共查询到20条相似文献,搜索用时 31 毫秒
1.
Ruizhou Zhang Zhenguo Li Xiaohong Li Xianzhou Zhang 《Frontiers of Chemistry in China》2011,6(2):69-75
Theoretical study of several O-nitrosyl carboxylate compounds have been performed using quantum computational ab initio RHF
and density functional B3LYP and B3PW91 methods with 6-31G** basis set. Geometries obtained from DFT calculations were used
to perform the natural bond orbital (NBO) analysis. It is noted that weakness in the O3-N2 bond is due to $
n_{O_1 } \to \sigma _{O_3 - N_2 }^*
$
n_{O_1 } \to \sigma _{O_3 - N_2 }^*
delocalization and is responsible for the longer O3-N2 bond lengths in O-nitrosyl carboxylate compounds. It is also noted that decreased occupancy of the localized $
\sigma _{O_3 - N_2 }
$
\sigma _{O_3 - N_2 }
orbital in the idealized Lewis structure, or increased occupancy of $
\sigma _{O_3 - N_2 }^*
$
\sigma _{O_3 - N_2 }^*
of the non-Lewis orbital, and their subsequent impact on molecular stability and geometry (bond lengths) are related with
the resulting p character of the corresponding sulfur natural hybrid orbital (NHO) of $
\sigma _{O_3 - N_2 }
$
\sigma _{O_3 - N_2 }
bond orbital. In addition, the charge transfer energy decreases with the increase of the Hammett constants of subsitutent
groups. 相似文献
2.
A. N. Novikov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(9):1520-1525
Heat capacities of solutions of alkali metal iodides (MeI) in N-methylpyrrolidone (MP)-water mixed solvent were measured over
the range of compositions. The influence of the composition of the mixed solvent on the heat capacity of MeI-MP-H2O ternary systems is discussed. Standard partial molar heat capacities $
\bar C_{p_2 }^o
$
\bar C_{p_2 }^o
(MeI) in the MP-water mixed solvent at 298.15 K are calculated. 相似文献
3.
Triple molybdate NaCoCr(MoO4)3, a phase of variable composition Na2MoO4-CoMoO4-Cr2(MoO4)3 (0 ≤ x ≤ 0.5) having nasicon structure (space group R
$
\bar 3
$
\bar 3
c), and triple molybdate NaCo3Cr(MoO4)5 crystallizing in triclinic space group P
$
\bar 1
$
\bar 1
were synthesized in the subsolidus region of the Na2MoO4-CoMoO4-Cr2(MoO4)3 ternary salt system. Crystal parameters were calculated for the newly synthesized molybdates and phases. The vibration spectra
of Na1 − x
Co1 − x
Cr1 + x
(MoO4)3 and electrophysical properties were studied. Upon Na + Co → Cr(III) substitution, chromium cations are distributed to cobalt
sites and additional vacancies are generated in the sodium sublattice. 相似文献
4.
G. D. Tsyrenova S. F. Solodovnikov N. N. Pavlova Z. A. Solodovnikova 《Russian Journal of Inorganic Chemistry》2010,55(5):771-779
Subsolidus phase relations in the Cs2MoO4-MMoO4-Zr(MoO4)2 (M = Mn, Zn) ternary systems were determined, and two groups of new isostructural triple molybdates were synthesized: Cs2MZr(MoO4)4 and Cs2MZr2(MoO4)6 (M = Mn, Mg, Co, Zn). Cs2MnZr2(MoO4)6 and Cs2MnZr(MoO4)4 crystals were grown by spontaneous flux crystallization and used in structure solution for both groups of compounds. The
Cs2MnZr2(MoO4)6 structure (a =13.4322(2) ?, c = 12.2016(3) ?, group R3, Z = 3, R = 0.0367) is a new structure type characterized by a mixed three-dimensional framework built of corner-sharing MoO4 tetrahedra and (M, Zr)O6 octahedra where large channels are occupied by cesium cations. Cs2MnZr2(MoO4)4 (a =5.3890(1) ?, c = 8.0685(3) ?, space group P
$
\bar 3
$
\bar 3
m1, Z = 0.5, R = 0.0247) has the layered glaserite-like KAl(MoO4)2 type structure, where Al3+ octahedral positions are randomly occupied by a 0.5M2+ + 0.5Zr4+ mixture. 相似文献
5.
Shi-You Li Pei-Hua Ma Xiao-Ling Cui Qi-Du Ren Fa-Qiang Li 《Journal of Chemical Sciences》2008,120(2):289-292
Thermal decomposition of LiPF6 and LiBC4O8 (lithium bis(oxalate)borate, abbreviated as LiBOB) were studied using TG (thermogravimetry)-DTG (derivative thermogravimetry) method with
different heating rate β of 5, 10, 20 and 40°C min−1 or at different constant temperature θ
C
(109·80, 118·79, 148·41, 176·86°C for LiPF6 and 278·51, 298·13, 317·65, 336·13 for LiBOB). From the non-isothermal kinetics we calculate that is 1·01, n
LiBOB is 1·04, is 91907·61 J/mol, and E
LiBOB is 205179·88 J/mol; from the isothermal kinetics we calculate that n for both LiPF6 and LiBOB are 1, ELiPF6 is 91907·61 J/mol, E
LiBOB is 205179·88 J/mol, is 16·89 s−1, and lnALiBOB is 31·96 s−1. The results obtained from the two ways have minor differences and can validate each other. 相似文献
6.
A. N. Novikov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(8):1337-1339
The heat capacity and density of solutions of sodium and potassium perchlorates in N-methylpyrrolidone (MP) at 298.15 K were
studied by calorimetry and densimetry. The standard partial molar heat capacities $
\bar C_{p2}^ \circ
$
\bar C_{p2}^ \circ
and volumes $
\bar V_2^ \circ
$
\bar V_2^ \circ
of NaClO4 and KClO4 in MP were calculated. The standard heat capacities $
\bar C_{pi}^ \circ
$
\bar C_{pi}^ \circ
and volumes $
\bar V_i^ \circ
$
\bar V_i^ \circ
of the perchlorate ion in an MP solution at 298.15 K were determined. The results are discussed with allowance for the specifics
of solvation in the solutions of the salts under study. The coordination number of the ClO4− ion in an MP solution at 298.15 K was calculated. 相似文献
7.
The volta potential difference method at 298.15 K was used to determine the real primary medium effect for magnesium, calcium,
cadmium, and copper ions, and also the real Gibbs transfer energy of these ions from water into a mixed water ethanol (EtOH)
solution. The surface potential value at the nonaqueous solution/gas phase interface $
\Delta \chi _{H_2 O}^{EtOH}
$
\Delta \chi _{H_2 O}^{EtOH}
was obtained. With account for this value, chemical thermodynamic characteristics of the studied ions in the water-ethanol
solvent were calculated and the effect of composition and nature of the mixed solvent on the values obtained was analyzed.
The dependence of variation in the thermodynamic characteristics of cation resolvation was established on their crystallographic
radius that corresponds to the following sequence: Ca2+ < Cd2+ < Cu2+ < Mg2+. 相似文献
8.
Photooxidation of tryptophan (Trp) in complexes with the uranyl ion upon selective excitation was studied, and the quantum
yields of amino acid oxidation (ϕ(O2)) were determined. It was shown that the photosensitized oxidation of Trp by the uranyl ion involves the chain reaction of
Trp·+ radical cations with O2, rather than follows the commonly accepted mechanism of interaction of the substrate radical cation with the superoxide ion
$
O\overline {_2^ - }
$
O\overline {_2^ - }
. 相似文献
9.
A new approximation has been proposed for calculation of the general temperature integral $
\int\limits_0^T {T^m } e^{ - E/RT} dT
$
\int\limits_0^T {T^m } e^{ - E/RT} dT
, which frequently occurs in the nonisothermal kinetic analysis with the dependence of the frequency factor on the temperature
(A=A
0
T
m). It is in the following form:
$
\int\limits_0^T {T^m } e^{ - E/RT} dT = \frac{{RT^{m + 2} }}
{E}e^{ - E/RT} \frac{{0.99954E + (0.044967m + 0.58058)RT}}
{{E + (0.94057m + 2.5400)RT}}
$
\int\limits_0^T {T^m } e^{ - E/RT} dT = \frac{{RT^{m + 2} }}
{E}e^{ - E/RT} \frac{{0.99954E + (0.044967m + 0.58058)RT}}
{{E + (0.94057m + 2.5400)RT}}
相似文献
10.
The kinetics of acrylic acid oxidation in the presence of iron ions $
(T = 333K,_{P_{O_2 } } = 1 atm)
$
(T = 333K,_{P_{O_2 } } = 1 atm)
has been investigated by measuring the oxygen uptake. The reaction has an induction period τ, after which the O2 uptake is described by the parabolic kinetic law δ[O2]0.5 = b(t − τ). The parameter b characterizing the catalytic oxidation of acrylic acid has been calculated. Upon the introduction of an initiator (azobisisobutyronitrile),
the oxidation has no induction period, but the autoacceleration of the reaction is still observed. A mechanism is suggested
for the process. This mechanism includes initiation due to the interaction of the resulting peroxide and hydroperoxide groups
with Fe2+ and Fe3+ ions and chain termination via the reaction R· + Fe3+, where R· is an acrylic acid macroradical. 相似文献
11.
12.
The adsorption of Cl−, Br−, and I− ions on the renewable liquid In-Ga and Tl-Ga electrodes from 0.1 M solutions in dimethyl formamide (DMF) is investigated
by using the method of differential capacitance measurements. The results are compared with similar data obtained on Hg and
Ga electrodes in DMF and with the corresponding data obtained in acetonitrile (AN). It is shown that, in DMF, the adsorption
parameters and the series of surface activity of halide ions (Hal−) significantly depend on the metal nature. In contrast to Hg electrode, on which the surface activity of halide ions increases
in the series: Cl− < Br− < I−, on In-Ga, as well as on the Ga electrode, it varies in the reverse order: I− < Br− < Cl−, whereas on the Tl-Ga electrode, partially reversed series of surface activity is observed: Br− < I− < Cl−. The results are explained within the framework of Andersen-Bockris model. An analysis of experimental results leads to the
following qualitative conclusions: (1) on the In-Ga and Tl-Ga electrodes, as well as on Ga electrode, free energy of metal-Hal− interaction (
$
\Delta G_{_{M - Hal^ - } }
$
\Delta G_{_{M - Hal^ - } }
) increases in series I− < Br− < Cl−; (2) for Cl−, Br−, and I−,
$
\Delta G_{_{M - Hal^ - } }
$
\Delta G_{_{M - Hal^ - } }
) grows in series Tl-Ga < In-Ga < Ga; (3) an absolute magnitude of $
\Delta G_{_{M - Hal_1^ - } } - \Delta G_{_{M - Hal_2^ - } }
$
\Delta G_{_{M - Hal_1^ - } } - \Delta G_{_{M - Hal_2^ - } }
(Hal1−, and Hal2− are any ions of Cl−, Br−, and I−) increases in series Hg < Tl-Ga < In-Ga < Ga; (4) the metal-DMF chemisorption interaction is much stronger than the metal-AN
interaction and increases in series Tl-Ga < In-Ga < Ga. 相似文献
13.
A new 3D coordination polymer, [LaAg(Pydc)(HPydc)(C2O4)0.5(H2O)2]
n
(I) (H2Pydc = pyridine-3,5-dicarboxylic acid), has been hydrothermally synthesized and characterized by elemental analyses and single
crystal X-ray diffraction. The X-ray diffraction analysis reveals that I (C15H11AgLaN2O12) crystallizes in triclinic space group P
$
\bar 1
$
\bar 1
and features an interesting 3D framework constructed by 2D layers via strong Ag-Ag interactions. Unit cell parameters for
I (n = 1): a = 7.749(2), b = 8.316(1), c = 14.239(3) ?, α = 97.64(2)°, β = 100.12(2)°, γ = 94.37(2)°, and Z = 2. 相似文献
14.
Electrochemical Study on Hydrogen Evolution and
![]() Hydrogen evolution reaction (HER) is the major cathodic reaction which competes
15.
The kinetics of methoxy-NNO-azoxymethane (I) hydrolysis in concentrated solutions of strong acids (HBr, HCl, HClO4, and H2SO4) has been investigated by a manometric method. The gas evolution rate is described by the equation corresponding to two consecutive
first-order reactions, with the rate constant of the second reaction considerably exceeding the rate constant of the first
reaction, i.e., k
2 {ie17-1} k
1. The temperature dependences of k
1 (s−1) in 47.59% HBr in the temperature range from 60 to 90°C and in 64.16% H2SO4 between 80 and 130°C are described by Arrhenius equations with IogA= 12.7 ± 1.5 and 13.6 ± 1.4 and E
a = 115 ± 10 and 137 ± 10 kJ/mol, respectively. The parameters of the Arrhenius equation for the rate constant k
2 for the reaction in 64.16% H2SO4 between 80 and 130°C are IogA= 9.1 ± 2.5 and E
a = 91 ± 18 kJ/mol. An analysis of the UV spectra of compound I in concentrated H2SO4 shows that I is a weak base $
(pK_{BH^ + } \approx - 6)
$
(pK_{BH^ + } \approx - 6)
. The rate-determining step of the hydrolysis of I is the attack of the nucleophile on the carbon atom of the MeO group of the protonated molecule of I. The resulting methyldiazene dioxide decomposes via a complicated mechanism to evolve N2, NO, and N2O. The pseudo-first-order rate constant k
1 of the reaction at 80°C depends strongly on the acid concentration and on the type of nucleophile (Br−, Cl−, or H2O). The relationship between k
1 and the rate constant k of the bimolecular nucleophilic substitution reaction (SN2) is given by the linear equation log$
[k_1 /(C_H + C_{Nu} )] = m^ \ne m*X_0 + \log (k/K_{BH^ + } )
$
[k_1 /(C_H + C_{Nu} )] = m^ \ne m*X_0 + \log (k/K_{BH^ + } )
, where $
C_{H^ + }
$
C_{H^ + }
and C
Nu are the concentrations of H+ and nucleophile, respectively; X
0 is the excess acidity; and m
≠ and m* are coefficients. The Swain-Scott equation log$
(k_{Nu} /k_{H_2 O} ) = ns
$
(k_{Nu} /k_{H_2 O} ) = ns
, where n is the nucleophilicity factor and s is the substrate constant (s = 0.72), is applicable to the rate constants k of the SN2 reactions of the protonated molecule of I with Br−, Cl−, and H2O. 相似文献
16.
T. V. Namsaraeva B. G. Bazarov R. F. Klevtsova L. A. Glinskaya K. N. Fedorov Zh. G. Bazarova 《Russian Journal of Inorganic Chemistry》2010,55(2):209-214
The subsolidus area of Cs2MoO4-Al2(MoO4)3-Zr(MoO4)2 system was studied by X-ray powder diffraction. Two new molybdates with component molar ratios of 1: 1: 1 (S1) and 5:1:2 (S2) were synthesized for the first time. The crystallographic parameters of the 5:1:2 compound were determined. Solution- melt
crystallization and spontaneous nucleation yielded crystals of new 1:1:1 cesium aluminum zirconium molybdate Cs(AlZr0.5)(MoO4)3. Its formula unit and crystal structure were refined by X-ray diffraction (1592 reflections, R=0.0249). Trigonal crystals:
a=12.9441(2) ?, c=12.0457(4) ?, V=1747.86(7) ?3, Z = 6, space group R
$
\bar 3
$
\bar 3
. The three-dimensional combined framework of this structure is formed by MoO4 tetrahedrons linked through common vertices to (Al,Zr)O6 octahedrons. Cesium atoms occupy large cavities of the framework. Crystallographic position M(1) is occupied by randomly
distributed Al3+ and Zr4+ cations. 相似文献
17.
Solubility of RbCl-Rb2SO4-H2O system at 25°C was predicted by using Pitzer ion-interaction model. The mixing parameter was was taken to be zero in the
prediction. The calculated results indicated that the RbCl-Rb2SO4-H2O system is a simple eutonic ternary system at 25°C. This study will provide the theoretical basis for the extraction of rubidium
from salt lake brines in Qinghai and Tibet Plateau. 相似文献
18.
F. Bousmina L. Zayani D. Ben Hassen-Chehimi N. Kbir-Ariguib M. Trabelsi-Ayedi 《Monatshefte für Chemie / Chemical Monthly》2003,4(10):763-768
The diagram of the ternary system Mg2+/Cl−, SO4 2−–H2O was established at 15°C by means of analytical and conductimetric measurements. Three compounds were found in this diagram, which are MgSO4·6H2O, MgSO4·7H2O, and MgCl2·6H2O. The solubility field of MgSO4·7H2O is important whereas those of MgSO4·6H2O and MgCl2·6H2O are small. The compositions (mass-%) of the two invariant points determined by the two methods are: MgSO4:MgCl2=2.73:33.80 and MgSO4: MgCl2=3.38:28.91. Both the measured and the calculated isotherm at 15°C have been used for modelling of the diagram Mg2+/Cl−, SO4 2−–H2O between 0 and 35°C. The polythermal invariant point was approximately located between 15 and 10°C. 相似文献
19.
Gamma Ray Radiation Effect on
![]() The development of
20.
Theoretical Investigations on Photodissociation Dynamics of Deuterated Alkyl Halides CD3CH2F
![]() The product branching ratio between different products in multichannel reactions is as important as the overall rate of reaction, both in terms of practical applications (\emph{e.g}. models of combustion or atmosphere chemistry) in understanding the fundamental mechanisms of such chemical reactions. A global ground state potential energy surface for the dissociation reaction of deuterated alkyl halide CD
|