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1.
Blackmond DG 《Angewandte Chemie (International ed. in English)》2005,44(28):4302-4320
Reaction progress kinetic analysis to obtain a comprehensive picture of complex catalytic reaction behavior is described. This methodology employs in situ measurements and simple manipulations to construct a series of graphical rate equations that enable analysis of the reaction to be accomplished from a minimal number of experiments. Such an analysis helps to describe the driving forces of a reaction and may be used to help distinguish between different proposed mechanistic models. This Review describes the procedure for undertaking such analysis for any new reaction under study. 相似文献
2.
Two stable 1,3-propanedial tautomers and three their anions have been studied theoretically at MP2 and DFT levels of theory. The energies, structural parameters, ionization potentials, and vibration frequencies have been calculated at the two theoretical levels in order to compare the accuracy of the methods used. The ionization potential of the end form of 1,3-propanedial enol form was estimated to be 752 kJ mol?1; the first and second potentials of the diketo form of 1,3-propanedial are 661 and 1239 kJ mol?1, respectively. 相似文献
3.
Kimel" B. G. Tumanov V. V. Faustov V. I. Promyslov V. M. Egorov M. P. Nefedov O. M. 《Russian Chemical Bulletin》2002,51(8):1568-1574
Reactions of a number of germylenes and dimethylsilylene with a phosphaalkene, 2,2-bis(trimethylsilyl)-1-phenyl-1-phosphaethene (1), were studied. The reaction of short-lived dimethylgermylene with 1 produced a phosphagermirane 3 (the first representative of a new class of heterocyclic compounds). Compound 3 was characterized in solution by 1H, 13C, 31P, and 29Si NMR spectroscopy. Subsequent reaction of 3 with dimethylgermylene results in 2,2,3,3-tetramethyl-4,4-bis(trimethylsilyl)-1-phenyl-2,3-digerma-1-phosphacyclobutane 4, which has not been reported so far. In order to rationalize different reactivities of germylenes towards alkenes and phosphaalkenes, the addition products of GeH2 to ethylene and phosphaethene (HP=CH2) were studied using the G2 computational scheme and DFT PBE technique. The adducts of GeMe2 (GeCl2) with HP=CH2 and of GeMe2 with PhP=C(SiH3)2 were also calculated by the DFT PBE method. According to calculations, the exothermicity, DE, of cycloaddition of GeH2 and GeMe2 to the phosphaalkenes HP=CH2 and PhP=C(SiH3)2 (43.5—39.7 kcal mol–1) is nearly twice as high as the exothermicity of cycloaddition of these germylenes to ethylene. In addition to the minimum corresponding to the three-membered cycle, a number of minima corresponding to quite stable donor-acceptor complexes in which the Ge atom is coordinated by the lone electron pair of the P atom in the phosphaalkene molecule were located on the potential energy surface of the germylene—phosphaalkene system. The complexation energy of the complex of GeH2 (GeMe2) with phosphaethene is 25.0 (16.9) kcal mol–1. For GeCl2, the exothermicity of cycloaddition to HP=CH2 decreases to 7.6 kcal mol–1 and the complexation energy decreases to 8.2 kcal mol–1. 相似文献
4.
Electrochemical reduction of a number of chelate complexes of transition metals (Chel)2M or (Chel)2MXY (M=Co, Rh, Ir, or Ni; Chel are anions of dmgH (dmg is dimethylglyoxime), (3,5-di-tert-butyl-4-hydroxyphenyl)mgH (mg is methylglyoxime),N-aryl-3-methoxysalicylaldoxime,N-aryl-3-methyl-2-thiocarboxamidopyridine, or 2-acetylindan-1,3-dione; X=Y=py, Ph3P, or H2O or X=Cl and Y=Ph3P) in MeCN or DMF was studied using the cyclic voltammetry and rotating disk electrode techniques. Under the action of BunBr, some electrochemically generated anions [(Chel)2M]− enter into the rather fast alkylation reactions (apparently, at the metal atom) to form (Chel)2M—Alk. The geometries of four model neutral and anionic cobalt complexes were calculated using the semiempirical ZINDO/1 method.
According to calculations, the transformation of the neutral complex (Chel)2M into the anion [(Chel)2M]− leads to a change in the configuration from square-planar to square-pyramidal or from tetrahedral to disphenoid. The effects
of steric hindrances, the HOMO energies, and the charge of the metal atom in the anionic complexes on the alkylation reactions
at the metal atom are discussed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 71–77, January, 1999. 相似文献
5.
The structure of the peroxyacetic acid (PAA) molecule and its conformational mobility under rotation about the peroxide bond was studied by ab initio and density functional methods. The free rotation is hindered by the trans-barrier of height 22.3 kJ mol–1. The equilibrium molecular structure of AcOOH (C
s symmetry) is a result of intramolecular hydrogen bond. The high energy of hydrogen bonding (46 kJ mol–1 according to natural bonding orbital analysis) hampers formation of intermolecular associates of AcOOH in the gas and liquid phases. The standard enthalpies of formation for AcOOH (–353.2 kJ mol–1) and products of radical decomposition of the peroxide — AcO· (–190.2 kJ mol–1) and AcOO· (–153.4 kJ mol–1) — were determined by the G2 and G2(MP2) composite methods. The O—H and O—O bonds in the PAA molecule (bond energies are 417.8 and 202.3 kJ mol–1, respectively) are much stronger than in alkyl hydroperoxide molecules. This provides an explanation for substantial contribution of non-radical channels of the decomposition of peroxyacetic acid. The electron density distribution and gas-phase acidity of PAA were determined. The transition states of the ethylene and cyclohexene epoxidation reactions were located (E
a = 71.7 and 50.9 kJ mol–1 respectively). 相似文献
6.
Selmeczi K Michel C Milet A Gautier-Luneau I Philouze C Pierre JL Schnieders D Rompel A Belle C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(32):9093-9106
Dinuclear zinc(II) complexes [Zn(2)(bpmp)(mu-OH)](ClO(4))(2) (1) and [Zn(2)(bpmp)(H(2)O)(2)](ClO(4))(3) (2) (H-BPMP=2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenol) have been synthesized, structurally characterized, and pH-driven changes in metal coordination observed. The transesterification reaction of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) in the presence of the two complexes was studied both in a water/DMSO (70:30) mixture and in DMSO. Complex 2 was not reactive whereas for 1 considerable rate enhancement of the spontaneous hydrolysis reaction was observed. A detailed mechanistic investigation by kinetic studies, spectroscopic measurements ((1)H, (31)P NMR spectroscopy), and ESI-MS analysis in conjunction with ab initio calculations was performed on 1. Based on these results, two medium-dependent mechanisms are presented and an unusual bridging phosphate intermediate is proposed for the process in DMSO. 相似文献
7.
Ignatov S. K. Sennikov P. G. Chuprov L. A. Razuvaev A. G. 《Russian Chemical Bulletin》2003,52(4):837-845
The energies and thermodynamic parameters of elementary steps in the proposed mechanism of silicon tetrafluoride hydrolysis in the gas phase were calculated by the ab initio quantum-chemical method (MP4//MP2/6-311G(2d,2p)) and the density functional theory (B3LYP/6-311G(2d,2p)). The proposed mechanism of gas-phase hydrolysis involves the formation of mono- and dihydroxy derivatives, hexafluorodisiloxane (SiF3OSiF3), and linear and cyclic siloxane polymers with the chain length from three to six Si—O and difluorosilanone units. According to the calculations, all reactions considered are endothermic and are characterized by positive Gibbs free energies. The initial hydrolysis steps can be presented with a high accuracy by two parallel processes: formation of trifluorohydroxysilane (SiF3OH) and SiF3OSiF3. These are the most thermodynamically favorable among all reaction channels. The transition states of these elementary steps were found and their kinetic parameters were estimated (G
= 132 and 147 kJ mol–1, respectively). The calculation results were verified using FTIR spectroscopy of a mixture of gas-phase SiF4 and water vapor. The comparison of the theoretical (absolute) intensities of bands in the IR spectra and integral absorption coefficients in the experimental IR spectrum made it possible to calculate the equilibrium concentrations of the reactants and equilibrium constants of elementary steps of formation of SiF3OH and SiF3OSiF3, which agree with the theoretical values. The role of different derivatives in deep hydrolysis and possibilities of experimental detection of particular intermediates in the gas phase were discussed. 相似文献
8.
The molecular structure and conformational mobility of methyl and tert-butyl esters of peracetic acid AcOOR (R = Me (1), But (2)) were studied by the ab initio MP4(SDQ)//MP2(FC)/6-31G(d,p) method and density functional B3LYP/6-31G(d,p) approach. The B3LYP calculated equilibrium conformations of the molecules are characterized by the C-O-O-C torsion angles of 93.6° (1) and 117.0° (2). Structural features of the molecules under study and a distortion of tetrahedral bond configuration at the Cα atom were explained using the natural bonding orbital approach. The standard enthalpies of formation of AcOOMe (−328.5 kJ mol−1) and AcOOBut (−440.4 kJ mol−1) were determined using the G2 and G2(MP2) computational schemes and the isodesmic reaction approach. The transition state of AcOOMe decomposition into AcOOH and formaldehyde was calculated (E
a = 122.8 kJ mol−1). The thermal effects of homolytic decomposition of the peroxy esters following a concerted mechanism (Me· + CO2 + ·OR) and simple homolysis of the peroxide bond (AcO· + ·OR) were found to be 97.5±0.3 and 155.1±0.3 kJ mol−1, respectively. At temperatures below 400 K, the most probable decomposition mechanism of peroxy esters 1 and 2 involves simple homolysis of the O-O bond.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2021–2027, October, 2004. 相似文献
9.
A. A. Birukov V. I. Faustov M. P. Egorov O. M. Nefedov 《Russian Chemical Bulletin》2005,54(9):2003-2012
The formation and decomposition pathways of germiranes (germacyclopropanes), i.e., products of reactions of the GeH2 and GeMe2 germylenes with ethylene, tetramethylethylene, buta-1,2,3-triene, and tetramethylbuta-1,2,3-triene, were studied using the
density functional approach (PBE/TZ2P approximation). The thermodynamic stabilities of the structures under consideration
were evaluated by calculating the Gibbs free energies under normal conditions (ΔG°298). Addition of germylenes to the C=C bond can proceed as a single-step process without a barrier or involve the formation
of a π-complex (the barrier to this process is lower than the sum of the energies of isolated reactants). Stability of the
germiranes formed is determined by their stability to retrodecomposition into the initial germylene and olefin and to the
three-membered ring opening followed by simultaneous 1,2-migration of the substituent at the Ge atom and formation of the
secondary germylene. Alkyl substituents can efficiently block the opening of the three-membered ring and transformation of
the cyclic structure into the secondary germylene, simultaneously decreasing the germirane stability to retrodecomposition.
Decomposition into germylene and olefin under normal conditions is thermally favorable for hexamethylgermirane (ΔG°298 = −5.7 kcal mol−1), being thermally forbidden for the other germiranes studied in this work (Δ G°298 > 0). The activation energy (E
a) for the germirane ring opening depends on the substituents at the germanium atom, namely, E
a ≤ 10 kcal mol−1 for unsubstituted germiranes and E
a > 30 kcal mol−1 for methyl-substituted germiranes. Taking the experimentally isolated germirane as an example, it was shown how the introduction
of substituents and modification of the carbon skeleton make it possible to stabilize the germacyclopropane system.
Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1943–1951, September, 2005. 相似文献
10.
The stability constants of acetylcholinium, carbamoylcholinium, and cholinium diiodochlorides and diiodobromides in chloroform solutions were determined and the kinetics of disproportionation of these systems in 1 : 9 CHCl3—MeOH (MeCN) mixtures were studied by UV spectroscopy. A possible mechanism of mutual transformations of the polyhalides is proposed and an interrelation between the nature of the iodine-coordinating solvent and the extent of reversibility of the process is established. The electronic structures and relative stabilities of acetylcholinium iodohalides and charge-transfer complexes S·XI2
– and S·I2 (S = MeOH, MeCN, CHCl3; X = Cl, Br, I) were studied by ab initio RHF and MP2(full) methods in the HW+(3d) and 6-31G++(d,p) basis sets. It was found that all the solvents studied favor the decomposition of the iodohalide anions to liberate molecular iodine; however, disproportionation of I2 is possible only for the S·I2 complexes with a high extent of charge transfer. 相似文献
11.
The mechanisms for ClO+NO and its reverse reactions were investigated by means of ab initio molecular orbital and statistical theory calculations. The species involved were optimized at the B3LYP/6-311 +G(3df) level, and their energies were refined at the CCSD(T)/6-311+ G(3df)//B3LYP/6-311 + G(3df) level. Five isomers and the transition states among them were located. The relative stability of these isomers is ClNO2 > cis-ClONO > trans-ClONO > cis-OClNO>trans-OClNO. The heats of formation of the three most-stable isomers were predicted using isodesmic reactions by different methods. The predicted bimolecular reaction rate constant shows that, below 100 atm, the formation of Cl+NO2 is dominant and pressure-independent. The total rate constant can be expressed as: k(ClO+NO)= 1.43 x 10(-9)T(-083)exp(92/ T) cm3 molecule(-1)s(-1) in the temperature range of 200-1000 K, in close agreement with experimental data. For the reverse reaction, Cl+NO2-->ClNO2 and ClONO (cis and trans isomers), the sum of the predicted rate constants for the formation of the three isomers and their relative yields also reproduce the experimental data well. The predicted total third-order rate constants in the temperature range of 200-1000 K can be represented by: k0(He) = 4.89 x 10(-6)T(-5.85) exp(-796/T) cm6 molecule(-1)s(-1) and k0(N2) =5.72 x 10(-15)T(-5.80) exp(-814/T) cm6 molecule(-1)s(-1). The predicted high- and low-pressure limit decomposition rates of CINO2 in Ar in the temperature range 400-1500 K can be expressed, respectively, by: k-(ClNO2) = 7.25 x 10(19)T(-1.89) exp(-16875/T) s(-1) and kd(ClNO2) = 2.51 x 10(38)T(-6.8) exp(-18409/T) cm3 molecule(-1) s(-1). The value of k0(ClNO2) is also in reasonable agreement with available experimental data. 相似文献
12.
Barluenga J Diéguez A Rodríguez F Fañanás FJ Sordo T Campomanes P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(19):5735-5741
The [W(CO)5]-catalyzed cycloisomerization reaction of 1,1-disubstituted 4-pentyn-1-ol derivatives has been studied from both, an experimental and theoretical point of view. Three different catalytic systems have been evaluated {preformed [(thf)W(CO)5], [W(CO)6]/excess Et3N, and [W(CO)6]/2 mol % Et3N]. We have found that the reaction proceeds to give the formal endo- or exo-cycloisomerization products depending on the amount of Et3N used and on the substitution along the alkyl chain of the starting alkynol. The theoretical study allowed us to find the mechanisms of the reactions which explain the formation of the formal endo- or exo-cycloisomerization products. 相似文献
13.
The potential-energy surface for the reaction of ClO with NO2 has been constructed at the CCSD(T)/6-311+G(3df)//B3LYP/6-311+G(3df) level of theory. Six ClNO3 isomers are located; these are ClONO2, pc-ClOONO, pt-ClOONO, OClNO2, pt-OClONO, pc-OClONO, with predicted energies relative to the reactants of -25.6, -0.5, 1.0, 1.9, 12.2 and 13.6 kcal mol-1, and heats of formation at 0 K of 7.8, 32.9, 34.4, 35.5, 45.6 and 47.0 kcal mol-1, respectively. Isomerizations among them are also discussed. The rate constants for the low-energy pathways have been computed by statistical theory calculations. For the association reaction producing exclusively ClONO2, the predicted low- and high-pressure-limit rate constants in N2 for the temperature range of 200-600 K can be represented by: (N2)=3.19 x 10-17 T-5.54 exp(-384 K/T) cm6 molecule-2 s-1 and =3.33 x 10-7 T-1.48 exp(-18 K/T) cm3 molecule-1 s-1. The predicted low- and high-pressure-limit rate constants for the decomposition of ClONO2 in N2 at 200-600 K can be expressed, respectively, by =6.08 x 1013 T-6.54 exp(-13813 K/T) cm3 molecule-1 s-1 and =4.59 x 1023 T-2.43 exp(-13437 K/T) s-1. The predicted values compare satisfactorily with available experimental data. The reverse Cl+NO3 reaction was found to be independent of the pressure, giving exclusively ClO+NO2; the predicted rate constant can be expressed as k(Cl+NO3)=1.19 x 10-9 T-0.60 exp(58 K/T) cm3 molecule-1 s-1.. 相似文献
14.
Binod Raj Giri Krishna Prasad Shrestha Tam V.-T. Mai Fabian Mauss Lam K. Huynh 《国际化学动力学杂志》2023,55(1):3-14
Amino (NH2) radicals play a central role in the pyrolysis and oxidation of ammonia. Several reports in the literature highlight the importance of the reactions of NH2 radicals with fuel in NH3-dual-fuel combustion. Therefore, we investigated the reactions of NH2 radicals with methanol (CH3OH) and ethanol (C2H5OH) theoretically. We explored the various reaction pathways by exploiting CCSD(T)/cc-pV(T, Q)Z//M06-2X/aug-cc-pVTZ level of theory. The reaction proceeds via complex formation at the entrance and exit channels in an overall exothermic process. We used canonical transition state theory to obtain the high-pressure limiting rate coefficients for various channels over the temperature range of 300–2000 K. We discerned the role of various channels in the potential energy surface (PES) of NH2 + CH3OH/C2H5OH reactions. For both reactions, the hydrogen abstraction pathway at the OH-site of alcohols plays a minor role in the entire T-range investigated. By including the title reactions into an extensive kinetic model, we demonstrated that the reaction of NH2 radicals with alcohols plays a paramount role in accurately predicting the low-temperature oxidation kinetics of NH3-alcohols dual fuel systems (e.g., shortening the ignition delay time). On the contrary, these reactions have negligible importance for high-temperature oxidation kinetics of NH3-alcohol blends (e.g., not affecting the laminar flame speed). In addition, we calculated the rate coefficients for NH2 + CH4 = CH3 + NH3 reaction that are in excellent agreement with the experimental data. 相似文献
15.
Dachs A Pla-Quintana A Parella T Solà M Roglans A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(51):14493-14507
N-tosyl-linked open-chain yne-ene-yne enediynes 1 and 2 and yne-yne-ene enediynes 3 and 4 have been satisfactorily synthesised. The [2+2+2] cycloaddition process catalysed by the Wilkinson catalyst [RhCl(PPh(3))(3)] was tested with the above-mentioned substrates resulting in the production of high yields of the cycloadducts. Enediynes 1 and 2 gave standard [2+2+2] cycloaddition reactions whereas enediynes 3 and 4 suffered β-hydride elimination followed by reductive elimination of the Wilkinson catalyst to give cycloadducts, which are isomers of those that would be obtained by standard [2+2+2] cycloaddition reactions. The different reactivities of these two types of enediyne have been rationalised by density functional theory calculations. 相似文献
16.
Jacobsson M Oxgaard J Abrahamsson CO Norrby PO Goddard WA Ellervik U 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(13):3954-3960
The mechanism for the acid-mediated substitution of a phenolic hydroxyl group with a sulfur nucleophile has been investigated by a combination of experimental and theoretical methods. We conclude that the mechanism is distinctively different in nonpolar solvents (i.e., toluene) compared with polar solvents. The cationic mechanism, proposed for the reaction in polar solvents, is not feasible and the reaction instead proceeds through a multistep mechanism in which the acid (pTsOH) mediates the proton shuffling. From DFT calculations, we found a rate-determining transition state with protonation of the hydroxyl group to generate free water and a tight ion pair between a cationic protonated naphthalene species and a tosylate anion. Kinetic experiments support this mechanism and show that, at moderate concentrations, the reaction is first order with respect to 2-naphthol, n-propanethiol, and p-toluenesulfonic acid (pTsOH). Experimentally determined activation parameters are similar to the calculated values (Delta H exp not equal =105+/-9, Delta H calcd not equal =118 kJ mol(-1); Delta G exp not equal =112+/-18, Delta G calcd not equal =142 kJ mol(-1)). 相似文献
17.
O'Neill M. A. A. Beezer A. E. Morris A. C. Urakami K. Willson R. J. Connor J. A. 《Journal of Thermal Analysis and Calorimetry》2003,73(2):709-714
Several recent publications from this laboratory have reported developments in the capacity to calculate thermodynamic and
kinetic parameters, such as rate constant, enthalpy, order of reaction, from isothermal micro-calorimetric data. To date these
developments have all been associated with the calculation of the desired parameters from solution phase reactions. This paper
furthers these developments to a theoretical consideration of solid-state reactions and the calculation of the values for
the rate coefficient, k, the fitting parameters m and n, the total number of joules released over the lifetime of reaction, Q, and hence either the specific enthalpy or the molar enthalpy of reaction, H.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
1-Chlorovinyl p-tolyl sulfoxides were synthesized from ketones and chloromethyl p-tolyl sulfoxide in high yields. Treatment of the sulfoxides with isopropylmagnesium chloride at −78 °C in toluene gave magnesium alkylidene carbenoids (α-chloro alkenylmagnesium chlorides), which were treated with N-lithio arylamines to afford ortho-alkenylated arylamines in moderate yields. The reaction, in some cases, proceeded in a highly stereospecific manner at the carbon bearing the chlorine and the sulfinyl group. The structures of the α-chloro alkenylmagnesium chlorides and the reactivity of the N-lithio meta-substituted anilines were studied at the B3LYP and MP2 levels of theory with the 6-31(+)G* basis set. This reaction offers a quite novel and direct alkenylation of arylamines at the ortho-position of the aromatic ring. 相似文献
19.
Zyubina T. S. Razumov V. F. Brichkin S. B. Anisimov V. M. 《Russian Chemical Bulletin》2002,51(12):2145-2156
The electronic structures and energies of formation of supramolecular complexes of dipyridylethylene with AgNO3 were calculated by the semiempirical AM1/d method, at the Hartree—Fock level, and by the density functional theory (B3LYP/6-31G*). 相似文献
20.
Yu. V. Vishnevskii L. V. Vilkov A. N. Rykov N. M. Karasev Yu. N. Bubnov M. E. Gurskii 《Russian Chemical Bulletin》2005,54(1):99-102
The main structural parameters of the triallylborane molecule having the C
3 symmetry were determined by gas electron diffraction and quantum-chemical calculations at the MP2/6-31G(d,p) and B3LYP/6-31G(d,p) levels. The parameters calculated by the MP2/6-31G(d,p) method are in better agreement with the experimental data than those calculated by the B3LYP/6-31G(d,p) method.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 98–101, January, 2005. 相似文献