al(OC(CF(3))(3))(4)](2) have been studied in anhydrous acetonitrile by (14)N- and (1)H NMR relaxation as well as by X- and Q-band EPR. For each compound a combined analysis of all experimental data allowed to get microscopic information on the dynamics in solution. The second order rotational correlation times for [Gd(CH(3)CN)(9)](3+) and [Eu(CH(3)CN)(9)](2+) are 14.5 ± 1.8 ps and 11.8 ± 1.1 ps, respectively. Solvent exchange rate constants determined are (55 ± 15) × 10(6) s(-1) for the trivalent Gd(3+) and (1530 ± 200) × 10(6) s(-1) for the divalent Eu(2+). Surprisingly, for both solvate complexes CH(3)CN exchange is much slower for the less strongly N-binding acetonitrile than for the more strongly coordinated O-binding H(2)O. It is concluded that this exceptional behavior is due to the extremely fast water exchange, whereas the exchange behavior of CH(3)CN is more regular. Electron spin relaxation on the isoelectronic ions is much slower than on the O-binding water analogues. This allowed a precise determination of the hyperfine coupling constants for each of the two stable isotopes of Gd(3+) and Eu(2+) having a nuclear spin.

A Comparative Nuclear Magnetic Resonance Study of the Solvation of CuClO4 in Binary Mixtures of Acetonitrile with Pyridine and Picolines at 298K

63Cu nuclear magnetic resonance (NMR) and viscosity studies of 0:064M CuClO4 solutions have been reported in binary mixtures of acetonitrile (AN) with pyridine (Py) and 2, 3, and 4-picolines (2,3,4-Pic) at 298 K using a Bruker 500 MHz NMR spectrometer and an Ubbelohde viscometer, respectively. Chemical shift d and linewidth D for the 63Cu signals have been recorded referenced to a 0:064M CuClO4 solution in anhydrous AN. The copper quadrupole coupling constants (e 2 Qq=h) have been calculated in all cases. The variation of the d and e 2 Qq=h values as a function of mol fraction of the co-solvent show that all these bases interact with Cu+ more strongly than AN. They replace AN from the Cu+ complexed with AN in the form [Cu(AN)4]+ and form a mixed complex of the type [Cu(AN)4-x(S)x]+ (x=1 - 4) where S stands for the base. At relatively high mole fraction of the co-solvents, the mixed solvated complex gradually changes to a more symmetrical complex of the type [Cu(S)4]+ which remains stable in the solution. The solvating effect of 2-Pic and 4-Pic is observed to be stronger than that of Py and 3-Pic.

Electro-synthesis and characterization of polythiophene nano-wires/platinum nano-particles composite electrodes. Study of formic acid electro-catalytic oxidation

The successful electro-synthesis of a composite made of polythiophene nano-wires and platinum nano-particles is reported. The nano-wires were prepared on a Pt electrode previously modified with a mesoporous silica thin film. The silica film modified electrode was also prepared and characterized by electrochemical means. For the electro-polymerization the working solution was 1.0×10−3molL−1 thiophene and 1.0×10−1molL−1 tetrabuthylammonium hexafluorophosphate in anhydrous acetonitrile. The nano-structured electrode was characterized and subsequently modified by dispersing platinum nano-particles employing an experimental method based on polymer doping properties. Also, electro-catalytic activity of the composite with respect to formic acid electro-oxidation was verified. The results were outstanding and compare well with those obtained employing a bare polycrystalline platinum electrode. The nano-wire deposit and the composite were analyzed by transmission electron microscopy, confirming the expected morphology and crystalline degree. All these results are of the utmost importance since only simple electrochemical preparative methods were utilized, allowing more control of the process and lowering production cost.

Synthesis of fluorine-containing allantoins, hydantoins, and oxazolones from terminal perfluoroolefin oxides and urea

1,2-Epoxyoctafluorobutane reacted with urea in DMSO and aqueous DMSO, dioxane, and acetonitrile to give 40–42% of 5-hydroxy-5-pentafluoroethylimidazolidine-2,4-dione. 5-Hydroxy-5-tridecafluorohexylimidazolidine-2,4-dione was formed in 54% yield in analogous reaction of 1,2-epoxytridecafluorooctane with urea in aqueous DMSO. The reactions of 1,2-epoxyoctafluorobutane and 1,2-epoxytridecafluorooctane with urea in anhydrous dioxane and acetonitrile unexpectedly afforded heterocyclization products, 2-amino-5-fluoro-5-perfluoroalkyloxazol-4(5H)-ones (yield 11–82%). Fluorine-containing allantoin, 5-tridecafluorohexyl-5-ureidoimidazolidine-2,4-dione (yield 19%), and N-(1-hydroxy-2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl)-urea (yield 46%) were synthesized for the first time by reaction of 1,2-epoxytridecafluoroctane with urea in DMSO and aqueous DMSO.

Structural and Photophysical Properties of Visible- and Near-IR-Emitting Tris Lanthanide(III) Complexes Formed with the Enantiomers of N,N′-Bis(1-phenylethyl)-2,6-pyridinedicarboxamide

The enantiomers of N,N'-bis(1-phenylethyl)-2,6-pyridinedicarboxamide (L), namely, (R,R)-1, and (S,S)-1, react with Ln(III) ions to give stable [LnL(3)](3+) complexes in an anhydrous acetonitrile solution and in the solid state, as evidenced by electrospray ionization mass spectrometry, NMR, luminescence titrations, and their X-ray crystal structures, respectively. All [LnL(3)](3+) complexes [Ln(III) = Eu, Gd, Tb, and Yb; L = (R,R)-1 and (S,S)-1] are isostructural and crystallize in the cubic space group I23. Although the small quantum yields of the Ln(III)-centered luminescence clearly point to the poor efficiency of the luminescence sensitization by the ligand and the intersystem crossing and ligand-to-metal energy transfers, the ligand triplet-excited-state energy seems relatively well suited to sensitize many Ln(III) ion's emission for instance, in the visible (Eu and Tb), near-IR (Nd and Yb), or both regions (Pr, Sm, Dy, Er, and Tm).

Buildup of Amphiphilic Molecular Bola from Organic–Inorganic Hybrid Polyoxometalates and Their Vesicle‐Like Supramolecular Assembly

Bisarylamines with o-alkoxy substituents [o-NH2-C6H4-O(CH2)1/2/3]2 react with [nBu4N]4[α-Mo8O26] in anhydrous acetonitrile in the presence of N,N′-dicyclohexylcarbodiimide (DCC) to form a series of nanoscale molecular bola, bisorganoimido-bridged hexamolybdates with flexible alterable lengths, in which two hexamolybdate cages are connected by the bisarylimido linkers (see scheme).

Pairing Heterocyclic Cations with closo-Icosahedral Borane and Carborane Anions, II: Benchtop Alternative Synthetic Methodologies for Binary Triazolium and Tetrazolium Salts with Significant Water Solubility

Two efficient processes for the synthesis of 12 relatively water-soluble binary triazolium and the first tetrazolium borane [B12H12] and carborane [CB11H12] salts by a one-step, open-air metathesis reaction have been developed. First, a combination of exhaustive trituration of the two solid reactant salts with refluxing anhydrous acetonitrile followed by flash filtration through a plug of silica gel afforded excellent recovery for a broad series of otherwise water-soluble heterocyclium salts. Second, an alternative aqueous metathesis, driven to completion by precipitation of silver halides, followed by removal of water, redissolution in acetonitrile, and filtration through a silica-gel plug, also yielded such heterocyclium borane and carborane salts. Mixed 1:1 dication heterocyclium borane salts were first synthesized using this second procedure, and one example showed melting-point depression behavior.

ChemInform Abstract: A Mild and Highly Efficient Catalyst for Beckmann Rearrangement, BF3·OEt2.

BF3·OEt2 (Boron trifluoride etherate), an inexpensive and commercially easily available Lewis acid stoichiometrically employed for Beckamann rearrangement in general, was now found to efficiently catalyze Beckmann rearrangement of ketoximes into their corresponding amides (up to 99% yield) in anhydrous acetonitrile under reflux temperature.

A Mild and Highly Efficient Catalyst for Beckmann Rearrangement, BF3·OEt2

AbstractBF3·OEt2 (Boron trifluoride etherate), an inexpensive and commercially easily available Lewis acid stoichiometrically employed for Beckamann rearrangement in general, was now found to efficiently catalyze Beckmann rearrangement of ketoximes into their corresponding amides (up to 99% yield) in anhydrous acetonitrile under reflux temperature.

In-source formation of N-acetyl- p-benzoquinone imine (NAPQI), the putatively toxic acetaminophen (paracetamol) metabolite, after derivatization with pentafluorobenzyl bromide and GC–ECNICI-MS analysis

Pentafluorobenzyl (PFB) bromide (PFB-Br) is a versatile derivatization reagent for numerous classes of compounds. Under electron-capture negative-ion chemical ionization (ECNICI) conditions PFB derivatives of acidic compounds readily and abundantly ionize to produce intense anions due to [M−PFB] −. In the present article we investigated the PFB-Br derivatization of unlabelled acetaminophen ( N-acetyl- p-aminophenol, NAPAP-d 0; paracetamol; MW 151) and tetradeuterated acetaminophen (NAPAP-d 4; MW 155) in anhydrous acetonitrile and their GC–ECNICI-MS behavior using methane as the buffer gas. In addition to the expected anions [M−PFB] − at m/ z 150 from NAPAP-d 0 and m/ z 154 from NAPAP-d 4, we observed highly reproducibly almost equally intense anions at m/ z 149 and m/ z 153, respectively. Selected ion monitoring of these ions is suitable for specific and sensitive quantification of acetaminophen in human plasma and urine. Detailed investigations suggest in-source formation of N-acetyl- p-benzoquinone imine (NAPQI; MW 149), the putatively toxic acetaminophen metabolite, from the PFB ether derivative of NAPAP. GC–ECNICI-MS of non-derivatized NAPAP did not produce NAPQI. The peak area ratio of m/ z 149 to m/ z 150 and of m/ z 153 to m/ z 154 decreased with increasing ion-source temperature in the range 100–250 °C. Most likely, NAPQI formed in the ion-source captures secondary electrons to become negatively charged (i.e., [NAPQI] −) and thus detectable. Formation of NAPQI was not observed under electron ionization (EI) conditions, i.e., by GC–EI-MS, from derivatized and non-derivatized NAPAP. NAPQI was not detectable in flow injection analysis LC–MS of native NAPAP in positive electrospray ionization (ESI) mode, whereas in negative ESI mode low extent NAPQI formation was observed (<5%). Our results suggest that oxidation of drug derivatives in the ion-sources of mass spectrometers may form intermediates that are produced from activated drugs in enzyme-catalyzed reactions.