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1.
SUBALA MONDAL SUMON RAY ANIMESH CHATTOPADHYAY DEBABRATA NANDI ROSHNI SARKAR ALAK KUMAR GHOSH 《国际化学动力学杂志》2014,46(10):587-596
The kinetics of the interactions between three sulfur‐containing ligands, thioglycolic acid, 2‐thiouracil, glutathione, and the title complex, have been studied spectrophotometrically in aqueous medium as a function of the concentrations of the ligands, temperature, and pH at constant ionic strength. The reactions follow a two‐step process in which the first step is ligand‐dependent and the second step is ligand‐independent chelation. Rate constants (k1 ~10?3 s?1 and k2 ~10?5 s?1) and activation parameters (for thioglycolic acid: ΔH1≠ = 22.4 ± 3.0 kJ mol?1, ΔS1≠ = ?220 ± 11 J K?1 mol?1, ΔH2≠ = 38.5 ± 1.3 kJ mol?1, ΔS2≠ = ?204 ± 4 J K?1 mol?1; for 2‐thiouracil: ΔH1≠ = 42.2 ± 2.0 kJ mol?1, ΔS1≠ = ?169 ± 6 J K?1 mol?1, ΔH2≠ = 66.1 ± 0.5 kJ mol?1, ΔS2≠ = ?124 ± 2 J K?1 mol?1; for glutathione: ΔH1≠ = 47.2 ± 1.7 kJ mol?1, ΔS1≠ = ?155 ± 5 J K?1mol?1, ΔH2≠ = 73.5 ± 1.1 kJ mol?1, ΔS2≠ = ?105 ± 3 J K?1 mol?1) were calculated. Based on the kinetic and activation parameters, an associative interchange mechanism is proposed for the interaction processes. The products of the reactions have been characterized from IR and ESI mass spectroscopic analysis. A rate law involving the outer sphere association complex formation has been established as 相似文献
2.
The dynamic behavior of the N,N,N′,N′‐tetramethylethylenediamine (tmeda) ligand has been studied in solid lithium‐fluorenide(tmeda) ( 3 ) and lithium‐benzo[b]fluorenide(tmeda) ( 4 ) using CP/MAS solid‐state 13C‐ and 15N‐NMR spectroscopy. It is shown that, in the ground state, the tmeda ligand is oriented parallel to the long molecular axis of the fluorenide and benzo[b]fluorenide systems. At low temperature (<250 K), the 13C‐NMR spectrum exhibits two MeN signals. A dynamic process, assigned to a 180° rotation of the five‐membered metallacycle (π‐flip), leads at elevated temperatures to coalescence of these signals. Line‐shape calculations yield ΔH?=42.7 kJ mol?1, ΔS?=?5.3 J mol?1 K?1, and =44.3 kJ mol?1 for 3 , and ΔH?=36.8 kJ mol?1, ΔS?=?17.7 J mol?1 K?1, and =42.1 kJ mol?1 for 4 , respectively. A second dynamic process, assigned to ring inversion of the tmeda ligand, was detected from the temperature dependence of T1ρ, the 13C spin‐lattice relaxation time in the rotating frame, and led to ΔH?=24.8 kJ mol?1, ΔS?=?49.2 J mol?1 K?1, and =39.5 kJ mol?1 for 3 , and ΔH?=18.2 kJ mol?1, ΔS?=?65.3 J mol?1 K?1, and =37.7 kJ mol?1 for 4 , respectively. For (D12)‐ 3 , the rotation of the CD3 groups has also been studied, and a barrier Ea of 14.1 kJ mol?1 was found. 相似文献
3.
This paper will compare the mechanism and kinetics of living carbocationic polymerization of isobutylene (IB) and styrene (St), initiated by the 2-chloro-2,4,4-trimethyl-pentane (TMPCl) / TiCl4) system in 60/40 (v/v) methylcyclohexane / methyl chloride mixed solvent at −80 and −75 °C. The rate of initiation was found to be first order in TiCl4 in both systems. While initiation is instantaneous in IB polymerization at [TiCl4]0 ⩾ [TMPCl]0, it is slow in St polymerization. Kinetic derivation showed that initiating efficiency is dependent on [M] in this latter system, which was also demonstrated experimentally. The apparent initiation rate constant was determined from initiator consumption rate data and was found to be ki,app = 1.39 l2/mol2sec. The rate of St consumption measured using a real time fibre-optic mid-FTIR monitoring technique compared well with gravimetric data and was found to be closer to first order in TiCl4 at [TiCl4]0 < [TMPCl]0. However, the rate followed a close to second order in TiCl4 at [TiCl4]0 ⩾ [TMPCl]0. The mechanistic model proposed earlier for living carbocationic IB polymerization, which yielded good agreement with experimental data, seems to apply to carbocationic St polymerization as well. This model reconciles the discrepancy between rate constants published for carbocationic IB and St polymerizations, and accounts for shifting TiCl4 orders. However, independent investigations are necessary to verify the proposed mechanistic model. Optimized conditions led to living carbocationic St polymerization producing high molecular weight PS with 100% initiating efficiency. 相似文献
4.
Pd-catalyzed double carbomethoxylation of the Diels-Alder adduct of cyclo-pentadiene and maleic anhydride yielded the methyl norbornane-2,3-endo-5, 6-exo-tetracarboxylate ( 4 ) which was transformed in three steps into 2,3,5,6-tetramethyl-idenenorbornane ( 1 ). The cycloaddition of tetracyanoethylene (TCNE) to 1 giving the corresponding monoadduct 7 was 364 times faster (toluene, 25°) than the addition of TCNE to 7 yielding the bis-adduct 9 . Similar reactivity trends were observed for the additions of TCNE to the less reactive 2,3,5,6-tetramethylidene-7-oxanorbornane ( 2 ). The following second order rate constants (toluene, 25°) and activation parameters were obtained for: 1 + TCNE → 7 : k1 = (255 + 5) 10?4 mol?1 · s?1, ΔH≠ = (12.2 ± 0.5) kcal/mol, ΔS≠ = (?24.8 ± 1.6) eu.; 7 + TCNE → 9 , k2 = (0.7 ± 0.02) 10?4 mol?1 · s?1, ΔH≠ = (14.1 ± 1.0) kcal/mol, ΔS≠ = ( ?30 ± 3.5) eu.; 2 + TCNE → 8 : k1 = (1.5 ± 0.03) 10?4 mol?1 · s?1, ΔH≠ = (14.8 ± 0.7) kcal/mol, ΔS≠ = (?26.4 ± 2.3) eu.; 8 + TCNE → 10 ; k2 = (0.004 ± 0.0002) 10?4 mol?1 · s?1, ΔH≠ = (17 ± 1.5) kcal/mol, ΔS≠ = (?30 ± 4) eu. The possible origins of the relatively large rate ratios k1/k2 are discussed briefly. 相似文献
5.
Abstract The effect of anion concentration on the apparent rate constant of polymerization kA p of isobutylene (IB) induced by the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl4 initiating system using the CH2Cl2/nC6H14 (60/40 v/v) solvent system at ?40 and ?80°C was studied by the use of nBu4NCl. Computer simulation has shown that kA p decreases several orders of magnitude upon the addition of even a very small amount of common anion TiCl?- 5 to the charge. The rate of change is reduced in the concentration range of experimental interest. It was concluded that the decrease of kA p with increasing TiCl ?- 5 concentration is mainly due to the decreasing contribution of propagation by free ions. The contribution (%) of propagation by free ions to the apparent rate of propagation was calculated. 相似文献
6.
The [2.2.2]hericene ( 6 ), a bicyclo[2.2.2]octane bearing three exocyclic s-cis-butadiene units has been prepared in eight steps from coumalic acid and maleic anhydride. The hexaene 6 adds successively three mol-equiv. of strong dienophiles such as ethylenetetracarbonitrile (TCE) and dimethyl acetylenedicarboxylate (DMAD) giving the corresponding monoadducts 17 and 20 (k1), bis-adducts 18 and 21 (k2) and tris-adducts 19 and 22 (k3), respectively. The rate constant ratio k1/k2 is small as in the case of the cycloadditions of 2,3,5,6-tetramethylidene-bicyclo [2.2.2]octane ( 3 ) giving the corresponding monoadducts 23 and 27 (k1) and bis-adducts 25 and 29 (k2) with TCE and DMAD, respectively. Constrastingly, the rate constant ratio k2/k3 is relatively large as the rate constant ratio k1/k2 of the Diels-Alder additions for 5,6,7,8-tetramethylidenebicyclo [2.2.2]oct-2-ene ( 4 ) giving the corresponding monoadducts 24 and 28 (k1) and bis-adducts 26 and 30 (k2). The following second-order rate constants (toluene, 25°) and activation parameters were obtained for the TCE additions: 3 +TCE→ 23 : k1 = 0.591±0.012 mol?1·l·s?1, ΔH≠=10.6±0.4 kcal/mol, and ΔS≠ = ?24.0±1.4 cal/mol·K (e.u.); 23 +TCE→ 25 : k2=0.034±0.0010 mol?1·l·s?1, ΔH≠ = 10.6±0.6 kcal/mol, and ΔS≠ = ?29.7±2.0 e.u.; 4 +TCE→ 26 : k1 = 0.172±0.035 mol?1·l·s?1, ΔH≠ 11.3±0.8 kcal/mol, and ΔS≠ = ?24.0±2.8 e.u.; 24 +TCE→ 26 : k2 = (6.1±0.2)·10?4 mol?1·l·s?1, ΔH≠ = 13.0±0.3 kcal/mol, and ΔS≠ = ?29.5±0.8 e.u.; 6 +TCE→ 17 : k1 = 0.136±0.002 mol?1·l·s?1, ΔH≠ = 11.3±0.2 kcal/mol, and ΔS≠ = ?24.5±0.8 e.u.; 17 +TCE→ 18 : k2 = 0.0156±0.0003 mol?1·l·s?1, ΔH≠ = 10.9±0.5 kcal/mol, and ΔS≠ = ?30.1 ± 1.5 e.u.; 18 +TCE→ 19 : k3=(5±0.2) · 10?5 mol?1 mol?1 ·l·s?1, ΔH≠ = 15±3 kcal/mol, and ΔS≠ = ?28 ± 8 e.u. The following rate constants were evaluated for the DMAD additions (CD2Cl2, 30°): 6 +DMAD→ 20 : k1 = (10±1)·10?4 mol?1 · l·s?1; 20 +DMAD→ 21 : k2 = (6.5±0.1) · 10?4 mol?1 ·l·?1; 21 +DMAD→ 22 : k3 = (1.0±0.1) · 10?4 mol?1 ·l·s?1. The reactions giving the barrelene derivatives 19, 22, 26 and 30 are slower than those leading to adducts that are not barrelenes. The former are estimated less exothermic than the latter. It is proposed that the Diels-Alder reactivity of exocyclic s-cis-butadienes grafted onto bicycle [2.2.1]heptanes and bicyclo [2.2.2]octanes that are modified by remote substitution of the bicyclic skeletons can be affected by changes inthe exothermicity of the cycloadditions, in agreement with the Dimroth and Bell-Evans-Polanyi principle. Force-field calculations (MMPI 1) of 3, 4, 6 and related exocyclic s-cis-butadienes as a moiety of bicyclo [2.2.2]octane suggested single minimum energy hypersurfaces for these systems (eclipsed conformations, planar dienes). Their flexibility decreases with the degree of unsaturation of the bicyclic skeleton. The effect of an endocyclic double bond is larger than that of an exocyclic diene moiety. 相似文献
7.
Shane A. Seabrook Matthew P. Tonge Robert G. Gilbert 《Journal of polymer science. Part A, Polymer chemistry》2005,43(7):1357-1368
Pulsed laser polymerization was used in conjunction with aqueous‐phase size exclusion chromatography with multi‐angle laser light scattering detection to determine the propagation rate coefficient (kp) for the water‐soluble monomer acrylamide. The influence of the monomer concentration was investigated from 0.3 to 2.8 M, and kp decreased with increasing monomer concentration. These data and data for acrylic acid in water were consistent with this decrease being caused by the depletion of the monomer concentration by dimer formation in water. Two photoinitiators, uranyl nitrate and 2,2′‐azobis(2‐amidinopropane) (V‐50), were used; kp was dependent on their concentrations. The concentration dependence of kp was ascribed to a combination of solvent effects arising from association (thermodynamic effects) and changes in the free energy of activation (effects of the solvent on the structure of the reactant and transition state). Arrhenius parameters for kp (M?1 s?1) = 107.2 exp(?13.4 kJ mol?1/RT) and kp (M?1 s?1) = 107.1 exp(?12.9 kJ mol?1/RT) were obtained for 0.002 M uranyl nitrate and V‐50, respectively, with a monomer concentration of 0.32 M. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1357–1368, 2005 相似文献
8.
Refat M. Hassan 《Journal of polymer science. Part A, Polymer chemistry》1993,31(5):1147-1151
The kinetics of decomposition of [Alg · Mn VIO42?] intermediate complex have been investigated spectrophotometrically at a constant ionic strength of 0.5 mol dm?3. The decomposition reaction was found to be first-order in the intermediate concentration. The results showed that the rate of reaction was base-catalyzed. The kinetic parameters have been evaluated and found to be ΔS? = ?103.88±6.18 J mol?1 K?1, ΔH? = 51.61 ± 1.02 kJ mol?1, and ΔG? = 82.57 ± 2.86 kJ mol?1, respectively. A reaction mechanism consistent with the results is discussed. © 1993 John Wiley & Sons, Inc. 相似文献
9.
Khalid S. Khairou 《国际化学动力学杂志》2003,35(2):67-72
The kinetics of decomposition of an [Pect·MnVIO42?] intermediate complex have been investigated spectrophotometrically at various temperatures of 15–30°C and a constant ionic strength of 0.1 mol dm?3. The decomposition reaction was found to be first‐order in the intermediate concentration. The results showed that the rate of reaction was base‐catalyzed. The kinetic parameters have been evaluated and found to be ΔS≠ = ? 190.06 ± 9.84 J mol?1 K?1, ΔH≠ = 19.75 ± 0.57 kJ mol?1, and ΔG≠ = 76.39 ± 3.50 kJ mol?1, respectively. A reaction mechanism consistent with the results is discussed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 67–72, 2003 相似文献
10.
Maik Finze Dr. Jan A. P. Sprenger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(38):9918-9927
The anionic gold(I) complexes [1‐(Ph3PAu)‐closo‐1‐CB11H11]? ( 1 ), [1‐(Ph3PAu)‐closo‐1‐CB9H9]? ( 2 ), and [2‐(Ph3PAu)‐closo‐2‐CB9H9]? ( 3 ) with gold–carbon 2c–2e σ bonds have been prepared from [AuCl(PPh3)] and the respective carba‐closo‐borate dianion. The anions have been isolated as their Cs+ salts and the corresponding [Et4N]+ salts were obtained by salt metathesis reactions. The salt Cs‐ 3 isomerizes in the solid state and in solution at elevated temperatures to Cs‐ 2 with ΔHiso=(?75±5) kJ mol?1 (solid state) and ΔH≠=(118±10) kJ mol?1 (solution). The compounds were characterized by vibrational and multi‐NMR spectroscopies, mass spectrometry, elemental analysis, and differential scanning calorimetry. The crystal structures of [Et4N]‐ 1 , [Et4N]‐ 2 , and [Et4N]‐ 3 were determined. The bonding parameters, NMR chemical shifts, and the isomerization enthalpy of Cs‐ 3 to Cs‐ 2 are compared to theoretical data. 相似文献
11.
The reaction between chromium(VI) and L-ascorbic acid has been studied by spectrophotometry in the presence of aqueous citrate buffers in the pH range 5.69–7.21. The reaction is slowed down by an increase of the ionic strength. At constant ionic strength, manganese(II) ion does not exert any appreciable inhibition effect on the reaction rate. The rate law found is where Kp is the equilibrium constant for protonation of chromate ion and kr is the rate constant for the redox reaction between the active forms of the oxidant (hydrogenchromate ion) and the reductant (L-hydrogenascorbate ion). The activation parameters associated with rate constant kr are Ea = 20.4 ± 0.9 kJ mol?1, ΔH≠ = 17.9 ± 0.9 kJ mol?1, and ΔS≠=?152 ± 3 J K?1 mol?1. The reaction thermodynamic magnitudes associated with equilibrium constant Kp are ΔH0 = 16.5 ± 1.1 kJ mol?1 and ΔS0 = 167 ± 4 J K?1 mol?1. A mechanism in accordance with the experimental data is proposed for the reaction. © 1993 John Wiley & Sons, Inc. 相似文献
12.
Ondrej Kysel Šimon Budzák Miroslav Medveď Pavel Mach 《International journal of quantum chemistry》2008,108(9):1533-1545
Geometry, thermodynamic, and electric properties of the π‐EDA complex between hexamethylbenzene (HMB) and tetracyanoethylene (TCNE) are investigated at the MP2/6‐31G* and, partly, DFT‐D/6‐31G* levels. Solvent effects on the properties are evaluated using the PCM model. Fully optimized HMB–TCNE geometry in gas phase is a stacking complex with an interplanar distance 2.87 × 10?10 m and the corresponding BSSE corrected interaction energy is ?51.3 kJ mol?1. As expected, the interplanar distance is much shorter in comparison with HF and DFT results. However the crystal structures of both (HMB)2–TCNE and HMB–TCNE complexes have interplanar distances somewhat larger (3.18 and 3.28 × 10?10 m, respectively) than our MP2 gas phase value. Our estimate of the distance in CCl4 on the basis of PCM solvent effect study is also larger (3.06–3.16 × 10?10 m). The calculated enthalpy, entropy, Gibbs energy, and equilibrium constant of HMB–TCNE complex formation in gas phase are: ΔH0 = ?61.59 kJ mol?1, ΔS = ?143 J mol?1 K?1, ΔG0 = ?18.97 kJ mol?1, and K = 2,100 dm3 mol?1. Experimental data, however, measured in CCl4 are significantly lower: ΔH0 = ?34 kJ mol?1, ΔS = ?70.4 J mol?1 K?1, ΔG0 = ?13.01 kJ mol?1, and K = 190 dm3 mol?1. The differences are caused by solvation effects which stabilize more the isolated components than the complex. The total solvent destabilization of Gibbs energy of the complex relatively to that of components is equal to 5.9 kJ mol?1 which is very close to our PCM value 6.5 kJ mol?1. MP2/6‐31G* dipole moment and polarizabilities are in reasonable agreement with experiment (3.56 D versus 2.8 D for dipole moment). The difference here is due to solvent effect which enlarges interplanar distance and thus decreases dipole moment value. The MP2/6‐31G* study supplemented by DFT‐D parameterization for enthalpy calculation, and by the PCM approach to include solvent effect seems to be proper tools to elucidate the properties of π‐EDA complexes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
13.
Kinetics of the complex formation of chromium(III) with alanine in aqueous medium has been studied at 45, 50, and 55°C, pH 3.3–4.4, and μ = 1 M (KNO3). Under pseudo first-order conditions the observed rate constant (kobs) was found to follow the rate equation: Values of the rate parameters (kan, k, KIP, and K) were calculated. Activation parameters for anation rate constants, ΔH≠(kan) = 25 ± 1 kJ mol?1, ΔH≠(k) = 91 ± 3 kJ mol?1, and ΔS≠(kan) = ?244 ± 3 JK?1 mol?1, ΔS≠(k) = ?30 ± 10 JK?1 mol?1 are indicative of an (Ia) mechanism for kan and (Id) mechanism for k routes (‥substrate Cr(H2O) is involved in the k route whereas Cr(H2O)5OH2+ is involved in k′ route). Thermodynamic parameters for ion-pair formation constants are found to be ΔH°(KIP) = 12 ± 1 kJ mol?1, ΔH°(K) = ?13 ± 3 kJ mol?1 and ΔS°(KIP) = 47 ± 2 JK?1 mol?1, and ΔS°(K) = 20 ± 9 JK?1 mol?1. 相似文献
14.
Leon A.P. Kane-Maguire Paul D. Mouncher Albrecht Salzer 《Journal of organometallic chemistry》1979,168(2):C42-C44
A stopped-flow investigation of the reversible addition of Ph3P to [(C8H11)Co(C5H5)]+ indicates the rate law, kobs = k1[Ph3P] + k?1. The low Δ2 of 21.0 ± 1.2 kJ mol?1 and the negative ΔS2 of ?114 ± 5 J K?1 mol?1 are consistent with rapid addition to the enyl ligand. The higher Δ2 of 86.2 ± 5.1 kJ mol?1 and the positive ΔS2 of +60 ± 17 J K?1 mol?1are as expected for the reverse dissociation. Preliminary studies show that the related complex [(C7H9)Co(C5H5)]+ is at least 65 times more electrophilic towards Ph3P. 相似文献
15.
A Remarkable Solvent Effect on the Nuclearity of Neutral Titanium(IV)‐Based Helicate Assemblies
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David Michael Weekes Carine Diebold Dr. Pierre Mobian Dr. Clarisse Huguenard Dr. Lionel Allouche Prof. Marc Henry 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(17):5092-5101
The spontaneous self‐assembly of a neutral circular trinuclear TiIV‐based helicate is described through the reaction of titanium(IV) isopropoxide with a rationally designed tetraphenolic ligand. The trimeric ring helicate was obtained after diffusion of n‐pentane into a solution with dichloromethane. The circular helicate has been characterized by using single‐crystal X‐ray diffraction study, 13C CP‐MAS NMR and 1H NMR DOSY solution spectroscopic, and positive electrospray ionization mass‐spectrometric analysis. These analytical data were compared with those obtained from a previously reported double‐stranded helicate that crystallizes in toluene. The trimeric ring was unstable in a pure solution with dichloromethane and transformed into the double‐stranded helicate. Thermodynamic analysis by means of the PACHA software revealed that formation of the double‐stranded helicates was characterized by ΔH(toluene)=?30 kJ mol?1 and ΔS(toluene)=+357 J K?1 mol?1, whereas these values were ΔH(CH2Cl2)=?75 kJ mol?1 and ΔS(CH2Cl2)=?37 J K?1 mol?1 for the ring helicate. The transformation of the ring helicate into the double‐stranded helicate was a strongly endothermic process characterized by ΔH(CH2Cl2)=+127 kJ mol?1 and ΔH(n‐pentane)=+644 kJ mol?1 associated with a large positive entropy change ΔS=+1115 J K?1?mol?1. Consequently, the instability of the ring helicate in pure dichloromethane was attributed to the rather high dielectric constant and dipole moment of dichloromethane relative to n‐pentane. Suggestions for increasing the stability of the ring helicate are given. 相似文献
16.
Peng‐Fei Yan An‐Ru Guo Qiang Liu Yi‐Xian Wu 《Journal of polymer science. Part A, Polymer chemistry》2012,50(16):3383-3392
A simple but effective FeCl3‐based initiating system has been developed to achieve living cationic polymerization of isobutylene (IB) using di(2‐chloro‐2‐propyl) benzene (DCC) or 1‐chlorine‐2,4,4‐trimethylpentane (TMPCl) as initiators in the presence of isopropanol (iPrOH) at ?80 °C for the first time. The polymerization with near 100% of initiation efficiency proceeded rapidly and completed quantitatively within 10 min. Polyisobutylenes (PIBs) with designed number‐average molecular weights (Mn) from 3500 to 21,000 g mol?1, narrow molecular weight distributions (MWD, Mw/Mn ≤ 1.2) and near 100% of tert‐Cl terminal groups could be obtained at appropriate concentrations of iPrOH. Livingness of cationic polymerization of IB was further confirmed by all monomer in technique and incremental monomer addition technique. The kinetic investigation on living cationic polymerization was conducted by real‐time attenuated total reflectance Fourier transform infrared spectroscopy. The apparent constant of rate for propagation (kpA) increased with increasing polymerization temperature and the apparent activation energy (ΔEa) for propagation was determined to be 14.4 kJ mol?1. Furthermore, the triblock copolymers of PS‐b‐PIB‐b‐PS with different chain length of polystyrene (PS) segments could be successfully synthesized via living cationic polymerization with DCC/FeCl3/iPrOH initiating system by sequential monomer addition of IB and styrene at ?80 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
17.
邻苯二胺与5-氯-2-羟基二苯酮、邻香草醛作用合成了一种不对称希夫碱配体C27H21N2O3Cl(H2L)。在正丁醇和甲醇体系中硝酸铀酰与该配体反应合成了一种固体希夫碱配合物[UO2(HL)(NO3)(H2O)]·H2O。通过元素分析、IR、UV、1H NMR、TG-DTG及摩尔电导率分析等手段对合成的配合物进行了表征,用非等温热重法研究了铀(Ⅵ)配合物的热分解反应动力学,推断出第三步热分解的动力学方程为:d α /d t = A · e- E/RT ·3/2[(1- α )-1/3-1]-1,得到了动力学参数E和A。并计算出了活化熵△S¹和活化吉布斯自由能△G¹。 相似文献
18.
Zsanett Gecse István Ilisz Melinda Nonn Nóra Grecsó Ferenc Fülöp Rajalingam Agneeswari Myung Ho Hyun Antal Péter 《Journal of separation science》2013,36(8):1335-1342
The application of a chiral ligand‐exchange column for the direct high‐performance liquid chromatographic enantioseparation of unusual β‐amino acids with a sodium N‐((R)‐2‐hydroxy‐1‐phenylethyl)‐N‐undecylaminoacetate‐Cu(II) complex as chiral selector is reported. The investigated amino acids were isoxazoline‐fused 2‐aminocyclopentanecarboxylic acid analogs. The chromatographic conditions were varied to achieve optimal separation. The effects of temperature were studied at constant mobile phase compositions in the temperature range 5–45°C, and thermodynamic parameters were calculated from plots of lnk or lnα versus 1/T. Δ(ΔH°) ranged from –2.3 to 2.2 kJ/mol, Δ(ΔS°) from –3.0 to 7.8 J mol?1 K?1 and –Δ(ΔG°) from 0.1 to 1.7 kJ/mol, and both enthalpy‐ and entropy‐controlled enantioseparations were observed. The latter was advantageous with regard to the shorter retention and greater selectivity at high temperature. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes. The sequence of elution of the enantiomers was determined in all cases. 相似文献
19.
The kinetics of base hydrolysis of (αβ S)-(o -methoxy benzoato) (tetraethylenepentamine)cobalt(III) obeyed the rate law: kobs = kOH[OH?], in the range 0.05 ? [OH?]T, mol dm?3 ? 1.0, I = 1.0 mol dm?3, and 20.0–40.0°C. At 25°C, kOH = 13.4 ± 0.4 dm3 mol?1 s?1, ΔH≠ = 93 ± 2 kJ mol?1 and ΔS≠ = 90 ± 5 JK?1 mol?1. Several anions of varying charge and basicity, CH3CO2?, SO32?, SO42?, CO32?, C2O42?, CH2(CO2)22?, PO43?, and citrate3? had no effect on the rate while phthalate2?, NTA3?, EDTA4?, and DTPA5? accelerated the process via formation of the reactive ion pairs. The anionic (SDS), cationic (CTAB), and neutral (Triton X-100) micelles, however, retarded the reaction, the effect being in the order SDS> CTAB > Triton X-100. The importance of electrostatic and hydrophobic effects of the micelles on the selective partitioning of the reactants between the micellar and bulk aqueous pseudo-phases which control the rate are discussed. © 1994 John Wiley & Sons, Inc. 相似文献
20.
Radhey M. Naik Abhinav Agarwal Amit K. Verma Shiv Bali S. Yadav Basant Kumar 《国际化学动力学杂志》2009,41(4):215-226
The kinetics and mechanism of Hg2+‐catalyzed substitution of cyanide ion in an octahedral hexacyanoruthenate(II) complex by nitroso‐R‐salt have been studied spectrophotometrically at 525 nm (λmax of the purple‐red–colored complex). The reaction conditions were: temperature = 45.0 ± 0.1°C, pH = 7.00 ± 0.02, and ionic strength (I) = 0.1 M (KCl). The reaction exhibited a first‐order dependence on [nitroso‐R‐salt] and a variable order dependence on [Ru(CN)64?]. The initial rates were obtained from slopes of absorbance versus time plots. The rate of reaction was found to initially increase linearly with [nitroso‐R‐salt], and finally decrease at [nitroso‐R‐salt] = 3.50 × 10?4 M. The effects of variation of pH, ionic strength, concentration of catalyst, and temperature on the reaction rate were also studied and explained in detail. The values of k2 and activation parameters for catalyzed reaction were found to be 7.68 × 10?4 s?1 and Ea = 49.56 ± 0.091 kJ mol?1, ΔH≠ = 46.91 ± 0.036 kJ mol?1, ΔS≠ = ?234.13 ± 1.12 J K?1 mol?1, respectively. These activation parameters along with other experimental observations supported the solvent assisted interchange dissociative (Id) mechanism for the reaction. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 215–226, 2009 相似文献