15519-25-2Relevant articles and documents
A classical but new kinetic equation for hydride transfer reactions
Zhu, Xiao-Qing,Deng, Fei-Huang,Yang, Jin-Dong,Li, Xiu-Tao,Chen, Qiang,Lei, Nan-Ping,Meng, Fan-Kun,Zhao, Xiao-Peng,Han, Su-Hui,Hao, Er-Jun,Mu, Yuan-Yuan
, p. 6071 - 6089 (2013/09/12)
A classical but new kinetic equation to estimate activation energies of various hydride transfer reactions was developed according to transition state theory using the Morse-type free energy curves of hydride donors to release a hydride anion and hydride acceptors to capture a hydride anion and by which the activation energies of 187 typical hydride self-exchange reactions and more than thirty thousand hydride cross transfer reactions in acetonitrile were safely estimated in this work. Since the development of the kinetic equation is only on the basis of the related chemical bond changes of the hydride transfer reactants, the kinetic equation should be also suitable for proton transfer reactions, hydrogen atom transfer reactions and all the other chemical reactions involved with breaking and formation of chemical bonds. One of the most important contributions of this work is to have achieved the perfect unity of the kinetic equation and thermodynamic equation for hydride transfer reactions. The Royal Society of Chemistry.
Nonconventional versus conventional application of pseudo-first-order kinetics to fundamental organic reactions
Parker, Vernon D.,Hao, Weifang,Li, Zhao,Scow, Russell
experimental part, p. 2 - 12 (2012/03/22)
Three new analysis procedures for pseudo-first-order kinetics are introduced and applied to eight different fundamental organic reactions. The reactions belong to the following classes: nitroalkane proton transfer, formal hydride ion transfers from NADH model compounds, and SN2 reactions of alkyl halides with ionic and neutral nucleophiles. The three methods consist of (1) half-life dependence of kapp, (2) sequential linear pseudo-first-order correlation, and (3) revised instantaneous rate constant analysis. Each of the three procedures is capable of distinguishing between one- and multistep mechanisms, and the combination of the three procedures provides a powerful strategy for differentiating between the two mechanistic possibilities. The data from the eight reactions chosen as examples clearly show how the procedures work in practice.
Thermodynamic diagnosis of the properties and mechanism of dihydropyridine-type compounds as hydride source in acetonitrile with molecule id card
Zhu, Xiao-Qing,Tan, Yue,Cao, Chao-Tun
scheme or table, p. 2058 - 2075 (2010/07/16)
A series of 45 dihydropyridine-type organic compounds as hydride source were designed and synthesized. The thermodynamic driving forces (defined as enthalpy changes or redox potentials in this work) of the dihydropyridines to release hydride anions, hydrogen atoms (hydrogen for short), and electrons in acetonitrile,the thermodynamic driving forces of the radical cations of the dihydropyridines to release protons and hydrogens in acetonitrile, and the thermodynamic driving forces of the neutral pyridine-type radicals of the dihydropyridines to release electron in acetonitrile were determined by using titration calorimetry and electrochemical methods. The rates and activation parameters of hydride transfer from the dihydropyridines to acridinium perclorate, a well-known hydride acceptor, were determined by using UV-vis absorption spectroscopy technique. The relationship between the thermodynamic driving forces and kinetic rate of the hydride transfer was examined. Thermodynamic characteristic graph (TCG) of the dihydropyridines as an efficient Molecule ID Card was introduced. The TCG can be used to quantitatively diagnose or predict the characteristic chemical properties of the dihydropyridines and their various reaction intermediates. The mechanism of hydride transfer from the dihydropyridines to acridinium perclorate was diagnosed and elucidated by using the determined thermodynamic parameters and the activation parameters..
Investigations of the fragmentation pathways of benzylpyridinium ions under ESI/MS conditions
Zins, Emilie-Laure,Rondeau, David,Karoyan, Philippe,Fosse, Celine,Rochut, Sophie,Pepe, Claude
experimental part, p. 1668 - 1675 (2010/07/08)
Benzylpyridinium ions are often used as 'thermometer ions' in order to evaluate the internal energy distribution of the ions formed in sources of mass spectrometers. However, the detailed fragmentation pathways of these parent ions were not well establish
Reactions of charged substrates. 4. The gas-phase dissociation of (4-substituted benzyl) dimethylsulfoniums and -pyridiniums
Buckley, Neil,Maltby, David,Burlingame, Alma L.,Oppenheimer, Norman J.
, p. 2753 - 2762 (2007/10/03)
The relative rates for the gas-phase dissociation RX- → R- + X° of five (4-Y-substituted benzyl)-dimethysulfoniums (Y = MeO, Me, H, Cl, and NO2) and 24 (4-Y-substituted benzyl)-3′-Z-pyridiniums (complete series for Z = CN, Cl, CONH2, and H, and 4-methoxy- and 4-nitrobenzyls for Z = F and CH3CO) were measured using liquid secondary ion mass spectrometry. The Hammett plot (vs δΔG° or σ-) is linear for the sulfoniums, but plots for the four pyridinium series have a drastic break between the 4-Cl and 4-NO2 substrates. Bronsted-like plots for the pyridiniums show a strong leaving group effect only for 4-nitrobenzyls. An analysis of these linear free energy relations with supporting evidence from semiempirical computations suggests that collisionally activated pyridinium substrates dissociate by two pathways, direct dissociation and through an ion-neutral complex intermediate. Comparison of these results with results for the solution reactions of some of these compounds shows that the mechanism is different in the gas and solution phases. Sufficient experimental data are not available to assign a mechanism for dissociation to the sulfonium series, but computational results show characteristics of a direct dissociative mechanism.
Energetic Comparison between Photoinduced Electron-Transfer Reactions from NADH Model Compounds to Organic and Inorganic Oxidants and Hydride-Transfer Reactions from NADH Model Compounds to p-Benzoquinone Derivatives
Fukuzumi, Shunichi,Koumitsu, Shintaro,Hironaka, Katsuhiko,Tanaka, Toshio
, p. 305 - 316 (2007/10/02)
Kinetics studies on photoinduced electron-transfer reactions from dihydropyridine compounds (PyH2) as being NADH model compounds to organic and inorganic oxidants and hydride-transfer reactions from PyH2 to p-benzoquinone derivatives (Q) in the absence and presence of Mg2+ ion are reported by determining over 150 rate constants.These results, combined with the values of Gibbs energy change of the photoinduced electron-transfer reactions as well as those of each step of the hydride-transfer reactions as being the e--H+-e- sequence, which are determined independently, revealed that the rate constants of the photoinduced electron-transfer reactions obey the Rehm-Weller-Gibbs energy relationship and that the activation barrier of the hydride-transfer reactions from PyH2 to Q is dependent solely on the Gibbs energy changes of the initial electron transfer from PyH2 to Q and the following proton transfer from PyH2.+ to Q.- and thus independent of the Gibbs energy change of the final electron transfer from PyH. to QH..The retarding effect of Mg2+ ion observed on the photoinduced electron transfer and hydride-transfer reactions of PyH2 is ascribed to the positive shifts of the redox potentials of the ground and excited states of PyH2 due to the complex formation with Mg2+ ion.
BIOMIMETIC REDUCTION WITH NON WATER-SENSITIVE NADH MODELS
Cazin, J.,Dupas, G.,Bourguignon, J.,Queguiner, G.
, p. 2375 - 2378 (2007/10/02)
Two NADH models were synthesized which are considerably less water-sensitive than classical-1,4 dihydronicotinamide derivatives such as N-benzyl-1,4 dihydronicotinamide (BNAH): these two models are reactive and more stable in the presence of water than previously reported models.
The kinetics and primary isotope effect for reduction of acridinium ions by a NAD(P)H "model"; facts and fallacy
Laar, A. van,Ramesdonk, H. J. van,Verhoeven, J. W.
, p. 157 - 163 (2007/10/02)
A kinetic study of the reduction of the 10-methyl-9-phenylacridinium ions (ACPh+) by 1-benzyl-1,4-dihydronicotinamide (PyH2) is presented.The primary kinetic isotope effect (kH/kD=4.5) of this reaction equals the product isotope partitioning observed upon reduction with mono C-4 deuterated 1-benzyl-1,4-dihydronicotinamide (PyHD).Furthermore, the rate constant for the reduction decreases upon increasing the solvent polarity.This behaviour contrasts with that reported for the reduction of the 10-methylacridinium ion (AcH+)where acceleration due to increased solvent polarity and significant discrepancies between the kinetic isotope effect and the product isotope partitioning have been observed.Reinvestigation of the latter process by means of kinetic measurements and via a competition experiment, involving reduction with equal amounts of PyH2 and the dideuterated species (PyD2), shows that the kinetic data and especially the kinetic isotope effect data are easily subject to experimental error.Thus it is shown that an intolerable inaccuracy is introduced if the value of kH/kD is determined by comparing the rate of reduction with that of PyHD rather than by comparing those of PyH2 and PyD2.Furthermore, the kinetic data in protic solvent for AcH+, but not for AcPh+, are found to be disturbed by a reversible side reaction.This reaction is thought to involve formation of a covalent adduct by attack of PyH2 at the electrophilic C-9 position of AcH+.The less electrophilic nature of this position in AcPh+ prevents such adduct formation and leads to uncomplicated kinetic behaviour in all the solvent systems investigated.
A Direct Method based on Hydride Exchange for Determining the Redox Potentials of 1,4-Dihydropyridines Related Structurally to Nicotine Adenine Dinucleotide (NADH)
Kellogg, Richard M.,Piepers, Oscar
, p. 402 - 404 (2007/10/02)
The relative two-electron redox potentials of N-substituted 1,4-dihydropyridines related to NADH can be determined by a direct method in which the equilibrium composition of a 1,4-dihydropyridine-pyridinium salt mixture is determined by 1H n.m.r. spectroscopy.
Kinetics and Mechanisms of Nucleophilic Displacements with Heterocycles as Leaving Groups. 1. 1-Benzyl-2,4,6-triphenylpyridinium
Katritzky, Alan R.,Musumarra, Giuseppe,Sakizadeh, Kumars,Misic-Vukovic, Milica
, p. 3820 - 3823 (2007/10/02)
Second-order rate constants demonstrate the importance of ionic strength for the reactions of 1-benzyl-2,4,6-triphenylpyridinium cation with anionic but not neutral nucleophiles.The logarithms of the rate constants decrease linearly with the solvent dielectric constants for iodide and with ET for piperidine.
