Proton Transfer Process (proton + transfer_process)

Distribution by Scientific Domains


Selected Abstracts


Dynamic Behavior of an N -Metalated ,-Enaminoimine Complex , Preparation of N -Phosphanylenamine and ,-Enaminoimine Derivatives

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2003
Alexandrine Maraval
Abstract Variable-temperature NMR spectroscopy of the ,-enaminoimine complex 2 showed a dynamic process which was attributed to an internal fluxional aldimido N -zirconated ,-linear/,-bent structure. Such an internal rearrangement has been previously proposed to occur in these systems but never observed. We have prepared a variety of (N -phosphanyl-,-enamino)imine ligands using the hydrozirconation/transmetalation reaction of malonodinitrile compounds RCH(CN)2 (R = H, PPh2). In addition to their potential uses in coordination chemistry, these systems are good tools for the study of intramolecular hydrogen bonding. The X-ray crystal structure of 14 at 180 K shows an unsymmetrical system with the N(H) proton localized on one of the two chelating nitrogen atoms, consistent with the existence in solution of a low barrier proton transfer process with a double-well potential. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]


Theoretical study of the reaction mechanism of proton transfer in glycinamide

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2006
Liqun Zhang
Abstract To investigate the tautomerism of glycinamide that is induced by proton transfer, we present detailed theoretical studies on the reaction mechanism of both the isolated gas phase and H2O-assisted proton transfer process of glycinamide, using density functional theory calculations by means of the B3LYP hybrid functional. Twenty-six geometries, including 10 significant transition states, were optimized, and these geometrical parameters are discussed in detail. The relative order of the activation energy for hydrogen atom transfer of all the conformers has been systematically explored in this essay. For the amido hydrogen atom transfer process, the relative order of the activation energy is: IV < II < III < I, while in the carbonic hydrogen atom transfer process, the relative order is IV > II > III > I. Meanwhile, the most favorable structure for both the amido hydrogen atom transfer and the carbonic hydrogen atom transfer has been found. The involvement of the water molecule not only can stabilize the transition states and the ground states, but can also reduce the activation energy greatly. The superior catalytic effect of H2O has been discussed in detail. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source]


A comprehensive theoretical study on the hydrolysis of carbonyl sulfide in the neutral water

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2008
Chao Deng
Abstract The detailed hydration mechanism of carbonyl sulfide (COS) in the presence of up to five water molecules has been investigated at the level of HF and MP2 with the basis set of 6-311++G(d, p). The nucleophilic addition of water molecule occurs in a concerted way across the CS bond of COS rather than across the CO bond. This preferential reaction mechanism could be rationalized in terms of Fukui functions for the both nucleophilic and electrophilic attacks. The activation barriers, ,H, for the rate-determining steps of one up to five-water hydrolyses of COS across the CS bond are 199.4, 144.4, 123.0, 115.5, and 107.9 kJ/mol in the gas phase, respectively. The most favorable hydrolysis path of COS involves a sort of eight-membered ring transition structure and other two water molecules near to the nonreactive oxygen atom but not involved in the proton transfer, suggesting that the hydrolysis of COS can be significantly mediated by the water molecule(s) and the cooperative effects of the water molecule(s) in the nonreactive region. The catalytic effect of water molecule(s) due to the alleviation of ring strain in the proton transfer process may result from the synergistic effects of rehybridization and charge reorganization from the precoordination complex to the rate-determining transition state structure induced by water molecule. The studies on the effect of temperature on the hydrolysis of COS show that the higher temperature is unfavorable for the hydrolysis of COS. PCM solvation models almost do not modify the calculated energy barriers in a significant way. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source]


Generation of Cationic [Zr-{tert -Butyl Enolate}] Reactive Species: Methyl Abstraction versus Hydride Abstraction

CHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2004
Bing Lian Dr.
Abstract Treatment of the neutral methyl,Zr,enolate [Cp2Zr(Me){O(tBuO)CCMe2}] (1) with one equivalent of B(C6F5)3 or [HNMe2Ph][B(C6F5)4] as a methyl abstractor in THF at 0,°C leads to the selective formation of the free ion pair complex [Cp2Zr(THF){O(tBuO)CCMe2}]+,[anion], (2) (anion=MeB(C6F5)3,, B(C6F5)4,), which is relevant to the controlled polymerization of methacrylates. Cation 2 rapidly decomposes at 20,°C in THF with release of one equivalent of isobutene to form the cationic Zr,carboxylate species [Cp2Zr(THF)(O2CiPr)]+ (3), through a proposed intramolecular proton transfer process from the tert -butoxy group to the enolate. The reaction of 1 with one equivalent of B(C6F5)3 or [HNMe2Ph][B(C6F5)4] in CH2Cl2 leads to the direct, rapid formation of the dimeric ,-isobutyrato,Zr dicationic species [{Cp2Zr[,-(O2CiPr)]}2]2+ (4), which gives 3 upon dissolution in THF. Contrastingly, when [Ph3C][B(C6F5)4] is used to generate the cationic Zr,enolate species from 1 in CD2Cl2, a 15:85 mixture of dicationic complexes 4 and [{Cp2Zr[, -(O2CC(Me)CH2)]}2]2+[B(C6F5)4] (5 -[B(C6F5)4]2) is obtained quantitatively. The formation of 5 is proposed to arise from initial hydride abstraction from a methyl enolate group by Ph3C+, as supported by the parallel production of Ph3CH, and subsequent elimination of methane and isobutene. In addition to standard spectroscopic and analytical characterizations for the isolated complexes 2,5, complexes 4 and 5 have also been structurally characterized by X-ray diffraction studies. [source]


Reversible Photoregulation of the Electrical Conductivity of Spiropyran-Doped Polyaniline for Information Recording and Nondestructive Processing ,

ADVANCED MATERIALS, Issue 7 2004
X. Guo
Reversibly photoswitchable proton transfer processes can occur between a three-state molecular switch based on spiropyran (SP) and the "salt form" of polyaniline (see Figure), both in solution and in the solid state. As a result, the electrical conductivity of the thin-film of SP-doped polyaniline can be photoregulated. [source]