HCN + OH→CN + H2O反应理论研究

The reaction path of the reaction HCN + OH→ CN + H2O was traced with Fukui's theory of intrinsic reaction coordinate by using ab initio MO method (at UMP4/6-31G** level) with gradient technique. On this basis, the dynamics properties along the reaction path was investigated by reaction path Hamiltonian theory. The rate constants of this reaction at different temperatures were calculated by conventional and variational transition state theory with tunneling correction. The theoretically calculated rate constants are in good agreement with experimental results, this shows that the title reaction is an one step, direct reaction.     

Kinetic study of the reaction H2O2+H→H2O+OH by ab initio and density functional theory calculations

Theoretical investigations on the kinetics of the elementary reaction H₂O₂+H→H₂O+OH were performed using the transition state theory (TST). Ab initio (MP2//CASSCF) and density functional theory (B3LYP) methods were used with large basis set to predict the kinetic parameters; the classical barrier height and the pre-exponential factor. The ZPE and BSSE corrected value of the classical barrier height was predicted to be 4.1 kcal mol⁻¹ for MP2//CASSCF and 4.3 kcal mol⁻¹ for B3LYP calculations. The experimental value fitted from Arrhenius expressions ranges from 3.6 to 3.9 kcal mol⁻¹. Thermal rate constants of the title reaction, based on the ab initio and DFT calculations, was evaluated for temperature ranging from 200 to 2500 K assuming a direct reaction mechanism. The modeled ab initio-TST and DFT–TST rate constants calculated without tunneling were found to be in reasonable agreement with the observed ones indicating that the contribution of the tunneling effect to the reaction was predicted to be unimportant at ambient temperature.     

Hydrothermal synthesis, crystal structure and characterization of [Zn(H2O)4]2 [H2As6V15O42(H2O)]·2H2O

The compound [Zn(H₂O)₄]₂[H₂As₆V₁₅O₄₂(H₂O)]·2H₂O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å³, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H₂As₆V₁₅O₄₂(H₂O)]⁴⁻ anions and [Zn(H₂O)₄]²⁺ cations linked through hydrogen bonds into a network. The [H₂As₆V₁₅O₄₂(H₂O)]⁶⁻ cluster consists of 15 VO₅ square pyramids linked by three As₂O₅ handle-like units.     

Quantum chemical study of the hydrogen-bonded HXeOH–H2O complex

A combined MP2 and DFT/B3LYP study of the HXeOH–H₂O complex is presented. These computational methods have been used to extract information on the structural, energetical and vibrational properties of the complex. Additionally, we have applied anharmonic vibrational calculations based on the MP2-computed intermolecular potential energy surface. Large perturbations both on the subunit structures and their fundamental vibrational modes are found upon complexation. Large changes of anharmonicity of the HXeOH subunit reflects the perturbation of the molecule's electronic structure. The computed BSSE-corrected interaction energies are −40.23 and −38.94 kJ mol⁻¹ at the CCSD(T)//MP2 and CCSD(T)//B3LYP levels of theory, respectively. The estimated deformation energy contribution to the interaction energy is about 5%, which is very large compared with classical hydrogen-bonded complexes. The topological analysis of the Electron Localization Function (ELF) was applied to study further the hydrogen-bonded interaction between the two complex partners. The obtained interaction pattern suggests that the interaction between HXeOH and H₂O is a typical hydrogen bond interaction driven mainly by electrostatic interactions.     

The overtone spectra of H2O,D2O and mixtures of H2O in D2O ice

The overtones of the stretching vibration of OH and OD were measured in solid solutions of H₂O in D₂O over a wide range of concentration and temperatures. The observed frequencies and the overall shape of the spectra were related to excitations of single OH or OD bonds (bound excitations) and those involving neighboring OH bonds extending over the crystal (non-bound excitations). The observed large anharmonicity of the bound state is interpreted as due to a low lying barrier in the double minimum potential curve for the hydrogen motion.     

A quantum-mechanical study of the lone-pairs in H2O and H2S

It is shown from SCF-MO studies using localised orbitals that the angles between the lone-pairs in H₂O and H₂S are 115° and 127°, in agreement with the qualitative predictions of the Sidgwick-Powell theory.     

Theoretical study on the reaction pathways of HFCO + H2O

For the reaction of methanoyl fluoride with water, both optimized structures and vibrational wavenumbers of reaction intermediates, transition structures and product complexes were calculated and characterized with theory at the MP2/6-311++G(d,p) level. Including a catalytic path and concerted and stepwise hydrolysis paths, possible reaction mechanisms were also investigated. The catalytic reaction of HFCO yielding HF and CO has the smallest activation barrier, 29.6 kcal/mol, whereas for the concerted hydrolysis 33.0 kcal/mol is required to overcome the barrier to form transoid HCOOH + HF, which is less than for the stepwise counterpart, 42.0 kcal/mol.     

Dipole moment derivatives of H2O and H2S

The dipole and quadrupole derivatives of H₂O and H₂S are calculated analytically, using the coupled Hartree—Fock method first proposed by Gerratt and Mills. The greater efficiency, of this method allows SCF wave functions very, close to the Hartree—Fock limit to be used. Agreement, with experimental data is good.     

Characterisation by rotational spectroscopy of a hydrogen-bonded dimer formed between H2O and HCN

The rotational spectra in the vibrational ground states of (H₂O, HC¹⁴N) and (H₂O, HC¹⁵N) have been assigned in the frequency range 6–19 GHz. Values of rotational constants (B_O, C_O) and centrifugal distortion constants (Δ_J, Δ_JK) have been determined for both species, while the ¹⁴N-nuclear quadrupole coupling constants x_aa and x_bb have been established for the first. Observations concerning additional hyperfine structure arising from H,H nuclear spin-nuclear spin coupling in the H₂O subunit suggest that (H₂O,HCN) has a pair of equivalent protons and is effectively planar in the zero-point state. Observed spectroscopic constants are consistent only with the arrangement H₂O…HCN, with r(O…C) = 3.1387 Å.     

气相中 H2O2与 N2O反应机理的探讨

采用RHF/AM1方法研究了H     

Radioluminescence of H2O and D2O ice spectral characteristics

The spectra of the radiofluorescence RF, afterglow AG and the thermoluminescence TL of H₂O and D₂O ice are reported. The RF spectrum of D₂O exhibits two bands, whereas for H₂O only one of these is seen. The spectrum of TL is different from that of RF and AG. It is argued that if any of these spectra are due to de-excitation of the triplet state of water it is that of the TL. This spectrum is peaked at 335 ± 3 nm and has a width of 46 nm.     

Structural and spectroscopic properties of Hexamethylenetetramine cobalt(II) complex: [Co(NCS)2(hmt)2(H2O)2][Co(NCS)2(H2O)4] (H2O)

Synthesis, structure, spectroscopy and thermal properties of complex [Co(NCS)₂(hmt)₂(H₂O)₂][Co(NCS)₂(H₂O)₄] (H₂O) (I), assembled by hexamethylenetetramine and octahedral Co(II) metal ions, are reported. Crystal data for I: F_w 387.34, a=9.020(8), b=12.887(9), c=7.95(1) Å, =96.73(4), β=115.36(5), γ=94.16(4)°, V=820(1) Å³, Z=2, space group=P−1, T=173 K, λ(Mo-K)=0.71070 Å, ρ_calc=1.718567 g cm⁻³, μ=17.44 cm⁻¹, R=0.088, R_w=0.148. An interesting two-dimensional network is assembled via hydrogen bonds through coordinated and free water molecules. The d–d transition energy levels of Co(II) ion are determined by UV–vis spectroscopy and calculated by ligand field theory. The calculated results agree well with experiment ones.     

Theoretical study on germylenoid H2GeFBeF

The germylenoid H₂GeFBeF was studied by using the DFT B3LYP and QCISD methods in gas phase and in benzene, diethylether, tetrahydrofuran, acetone, and dimethyl sulphoxide solvents. Geometry optimization calculations indicated that H₂GeFBeF has three equilibrium configurations, in which the p-complex structure is the lowest in energy and is the most stable structure. The solvent effect on the geometries, energies, and isomerization reactions were discussed. For the stablest structure, the infrared spectrum was simulated.     

TDDFT Study on Excited-State Hydrogen Bonding of 2'-Deoxyguano-sine in H2O Solution

The mono and dihydrated complexes of 2'-deoxyguanosine have been used to elucidate the importance of the 2'-hydroxy group in the hydration. Density functional theory and time-dependent density functional theory methods were performed to investigate the ground-and excited-state hydrogen bonding properties of 2'-deoxyguanosine-water (2'-dG-W) and 2'-deoxyguanosine-2water (2'-dG-2W). Infrared spectra, geometric optimizations, frontier molecular orbitals and Mulliken charges have also been studied. The results demonstrated that the excited-state intramolecular hydrogen bonding dynamics of complexes 2'-dG-W and 2'-dG-2W behaves differently upon photoexcitation, while their intermolecular hydro-gen bonding dynamics behaves similarly. Moreover, the significant weakening of the inter-molecular hydrogen bond O4···H1?N1 and the formation of the new strong hydrogen bond O4···H3?N2 in the 2'-dG-2W upon photoexcitation were due to the geometric structure bending of guanine and the rigidity of related molecules. In addition, the charge transfer properties were theoretically investigated by analysis of molecular orbital.     

Thermal decomposition mechanisms of MgCl2·6H2O and MgCl2·H2O

The thermal decomposition mechanisms and the intermediate morphology of MgCl₂·6H₂O and MgCl₂·H₂O were studied using integrated thermal analysis, X-ray diffraction, scanning electron microscope and chemical analysis. The results showed that there were six steps in the thermal decomposition of MgCl₂·6H₂O: producing MgCl₂·4H₂O at 69 °C, MgCl₂·2H₂O at 129 °C, MgCl₂·nH₂O (1 ≤ n ≤ 2) and MgOHCl at 167 °C, the conversion of MgCl₂·nH₂O (1 ≤ n ≤ 2) to Mg(OH)Cl·0.3H₂O by simultaneous dehydration and hydrolysis at 203 °C, the dehydration of Mg(OH)Cl·0.3H₂O to MgOHCl at 235 °C, and finally the direct conversion of MgOHCl to the cylindrical particles of MgO at 415 °C. To restrain the sample hydrolysis and to obtain MgCl₂·H₂O, MgCl₂·6H₂O was first calcined in HCl atmosphere until 203 °C when MgCl₂·H₂O was obtained; HCl gas was then turned off and the calcination process continued, producing Mg₃Cl₂(OH)₄·2H₂O calcined at 203 °C, Mg₃(OH)₄Cl₂ at 220 °C and MgO at 360 °C. The temperature of producing MgO from calcination of MgCl₂·H₂O was lower (360 °C) than that from MgCl₂·6H₂O (415 °C) because of its more reactive intermediate products: the irregular shape and tiny needle-like Mg₃Cl₂(OH)₄·2H₂O particles and the uneven surface porous Mg₃(OH)₄Cl₂ particles. The MgO particles obtained at 360 °C had a flake structure.     

NMR study of water reorientation in molybdic acids: MoO3 · 2H2O and yellow MoO3 · H2O

Proton NMR relaxation times (T₂, T₁, T_1?) are reported for powder samples of MoO₃ · 2H₂O and yellow MoO₃ · H₂O in the temperature range 150–325 K and at 20 and 60 MHz. No translation of hydrogen atoms is detected but the spin-lattice relaxation behavior indicates reorientation of H₂O molecules. The waters coordinated to Mo atoms undergo 180° flips (about their C₂ axes) with similar motional parameters in both compounds. The interlayer waters in MoO₃ · 2H₂O undergo 180° flips with different parameters. An assumed Arrhenius-type temperature dependence of correlation times leads to preexponential factors which are “anomalously” low. The possible involvement of temperature-dependent activation barriers is discussed.     

Heat capacity and thermodynamic functions of MnBr2 · 4H2O and MnCl2 · 4H2O

The heat capacities of MnBr₂ · 4H₂O and MnCl₂ · 4H₂O have been experimentally determined from 10 to 300 K. The smoothed heat capacity and the thermodynamic functions (H°_TH°₀) andS°_T are reported for the two compounds over the temperature range 10 to 300 K. The error in these data is thought to be less than 1%. A subtle heat capacity anomaly was observed in MnCl₂ · 4H₂O over the temperature range 52 to 90 K. The entropy associated with the anomaly is of the order 0.4 J/mole K.     

Stabilisation of heterobimetallic networks by crown ethers and hydrogen-bonding in [Ni(H2O)6][Cu3Cl8(H2O)2] · (15-crown-5)2 · 2H2O: Structure and magnetism

[Ni(H₂O)₆][Cu₃Cl₈(H₂O)₂] · (15-crown-5)₂ · 2H₂O can be conveniently prepared by the interaction of NiCl₂ · 6H₂O, CuCl₂ · 2H₂O and 15-crown-5 in water. The X-ray crystal structure reveals an ionic complex involved in a hydrogen-bonded two dimensional network with the [Ni(H₂O)₆]²⁺ and [Cu₃Cl₈(H₂O)₂]²⁻ ions sandwiched between the 15-crown-5 macrocycles. The magnetic susceptibility data (4–300 K) and magnetisation isotherms (2–5.5 K; 0–5 T) are best interpreted in terms of intra-trimer ferromagnetic coupling within the [Cu₃Cl₈(H₂O)₂]²⁻ moieties, with J ∼ 6 cm⁻¹, and antiferromagnetic coupling between the trimers, the latter mediated by H-bonding pathways. Comparisons are made to other reported quaternary ammonium salts of [Cu₃Cl₈]²⁻ and [Cu₃Cl₁₂]⁶⁻, most of which display structures that involve close stacking of such Cu(II) trimers, rather than being of the present isolated, albeit H-bonded, types.     

Determination of ab initio force constants of F2O and H2O

Ab initio SCF calculations at the 4-31G level were performed to obtain the potential surface of the ground states of F₂O and H₂O. The 19-parameter quartic force field and the spectroscopic constants ω_i and x_ij were obtained.     

The dehydration of ZnSO4·7H2O and NiSO4·6H2O

Using differential scanning calorimetry (DSC) in combination with effluent analysis, differential thermal analysis (DTA), thermogravimetric analysis (TG) and X-ray analysis, the dehydration of ZnSO₄·7H₂O and NiSO₄·6H₂O was investigated and a few transition enthalpies were measured. The dehydration of both compounds showed a great analogy. For NiSO₄·6H₂O the α—β phase transition was studied.The dehydration scheme of both hydrates can be given as follows: