Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: CAS:75-05-8 (acetonitrile)
32,505 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Electrospray ionization can generate microsolvated multiply charged metal ions for various metals and ligands, allowing exploration of chemistry within such clusters. The finite size of these systems permits comparing experimental results with accurate calculations, creating a natural laboratory to research ion solvation. Mass spectrometry has provided much insight into the stability and dissociation of ligated metal cations. While solvated singly charged ions tend to shrink by ligand evaporation, solvated polycations below a certain size exhibit charge reduction and/or ligand fragmentation due to organometallic reactions. Here we investigate the acetone complexes of representative divalent metals (Ca, Mn, Co, Ni, and Cu), comparing the results of collision-induced dissociation with the predictions of density functional theory. As for other solvated dications, channels involving proton or electron transfer compete with ligand loss and become dominant for smaller complexes. The heterolytic C-C bond cleavage is common, like in DMSO and acetonitrile complexes. Of primary interest is the unanticipated neutral ethylene loss, found for all metals studied except Cu and particularly intense for Ca and Mn. We focus on understanding that process in the context of competing dissociation pathways, as a function of metal identity and number of ligands. According to first-principles modeling, ethylene elimination proceeds along a complex path involving two intermediates. These results suggest that chemistry in microsolvated multiply charged ions may still hold major surprises.
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PMID:Chemistry in acetone complexes of metal dications: a remarkable ethylene production pathway. 1750 88

Acetonitrile molecules are known for their intriguing ability to accommodate an excess electron in either a diffuse dipole-bound orbital, away from the valence electrons, or in its valence orbitals, depending on the environment. In this work, we report a computational investigation of the monomer and dimer acetonitrile anions, with the main goal of gaining further insight into the unusual electronic structure of these species. To this end, the topology of the electron density distribution has been examined in detail with the quantum theory of atoms in molecules (AIM). The excess electron is found to affect the topology of the electron density very differently for two dipole-bound-electron isomers of the acetonitrile dimer anion: for the head-to-tail isomer, the electron density simply decays away from the atomic nuclei, and the presence of the excess electron only manifests itself in the Laplacian of the electron density as a very diffuse region of "dipole-bound" charge concentration; in contrast, for the "solvated-electron" head-to-head isomer, a maximum of electron density without a corresponding atomic nucleus is observed, which topologically corresponds to a pseudo-atom of electron density. The acetonitrile dimer appears to be the smallest solvent cluster anion to exhibit such a non-nuclear attractor due to the presence of a solvated electron. Although the "solvated-electron" isomer is thermodynamically less stable than the head-to-tail isomer at 0 K, its floppy nature leads to a higher vibrational entropy that makes it the most stable acetonitrile dimer, anionic or neutral, above 150 K. As for the acetonitrile dimer anion with a valence-bound electron, its structure is characterized by acetonitrile molecules connected to each other at the cyanide carbon atoms; the AIM analysis reveals that, although this C-C bond is relatively weak, with an estimated bond order of 0.6, it possesses genuine covalent character and is not a "pseudo-bond" as previously speculated. We also report the first multireference electronic structure calculations of the valence-bound-electron acetonitrile monomer and dimer anions, the highest-level calculations of these species to date. The acetonitrile radical anion is unstable in the gas phase and is topologically characterized by a radical-like nonbonded charge concentration located at the cyanide carbon atom. Based on the results of the AIM analysis, the previously proposed resonance description of the valence-bound-electron acetonitrile anion is refined, and a new resonance description of the dimer anion is proposed. Overall, this work demonstrates the rich topological variety of the excess electron interacting with acetonitrile molecules, which manifests itself as charge concentrations, pseudo-atoms, and covalent bonds.
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PMID:Electronic structure of the acetonitrile and acetonitrile dimer anions: a topological investigation. 1815 88

We present here the results of a synchrotron radiation-excited UV-photoemission investigation and density functional theory calculations on a structurally related series of organometallic free molecules: ethylferrocene (EtFC), vinylferrocene (VFC), and ethynylferrocene (EFC). This series exemplifies the electronic interactions operating when the C-C substituent group of an aromatic ring is bound to the substrate surface atoms, from a single C-C bond to the double and triple C-C bond pi systems which are still able to preserve substrate-molecule conjugation. A detailed assignment of the gas phase valence photoelectron spectra is discussed, providing new data on the electronic structure of EtFC and EFC and offering a partial reinterpretation of previous assignments on VFC. The broken symmetry of ferrocene caused by the monosubstitution has notable effects on the removal of the molecular orbital (MO) degeneracy which is found to be especially remarkable for the ferrocenelike e(1)' MOs. This effect is ascribed to the interaction between the aromatic cyclopentadyenyl ring and the substituent through sigma/pi hyperconjugation and pi-conjugation mechanisms depending on the nature of the hydrocarbon moiety and its conformational geometry. The vertical ionization energy values of the highest occupied MO for the alkylferrocene and ferrocene free molecules linearly correlate with the redox potential in acetonitrile for ferrocene and the corresponding hybrids obtained by covalently anchoring the free molecule on silicon.
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PMID:Symmetry breaking effect in the ferrocene electronic structure by hydrocarbon-monosubstitution: an experimental and theoretical study. 1843 17

The RhIII complex [(PNP)Rh(CN)(CH3)][I] 5, obtained by oxidative addition of methyl iodide to [(PNP)Rh(CN)] 2, reacts selectively in two pathways: In aprotic solvents C-I reductive elimination of methyl iodide followed by its electrophilic attack on the cyano ligand takes place, giving the methyl isonitrile RhI complex [(PNP)Rh(CNCH3)][I] 3, while in protic solvents C-C reductive elimination of acetonitrile takes place forming an iodo RhI complex [(PNP)RhI] 9. Reaction of 2 with ethyl iodide in aprotic solvents gave the corresponding isonitrile complex, while in protic solvents no reactivity was observed. The selectivity of this reaction is likely due to a hydrogen bond between the cyano ligand and the protic solvent, as observed by X-ray diffraction, which retards electrophilic attack on this ligand.
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PMID:Competitive C-I versus C-CN reductive elimination from a Rh(III) complex. Selectivity is controlled by the solvent. 1884 93

Femtosecond time-resolved absorption anisotropy spectroscopy by multichannel detection has been developed. The charge transfer (CT) character and dynamics of the UV-photoexcited 9,9(')-bianthryl (BA) in heptane, acetonitrile, and ethanol are revealed with this method. The transient absorption spectra are decomposed into two absorption components with different anisotropy values by the absorption anisotropy spectra. The decomposition results show two absorption bands having different anisotropy values or different directions of the transition dipole moment. One band that has the transition dipole perpendicular to the central C-C bond has almost an identical spectral shape with transient absorption of anthracene in the singlet excited state. This band is assigned to a transition in a locally excited anthracene ring. The other band is broad and structureless. This band is assigned to partial charge transfer (PCT) absorption because its transition dipole moment is parallel to the central C-C bond. Because the PCT band is observed in a nonpolar solvent heptane as well as in polar solvents, the PCT occurs in both nonpolar and polar solvents. The PCT band rises within the instrumental response, indicating that the PCT takes place immediately after the photoexcitation. In acetonitrile, the CT component shows a significant blueshift, indicating the formation of the stabilized CT state from the PCT state. In ethanol, the CT band does not show a spectral shift, suggesting that the stabilization is smaller than in acetonitrile. From these results, a new kinetic model on the intramolecular CT in BA is discussed.
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PMID:Femtosecond time-resolved absorption anisotropy spectroscopy on 9,9'-bianthryl: detection of partial intramolecular charge transfer in polar and nonpolar solvents. 1914 Jun 16

Resonance Raman (RR) and resonance hyper-Raman (RHR) spectra have been obtained for a nominally centrosymmetric dialkylammonium-substituted distyrylbenzene that was previously shown to exhibit a strong solvent polarity effect on its two-photon absorption strength. Spectra have been obtained in acetonitrile, methanol, dimethylsulfoxide, and water. In each solvent, the RR and RHR spectra show very similar intensity patterns in the strongest lines in both the C=C and C-C stretching regions, but the RHR peaks are shifted to higher energies by 5-10 cm(-1). These are interpreted as vibrations of similar mode character but different symmetries, with u symmetry modes observed in RHR and g symmetry modes in RR. In all solvents the nonzero chromophore contribution to the hyper-Rayleigh scattering indicates that the center of symmetry is broken to some degree, and this effect is more pronounced in water than in the other three solvents. The ratio of RR intensity to one-photon fluorescence intensity shows an approximate inverse relationship with the fluorescence quantum yield, consistent with the approximate solvent independence of the one-photon transition strength implied by the linear absorption spectra. The ratio of RHR intensity to two-photon fluorescence intensity is smaller than the corresponding RR to one-photon fluorescence ratio in all four solvents.
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PMID:Solvent effects on resonance Raman and hyper-Raman scatterings for a centrosymmetric distyrylbenzene and relationship to two-photon absorption. 1919 92

A general approach to obtain pyrophosphonates is achieved by reacting arylphosphonic acids with AgNO(3) in CH(3)CN under solvothermal conditions; the process is coupled with the C-C bond cleavage of acetonitrile and the formation of novel complexes [Ag(n)(RPO(2)(O)O(2)PR)(m)](CN); the mechanism of the process is proposed.
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PMID:Ag(I)-mediated formation of pyrophosphonate coupled with C-C bond cleavage of acetonitrile. 1943 1

We previously reported that dinuclear copper(II) cryptate [Cu(2)L](4+) cleaves the C-C bond of acetonitrile at room temperature to produce a cyano-bridged dinuclear cryptate and methanol, whereby the reaction mechanism has not yet become clear. We have now systemically investigated this reaction, and four cryptates, [Cu(2)L](ClO(4))(4) (1), [Zn(2)L](ClO(4))(4) (2), [Cu(2)L(H(2)O)(2)](CF(3)SO(3))(4) (5), and [Cu(2)L(OH)(OH(2))](ClO(4))(3) (6) are reported here. Cryptates 1 and 2 can cleave the C--C bonds of acetonitrile, propionitrile, and benzonitrile at room temperature under open atmospheric conditions to give cyano-bridged cryptates [Cu(2)L(CN)](ClO(4))(3) (3) and [Zn(2)L(CN)](ClO(4))(3) (4), respectively, and the corresponding alcohol. In contrast, 5 and 6 do not show any C-C bond activation of nitriles, as the interior axial positions of Cu(II) in 5 and 6 are occupied by water/OH(-). The C-C bond cleavage of (S)-(+)-2-methylbutyronitrile by 2 produced (R)-(-)-2-butanol only; that is, the cleavage reaction proceeds through an S(N)2 pathway (Walden inversion).
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PMID:Mechanistic studies of C-C bond cleavage of nitriles by dinuclear metal cryptates. 1981 59

The electrochemical polymerization of N-ethyl carbazole (EK) on carbon nanotubes (CNs) films immersed in a LiClO4/acetonitrile solution was studied by cyclic voltammetry. Cyclic voltammograms recorded on a blank Pt electrode were compared with those obtained when CNs films were deposited on a Pt plate. In the latter case, the oxidation maximum is not clearly observed. Using the Raman scattering studies, oligomers of poly(N-ethyl carbazole) (PEK) on CNs are shown to be formed. A covalent functionalization of CNs with the PEK oligomers is demonstrated by FTIR spectroscopy studies. The formation of new C-C covalent bonds between CNs and the benzene ring of PEK induces steric hindrance effects that are shown in FTIR spectra by the increase in the intensity of the absorption band at 1072 cm(-1) attributed to the vibration of C-H in plane deformation of aromatic ring. The influence of the monomer and the supporting electrolyte concentration as well as the sweep rate on the polymerization conditions in the case of the composites based on the PEK oligomers and CNs were also investigated.
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PMID:Electropolymerization of N-ethylcarbazole on single walled carbon nanotubes-cyclic voltammetry, raman and FTIR studies. 1990 15

An efficient C-C bond formation reaction assisted by a fluoride ion has been identified for N,N'-diphenyl-1,4-phenylenediimine with the compounds having an active methylene group. The reaction follows the typical Michael addition fashion and proceeds to completion within 1 h at 70 degrees C in acetonitrile in the presence of tetrabutylammonium fluoride (TBAF), while the same reaction failed to proceed in the absence of a fluoride anion. The new finding reported herein also offers an unprecedented method for a direct functionalization of polyaniline backbone with versatile functional alkyl groups.
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PMID:A serendipitous C-C bond formation reaction between Michael donors and diiminoquinoid ring assisted by quaternary ammonium fluoride. 1992 99


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