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1.
The energetics of the phenol O–H bond in methanol and the water O–H bond in liquid water were investigated by microsolvation modelling and statistical mechanics Monte Carlo simulations. The microsolvation approach was based on density functional theory calculations. Optimised structures for clusters of phenol and the phenoxy radical with one and two methanol molecules are reported. By analysing the differential solvation of phenol and the phenoxy radical in methanol, we predict that the phenol O–H homolytic bond dissociation enthalpy in solution is 24.3±11 kJ/mol above the gas-phase value. The analysis of the water O–H bond dissociation by microsolvation was based on optimised structures of OH–(H2O)1–6 and –(H2O)1–7 clusters. Microsolvation modelling and statistical mechanics simulations predict that the HO–H bond dissociation enthalpies in the gas phase and in liquid water are very similar. Our results stress the importance of estimating the differences between the solvation enthalpies of the radical species and the parent molecule and the limitations of local models based on microsolvation.Proceedings of the 11th International Congress of Quantum Chemistry satellite meeting in honor of Jean-Louis Rivail 相似文献
2.
The reactivity of TpPtMe(H)(2) (Tp = hydrido-tris(pyrazolyl)borate) was investigated. This complex is remarkably resistant to methane loss; heating it in methanol at 55 degrees C does not lead to either methane or hydrogen loss. When CD(3)OD is used, reversible H/D scrambling of the hydrides and the methyl hydrogens occurs. This reactivity was investigated by density functional theory (DFT) methods at the mPW1k/LANL2DZ+P//mPW1k/LANL2DZ level. It was found that methane loss cannot occur due to the rigidity of the Tp ligand, which does not allow the trans geometry which would be required for the product of methane elimination, TpPtH. The resulting complex is very high in energy, and therefore the loss of methane is unfavorable. On the other hand, H/D scrambling of the methyl ligand is relatively facile. It proceeds through an eta(2-CH)-CH(4) complex, even though methane loss is not observed. The model system, [(NH(3))(3)PtMe(H)(2)](+) was examined to verify that the cause of the observations is the rigidity of the Tp system. The reaction was investigated at a number of levels of DFT. It was concluded that investigations of similar sized systems should be examined at the above level of theory or the mPW1k/SDB-cc-pVDZ//mPW1k/SDD level for improved accuracy of the energetic calculations. 相似文献
3.
Dong Dao-Qing Gao Xing Li Li-Xia Hao Shuang-Hong Wang Zu-Li 《Research on Chemical Intermediates》2018,44(12):7557-7567
Research on Chemical Intermediates - A tetrabutylammonium iodide (TBAI)-catalyzed method for synthesis of 2-sulfolmethyl quinolone has been developed. Using water as solvent, a wide range of... 相似文献
4.
《Journal of organometallic chemistry》1988,346(1):C4-C6
Reaction-solution calorimetric studies involving the complexes Ti[η5-C5(CH3)5]2-(CH3)2, Ti[η5-C5(CH3)5]2(CH3), Ti[η5-C5(CH3)5]2(C6H5), Ti[η5-C5(CH3)5]2Cl2, and Ti[η5-C5(CH3)5]2Cl, have enabled derivation of titaniumcarbon and titaniumchlorine stepwise bond dissociation enthalpies in these species. 相似文献
5.
Milo Netopilík Miloslav Bohdanecký Vladimír Chytrý Karel Ulbrich 《Macromolecular rapid communications》1997,18(2):107-111
Time-dependent phase separation/transition was observed in aqueous solutions of poly(N-isopropylmethacrylamide) in the temperature range 38–42°C. The time before the second phase appears is a function of temperature and may reach up to several hours. 相似文献
6.
Liu G Ping L Li H 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,66(3):643-645
B3LYP/6-311+G** level of theory is used to investigate the C-H...O hydrogen bond formed by chloroform and two conformers of triformylmethane (TFM), i.e. cis-TFM (concerned with C1 configuration) and trans-TFM (concerned with C2 and C3 configurations). Polarized continuum model (PCM) is used to study the solvent (chloroform) effect on this hydrogen bond. The C3 configuration is more stable than the C1 configuration whether the absolute energy or the stabilization energy is concerned. For the C1 and C2 configurations this hydrogen bond is of blue-shifted type both in gas phase and in chloroform solution. For the C3 configuration this hydrogen bond is of red-shifted type in gas phase but turns into blue-shifted type in chloroform solution instead. It's inappropriate to simply designate this hydrogen bond as blue-shifted type or red-shifted type. 相似文献
7.
8.
In this paper, a biocatalytic route is described wherein PPL, lipase from porcine pancreas, in conjunction with water on reaction with different thiophenols and styrene oxides undergo thiolysis with C-S bond formation without the use of any metal catalysts, oxidants, bases, additives or organic solvents towards formation of β-hydroxysulfides in good to excellent yields with high regioselectivity at room temperature. Furthermore, PPL also facilitates thiophenols to undergo hydrothiolation with styrenes or phenylacetylenes in sole water and thus forming linear thioethers or vinylsulfides respectively via C–S bond formation. In addition to the straightforward and atom-efficient protocol, a gram-scale synthesis of β-hydroxysulfide and recyclability for three consecutive cycles without decrease in efficiency of PPL make our biocatalytic protocol for constructing C–S bond highly valuable from both environmental and economic viewpoints than traditional chemical practices. 相似文献
9.
The consensus value for the electron affinity of azide radical is 261 kJ mol−1, anomalously higher than many species that are also made of highly electronegative elements. N3
− has two equivalent resonance structures analogous to NO2
− that has a lower electron affinity. Electronegativity trends rationalize why the electron affinity of N3 is higher than that of P3; however, those of N and N2 are lower than those of P and P2. We suggest the reason for the observed high electron affinity of azide radical is Coulombic stabilization in the ionic triplet
resonance structure, −N=N+=N−. 相似文献
10.
11.
The compounds [C4H8ON(C3H5)2]+[Cu4Cl5]– (I), [C4H8ONH(C3H5)]+[CuBr2]– (II), and [C4H8ONH(C3H5)]+[CuBr1.41Cl0.59]– (III) were prepared for the first time by ac electrochemical synthesis from mono- and di-N-allyl derivatives of morpholinium and copper(I) halides in ethanol solution and structurally characterized. In the structure of I π-complex, the centrosymmetric Cu8Cl10 fragments are associated into layers perpendicular to the b axis. The N,N"-diallylmorpholinium cation functions as a bridge, which coordinates two copper atom of the adjacent inorganic fragments by both allyl groups. The trigonal-pyramidal surrounding of the Cu(I) atom, as well as the distorted tetrahedral coordination sphere of Cu(2), involves three chlorine atoms and the C=C bond, whereas the planar trigonal surrounding of the Cu(3) atom and trigonal-pyramidal surrounding of the Cu(4) atom involve only chlorine atoms. In the isostructural II and III σ-complexes, the edge-shared CuX4 tetrahedra form the infinite copper-halide chains running along the a axis. The inorganic fragments and organic N-allylmorpholinium cations are united into the three-dimensional crystal structures by N–H···X and C–H···X (X = Cl, Br) hydrogen bonds. 相似文献
12.
The structures of several naphthalene derivatives and their35Cl NQR spectra have been investigated. 1,8-Diaminonaphthalene,C
2v
9
-Pna2
1, Z = 8,a (in pm) = 881,b = 1577,c = 1213; 1,8-diaminonaphthalene monodichloroacetate,C
2h
6
-C2/c, Z = 8,a = 2050,b = 584,c = 2333, (in degrees) = 110.1; 1,8-diaminonaphthalene monotrichloroacetate,C
1
1
-P¯1, Z=2,a=1211,b=1062,c=589,=74.8,=80.1,=70.9; 1-aminonaphthalene trichloroacetate,D
2h
15
-Pbca, Z=8,a=2347,b=1289,c=889. The35Cl NQR spectrum of 1,8-diaminonaphthalene monodichloroacetate is a doublet, the frequencies decreasing with increasing temperature from 77 to 217 K at which temperatureT
b the NQR signals bleach out. A35Cl NQR triplet is found for 1,8-diaminonaphthalene monotrichloracetate in the range 77 77K 207 (=T
b
). 1-Amino-naphthalene trichloroacetate shows a35Cl NQR triplet, too, withT
b = 136 K. Characteristic for the intermolecular interactions are hydrogen bonds in the chloroacetic acid salts; each NH3 group forms three hydrogen bonds, and of the two oxygens one is involved in two such bonds, one in one bond. Thereby units of two cations and two anions are formed, and these dirners are connected to strings by hydrogen bonds. Additional van der Waals interactions between the chlorine atoms and the naphthalene ring system are observed. Comparison of the intramolecular bond distances C(i)-C(j) of the C10 naphthalene skeleton for 41 naphthalene derivatives (present data and literature) shows that the bond distances C(i)-C(j)are little influenced by substitution, as is the mean bond length. Shorter and longer distances prove a partial localization of charge at C(1)-C(2), C(3)-C(4), C(5)-C(6), and C(7)-C(8). Regularities within the bond angles and characteristic influences of 1,8-disubstitution on it are discussed. 相似文献
13.
《Chemical physics》1987,118(3):457-466
The gas-phase clustering reactions Cl− (ROH)n−1 + ROH ⇄ Cl− (ROH)n with n ⩽ 11 for ROH = H2O, CH3OH, C2H5OH, i-C3H7OH, n-C3H7OH, and t-C4H9OH were measured using a high-pressure mass spectrometer. It seems likely that for CH3OH and C2H5OH, six ligands complete the shell structure and that ligands with n ⩾ 7 belong to the outer shell. The bond energies D(ROH---Cl−) increase in the order H2O < CH3OH < C2H5OH < i-C3H7OH < t-C4H9OH < n-C3H7OH. The observed strong bond of n-C3H7OH---Cl− may be due to the fact that both the acidic hydrogen atoms in the −OH and terminal −CH3 of n-C3H7OH interact with Cl− with the most favorable configuration. For Cl− switching reactions, Cl− (H2O)n + (ROH)n ⇄ Cl− (ROH)n + (H2O)n, the ΔG0n values converge to the values of free energies of transfer of Cl− from water to ROH solvent ( = ΔG0n with n → ∞) with n ≈ 7. The observed convergence of ΔG0n is due to compensation of changes in enthalpy and entropy, i.e. both ΔH0n and TΔS0n show increasing divergence from the values of enthalpies and entropies of transfer of Cl− from water to ROH solvent, respectively, with n = 1 → 7. This is due to the stronger interactions of ROH with Cl− than that of H2O in the inner shell of Cl− (ROH)n at the expense of the less favorable entropy changes (less freedom of motion for ligands in the inner shell). 相似文献
14.
《Journal of organometallic chemistry》1986,315(2):187-199
The heats of reaction of HMo(CO)3C5H5 with CX4 (X = Cl, Br) producing XMo(CO)3C5H5 have been measured by solution calorimetry and are −31.8±0.9 and −34.4±2.0 kcal/mole, respectively. The heats of reaction of NaMo(CO)3C5H5 with I2 and CH3I producing IMo(CO)3C5H5 and H3CMo(CO)3C5H5 are −32.3± 1.3 and −7.7± 0.3 kcal/mole. Oxidation with Br2CCl4 yielding Br3Mo(CO)2C5H5 was measured for the following complexes: (C5H5(CO)3Mo)2, (−92.0±1.0 kcal/mole), BrMo(CO)3C5H5 (−24.9± 2.0 kcal/mole) and HMo(CO)3C5H5 (−60.7± 2.0 kcal/mole). These and other data are used to calculate the Mo–X bond strength for X = H, Cl, Br, I, and CH3. These bond strength estimates are compared to those reported for X2Mo(C5H5)2. Iodination of H3CMo(CO)3C5H5, reported in the literature to yield CH3I and IMo(CO)3C5H5, actually produces CH3C(O)I and I3Mo(CO)2C5H5. 相似文献
15.
Quantum mechanical calculations at the MP4 (SDQ) level using the BP86‐optimized geometries were carried out to investigate the energies and reaction mechanism for the propene (CH3 C1H CH$^{\mathrm{2}}_{\mathrm{2}}$) insertion reaction into the Rh H bond, using the cis‐HRh(CO)(PH3)2 compound as a model catalytic species. Since the reaction may occur on the branched carbon 1 or in the normal carbon 2 , which leads to branched and normal Rh(alkyl) compounds, respectively, we investigated these two mechanisms. The results show that the insertion in the branched carbon has an activation energy of 16.2 kcal/mol, and the activation energy for the reaction to take place at the normal carbon is 14.3 kcal/mol. These activation energies, together with the calculated relative energy of the metal–alkyl compounds formed after the insertion considering these two pathways, were used to access the regioselectivity on this reaction. We found a ratio of normal‐ and iso‐products, n:iso, of (96:4), which is in excellent agreement with the experimental regioselectity of (95:5). © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 42–51, 2000 相似文献
16.
用光谱法研究了异戊二烯顺-1,4聚合催化体系Ln(napb)3-Al(i-C4H9)3-Al2(C2H5)3Cl3中稀土离子的价态.结果表明,在上述催化体系中,镨,钕,钆,铒部以三价形式存在,这说明上述稀土化合物催化活性的不同,不是因为价态有所差异.对不同条件下含Nd(naph)3的催化剂溶液的光谱及聚合活性研究结果表明,催化活性与Nd+3的特征吸收强度有关,吸收强度愈强,活性愈高.提高铝/钕克分子比及延长催化剂陈化时间,都导致特征吸收强度及催化活性的增大. 相似文献
17.
Dissociation and ionization competing processes for H2+ in intense laser field: which one is larger?
Competition between dissociation and ionization of H(2)(+) in intense laser field has been investigated by using an accurate three-dimensional time-dependent wavepacket approach. The disagreement between the experiment and the former one-dimensional theory has been resolved. In a comparison of the calculated results with the available experimental data, a good agreement is reached, not only for the relative probabilities between dissociation and ionization but also for the two-peak structures and the peak energy locations for these two processes. 相似文献
18.
Machado Poliana A. L. Cavalcanti Marcello H. S. Silva Fábio A. B. de Almeida Eduardo T. Cardoso Marcus V. C. Mesquita Anderson F. Lemes Nelson H. T. Virtuoso Luciano S. 《Journal of solution chemistry》2022,51(3):320-344
Journal of Solution Chemistry - Liquid–liquid equilibrium (LLE) data and phase diagrams for new aqueous two-phase systems (ATPSs) containing 1-butyl-3-methylimidazolium chloride... 相似文献
19.
Olga A. Efremova Yuri V. Mironov Hans-Jürgen Pietzsch Holger Stephan Christiane Perrin Vladimir E. Fedorov 《Journal of Cluster Science》2009,20(1):77-81
Abstract A new cubane-type cluster complex Re4Te4Cl4(C4H4N3)4 · 2DMF has been synthesized by reaction of Re4Te4Cl8(TeCl2)4 with 2-aminopyrazine C4H5N3 in DMF. The crystal structure of compound has been solved by X-ray single crystal diffraction method. Crystal data for Re4Te4Cl4(C4N3H4)4 · 2DMF: a = 22.8718(16) ?, b = 8.5936(7) ?, c = 20.5720(17) ?, β
o = 106.493(2), V = 3877.1(5) ?3, R
1 = 0.0466, R
w(F
2) = 0.1191. In the complex bidentate aminopyrazine ligands are coordinated in two different types, namely, two of four aminopyrazine
ligands bind to a single rhenium atom, and each of two other ligands is coordinated as bridge between two rhenium atoms.
Graphical Abstract A new cubane-type cluster complex Re4Te4Cl4(C4H4N3)4 · 2DMF with two coordination modes of bidentate aminopyrazine ligands has been synthesized and structurally characterized.
相似文献
20.
Trajectory calculations run on global potential energy surfaces have shown that the topology of the entrance channel has strong implications on the dynamics of the title reactions. This may explain why huge differences are observed between the rate constants calculated from global dynamical methods and those obtained from local methods that employ the same potential energy surfaces but ignore such topological details. Local dynamics approaches such as transition state-based theories should then be used with caution for fine-tuning potential energy surfaces, especially for fast reactions with polyatomic species since the key statistical assumptions of the theory may not be valid for all degrees of freedom. 相似文献