共查询到20条相似文献,搜索用时 15 毫秒
1.
The ab initio quantum chemical method MP2 with a 6-311++G(d, p) basis set is used to calculate the energy of gas-phase solvation of the H2Cl4+ cation and Cl4− anion by one perchloric acid molecule. The energy of additional solvation of the resulting complexes by liquid perchloric
acid is estimated within the continuum model of solvation by the PCM method, with the acid modeled as a continuum with a large
dielectric constant of ɛ = 115. The calculated data have provided an almost quantitative estimate for the energy of selfionization
of 100% liquid perchloric acid. The similarly calculated energy of solvation of protons by 100% perchloric acid is 30.7 kcal/mol
lower than the heat of hydration of protons in aqueous solution. This result explains the fact that anhydrous perchloric acid
exhibits the properties of a superacid. 相似文献
2.
The energies of gas-phase solvation of the FSO3H 2 + , and ClSO3H 2 + cations and FSO 3 ? , ClSO 3 ? anions by one molecule of the respective acid (FSO3H or ClSO3H) have been calculated by a quantum chemical method taking into account electron correlation in terms of MP2 theory with a 6-311++G(d,p) basis set. The energy of additional solvation of the resulting complexes by liquid acid has been estimated within the continuum model of solvation by the IPCM method, with the acid modeled as a continuum with a large dielectric constant. The calculated data have provided a quantitative estimate for the energy of self-ionization of liquid FSO3H and ClSO3H acids. The similarly calculated energy of solvation of protons in 100% fluorosulfonic and chlorosulfonic acids is lower than the heat of hydration of the proton in aqueous solution by 23.4 and 24.5 kcal/mol, respectively. These quantum chemical data explain why 100% liquid fluorosulfonic and chlorosulfonic acids exhibit the properties of a superacid. 相似文献
3.
The surface region of sulfate aerosols (supercooled aqueous concentrated sulfuric acid solutions) is the likely site of a number of important heterogeneous reactions in various locations in the atmosphere, but the surface region ionic composition is not known. As a first step in exploring this issue, the first acid ionization reaction for sulfuric acid, H2SO4 + H2O HSO4– + H3O+, is studied via electronic structure calculations at the Hartree–Fock level on an H2SO4 molecule embedded in the surface region of a cluster containing 33 water molecules. An initial H2SO4 configuration is selected which could produce H3O+ readily available for heterogeneous reactions, but which involves reduced solvation and is consistent with no dangling OH bonds for H2SO4. It is found that at 0 K and with zero-point energy included, the proton transfer is endothermic by 3.4 kcal/mol. This result is discussed in the context of reactions on sulfate aerosol surfaces and, further, more complex calculations.Contribution to the Jacopo Tomasi Honorary Issue 相似文献
4.
N. N. Kuranova S. V. Dushina V. A. Sharnin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(5):792-795
The enthalpies of stepwise protonation of nicotinate ion (L−) in water-ethanol solvents were determined calorimetrically at 298.15 K. It was found that the reduced exothermicity of the
reaction of nicotinate ion protonation upon an increase of the organic component content in solution is due mainly to increased
solvation of the proton. The minor influence of solvent on the enthalpy of protonation of nicotinic acid (HL) is characterized
by compensation from solvation of the proton, the ligand, and its protonated form (H2L+). 相似文献
5.
G. L. Sharipov A. M. Abdrakhmanov R. Kh. Gainetdinov 《Russian Chemical Bulletin》2005,54(8):1793-1797
A comparative study of the sonoluminescence spectra of water and argon-saturated aqueous H2SO4 solutions was carried out. At an H2SO4 concentration of 18 mol L−1, the sulfuric acid sonoluminescence is fifty times more intense than water sonoluminescence. The sulfuric acid luminescence
spectrum differs from the water sonoluminescence spectrum caused by the emission of excited water molecules and OH radicals
from the gas phase of cavitation bubbles. The sulfuric acid sonoluminescence spectrum exhibits maxima at 330, 420, 500, and
630 nm. Emitters of sonoluminescence of sulfuric acid are the singlet (330–340 nm) and triplet (∼420 nm) excited SO2 molecules formed by sonolysis of H2SO4 molecules. Another product of sonolysis of H2SO4, atomic oxygen, is assumed to be responsible for the luminescence at λ = 630 nm.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1742–1745, August, 2005. 相似文献
6.
Mauricio P. de Paula Talita M. Lacerda Márcia D. Zambon Elisabete Frollini 《Cellulose (London, England)》2012,19(3):975-992
The present work is inserted into the broad context of the upgrading of lignocellulosic fibers. Sisal was chosen in the present
study because more than 50% of the world’s sisal is cultivated in Brazil, it has a short life cycle and its fiber has a high
cellulose content. Specifically, in the present study, the subject addressed was the hydrolysis of the sisal pulp, using sulfuric
acid as the catalyst. To assess the influence of parameters such as the concentration of the sulfuric acid and the temperature
during this process, the pulp was hydrolyzed with various concentrations of sulfuric acid (30–50%) at 70 °C and with 30% acid
(v/v) at various temperatures (60–100 °C). During hydrolysis, aliquots were withdrawn from the reaction media, and the solid
(non-hydrolyzed pulp) was separated from the liquid (liquor) by filtering each aliquot. The sugar composition of the liquor
was analyzed by HPLC, and the non-hydrolyzed pulps were characterized by viscometry (average molar mass), and X-ray diffraction
(crystallinity). The results support the following conclusions: acid hydrolysis using 30% H2SO4 at 100 °C can produce sisal microcrystalline cellulose and the conditions that led to the largest glucose yield and lowest
decomposition rate were 50% H2SO4 at 70 °C. In summary, the study of sisal pulp hydrolysis using concentrated acid showed that certain conditions are suitable
for high recovery of xylose and good yield of glucose. Moreover, the unreacted cellulose can be targeted for different applications
in bio-based materials. A kinetic study based on the glucose yield was performed for all reaction conditions using the kinetic
model proposed by Saeman. The results showed that the model adjusted to all 30–35% H2SO4 reactions but not to greater concentrations of sulfuric acid. The present study is part of an ongoing research program, and
the results reported here will be used as a comparison against the results obtained when using treated sisal pulp as the starting
material. 相似文献
7.
Abstract
A proton-conductive supramolecular complex, {[Cu(H2O)8][H(H2O)3](HINO)4(PMo12O40)} n , was constructed by a self-assembly of H+(H2O)3 clusters, [Cu(H2O)8]2+ clusters, [PMo12O40]3− anions, and isonicotinic acid N-oxide (HINO). Single-crystal X-ray diffraction analysis at 293 K revealed that the complex presented the three-dimensional (3D) supramolecular framework built from non-covalent interactions. Interestingly, [PMo12O40]3− anions self-assembled into poly-Keggin-anion chains in the supramolecular framework. Thermogravimetric analysis shows no weight loss in the temperature range of 20–100 °C, indicating that all water molecules in the unit structure are not easily lost below 100 °C. Surprisingly, the proton conductivity of the complex in the temperature range of 85–100 °C under 98% RH condition reached good proton conductivity of 10−3 S cm−1. A possible mechanism of the proton conduction was proposed according to the experimental results. 相似文献8.
V. D. Maiorov I. S. Kislina G. I. Voloshenko N. B. Librovich 《Russian Chemical Bulletin》2000,49(9):1526-1530
Complex formation in the trifluoroacetic acid (TFA)—DMF system containing TFA from 0 to 100 mol.% was studied by IR multiple attenuated total reflectance (MATR) spectroscopy at 30°C. The formation of uncharged 1∶1 TFA—DMF complexes with a quasi-ion structure and partial proton transfer to the O atom of the DMF molecule (quasi-ion pairs) were observed in the TFA—DMF system with the TFA content from 0 to 90 mol%. Depending on the ratio of the components, the quasi-ion pairs are solvated by the DMF or TFA molecules. The solvation of the quasi-ion pairs slightly changes the parameters of the central strong H bond. When the acid concentration reaches 80 mol.%, the proton adds to the DMF molecule to form the ion pair (DMF)H+·(A...H...A)−, whose anion contains a strong symmetric H bond. 相似文献
9.
A new method of synthesis 2,2-dimethylolpropionic acid from 2,2-dimethylolpropionaldehyde was put forward. The electrochemical
oxidation behavior of 2,2-dimethylolpropionaldehyde has been investigated on a Ti/SnO2 + Sb2O4/PbO2 electrode by cyclic voltammetry (CV) and stable polarization curves in sulfuric acid. The results showed that it was an irreversible
reaction controlled by diffusion. The formation mechanism of 2,2-dimethylolpropionic acid in the sulfuric acid was then proposed
and the transfer coefficients of the reaction were calculated. It was concluded that RCHO+ỌHads→RCHOỌHads was the rate-determining step in the electrolysis process. The rate of this step obtained from the assumed process agrees
well with experiment. 相似文献
10.
N. M. Vitkovskaya V. B. Kobychev E. Yu. Larionova B. A. Trofimov 《Russian Chemical Bulletin》1999,48(1):35-41
The pathways of migration of the multiple bond in propene and propyne molecules involving the hydroxide ion were investigated
by theab initio (RHF/6-31+G* and MP2/6-31+G*) methods. Stationary points corresponding to stable complexes between the molecules under study and the hydroxide ion and
between corresponding carbanions and water molecule were found on the potential energy surfaces of the proton transfer reactions.
In the presence of hydroxide ion, migration of the multiple bond can occur by an “intramolecular” mechanism of the proton
transfer involving the proton of hydroxide ion bound in the complex with propene or propyne molecule. For the propene system,
such a mechanism seems to be quite realistic and more preferable energetically than a traditional two-stage mechanism with
a passage of the proton into the medium. For the system with the triple bond, an equal expenditure of energy is required to
follow any mechanism (without taking into account the effects of solvation and the interaction with a cation), whereas the
formation of the stable [H2C=C=CH·H2O]− complex can prevent further transformations.
For Part 1, see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–41, January, 1999. 相似文献
11.
Wolfgang Förner Peter Otto Julius Bernhardt János J. Ladik 《Theoretical chemistry accounts》1981,60(3):269-281
We have performed calculations of the glycine zwitterion surrounded by water molecules with the help of the mutually consistent
field (MCF) method and perturbation theoretical expressions. Two different models for the hydration shell have been chosen,
the glycine·6H2O and glycine·12H2O complexes, representing the most probable first and second solvation shell, respectively. To calculate the exchange and
charge transfer energy contributions we have applied approximative expressions derived from perturbation theory for weakly
overlapping subunits. For the sake of comparison we also calculated the interaction energy in the supermolecule approach for
the smaller of the two solvation complexes. Furthermore, we have investigated the part of the potential energy surface which
is determined by varying the lengths of the hydrogen bonds between glycine and water in the complex glycine·12H2O using the electrostatic approach. The exchange energy contribution to the interaction energy for different points on the
surface was approximated with the help of an analytical expression fitted to three directly calculated points. For the charge
transfer energy a polynomial expansion of second order was established on the basis of five values, computed with the aid
of the perturbation theoretical expression. To get a more detailed insight in the relatively strong hydrogen bonds between
the water molecules and the ionic hydrophilic parts of glycineab initio model studies on NH
4
+
·3H2O and HCOO−·3H2O systems are reported. 相似文献
12.
Prof. Dr. Ryo Kanzaki Hitoshi Kodamatani Takashi Tomiyasu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(59):13500-13503
In order to investigate the proton solvation state in protic ionic liquids (PILs), ten acid dissociation enthalpies and entropies of eight compounds were determined in ethylammonium nitrate (EAN). Regardless of the nature of the compound, 24 kJ mol−1 larger enthalpy and 65 J mol−1 K−1 larger entropy than those in water, respectively, were observed. These values were reasonably explained by the differences in the proton solvation structure in EAN and water. Namely, protons in EAN exist as HNO3, having a higher reaction energy than that of H3O+ in water, undergo entropic stabilization as a result of the less-structured solvation. As such, the entropic effect of the proton solvation structure on the acid–base property is possibly applicable to all PILs. In addition, based on these proton thermodynamics, enthalpy and entropy windows were proposed as a novel perspective for the characterization of solvents. Use of this concept enabled the visualization of similarities and differences between EAN and water. 相似文献
13.
Ye Qin Wei-Feng Xue Jian-Guo Liu Wei-Guo Xu Chuan-Wei Yan Jia-Zhen Yang 《Journal of solution chemistry》2010,39(6):857-863
The molar enthalpies of solution of VOSO4⋅3.52H2O(s) at various molalities in water and in aqueous sulfuric acid (0.1 mol⋅kg−1), Δsol
H
m, were measured by a solution-reaction isoperibol calorimeter at 298.15±0.01 K. An improved Archer’s method to estimate the
standard molar enthalpy of solution, DsolH0m\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}, was put forward. In terms of the improved method, the values of DsolH0m=-24.12±0.03 kJ·mol-1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-24.12\pm 0.03~\mbox{kJ}{\cdot}\mbox{mol}^{-1} of VOSO4⋅3.52H2O(s) in water and DsolH0m=-15.38±0.06 kJ·mol-1\Delta_{\mathrm{sol}}H^{0}_{\mathrm{m}}=-15.38\pm 0.06~\mbox{kJ}{\cdot}\mbox{mol}^{-1} in aqueous sulfuric acid were obtained, respectively. The data indicates that the energy state of VOSO4 in aqueous H2SO4 is higher than that in pure water. 相似文献
14.
A. K. Arof N. E. A. Shuhaimi N. A. Alias M. Z. Kufian S. R. Majid 《Journal of Solid State Electrochemistry》2010,14(12):2145-2152
In this work, a chitosan/iota (ι)-carrageenan blended film doped with orthophosphoric acid (H3PO4) as ionic dopant and poly(ethylene glycol) (PEG) as plasticizer has been used as a separator and electrolyte in an electrical
double layer capacitor (EDLC). A set of samples were prepared by the solution cast technique to see the effect of the different
weight ratios of the proton donor and plasticizer on the conductivity. The highest conducting sample has composition 37.50 wt.%
chitosan–37.50 wt.% ι-carrageenan–18.75 wt.% H3PO4–6.25 wt.% PEG. The conductivity value is 6.29 × 10−4 S cm−1. The conductivity–temperature relationship is Arrhenian, and the activation energy for the highest conducting sample is 0.09 eV.
The specific discharge capacitance of the EDLC is 35 F g−1 at 0.11 mA cm−2 current drain and was constant for 30 cycles. 相似文献
15.
The intrinsic energy barrier for proton transfer in a model carbon acid-base system, H3O+ + CH2 =CH2, is calculated. The role of basis sets, correlation energy, and solvation are discussed. The results are analyzed within the context of the use of the Marcus equation to characterize proton-transfer kinetics. 相似文献
16.
Thermal explosion simulation and incompatible reaction of dicumyl peroxide by calorimetric technique
Sun-Ju Shen Sheng-Hung Wu Jen-Hao Chi Yih-Wen Wang Chi-Min Shu 《Journal of Thermal Analysis and Calorimetry》2010,102(2):569-577
Dicumyl peroxide (DCPO) is usually employed as an initiator for polymerization, a source of free radicals, a hardener, and
a linking agent. In Asia, due to its unstable reactive nature, DCPO has caused many thermal explosions and runaway reaction
incidents in the manufacturing process. This study was conducted to elucidate its essentially thermal hazard characteristics.
In order to analyze the runaway behavior of DCPO in a batch reactor, thermokinetic parameters, such as heat of decomposition
(ΔH
d) and exothermic onset temperature (T
0), were measured via differential scanning calorimetry (DSC). Thermal runaway phenomena were then thoroughly investigated
by DSC. The thermokinetics of DCPO mixed with acids or bases were determined by DSC, and the experimental data were compared
with kinetics-based curve fitting of thermal safety software (TSS). Solid thermal explosion (STE) and liquid thermal explosion
(LTE) simulations of TSS were applied to determine the fundamental thermal explosion behavior in large tanks or drums. Results
from curve fitting indicated that all of the acids or bases could induce exothermic reactions at even an earlier stage of
the experiments. In order to diminish the extent of hazard, hazard information must be provided to the manufacturing process.
Thermal hazard of DCPO mixed with nitric acid (HNO3) was more dangerous than with other acids including sulfuric acid (H2SO4), phosphoric acid (H3PO4), and hydrochloric acid (HCl). By DSC, T
0, heat of decomposition (ΔH
d), and activation energy (E
a) of DCPO mixed with HNO3 were calculated to be 70 °C, 911 J g−1, and 33 kJ mol−1, respectively. 相似文献
17.
Piaoping Yang Jianfeng Yu Zhenlü Wang Qingsheng Liu Xuwei Yang Tonghao Wu 《Reaction Kinetics and Catalysis Letters》2005,85(1):153-159
Summary FT-IR and 29Si-NMR studies suggested the interaction of H2SO4 with the SiO2 support in the material synthesized by the sol-gel method. 1H-NMR results showed that the acid strength of solid sulfuric acid was almost the same as that of liquid sulfuric acid. The catalyst showed higher catalytic activity and stability than that prepared by impregnation method. 相似文献
18.
D. B. Vasil’chenko S. V. Korenev I. A. Baidina V. A. Drebushchak N. K. Moroz S. G. Kozlova A. S. Ulikhin N. F. Uvarov 《Russian Journal of Electrochemistry》2011,47(5):631-636
The method of deposition from solutions was used to synthesize [RhL
4Cl2]HSO4 · nH2SO4 · mH2O complex salts (L = Py, γ-picoline), n ≈ 0.5−0.6, m ≈ 5−6. According to the data of X-ray phase analysis, the crystal structure of these salts is formed by layers of cations
separated by layers consisting of anions molecules of sulfuric acid and water connected through a system of hydrogen bonds.
Calorimetric methods were used to study phase transitions and the range of thermal stability of salts. The method of 1H NMR spectroscopy discovered that protons within the {HSO4− · nH2SO4 · mH2O} subsystem featured enhanced conductivity. Conductivity studies showed that trans-[RhL
4Cl2]HSO4 · nH2SO4 · mH2O samples had high proton conductivity. 相似文献
19.
Zyubina T. S. Shilov G. V. Dobrovol'skii Yu. A. Leonova L. S. Mebel' A. M. 《Russian Journal of Electrochemistry》2003,39(4):376-385
Orthoperiodic and orthotelluric acids, their salts MIO6H4 (M = Li, Rb, Cs) and CsH5TeO6, and dimers of the salt · acid type are calculated within density functional theory B3LYP and basis set LanL2DZ complemented by the polarizationd,p-functions. According to calculations, the salt · acid dimerization is energetically favorable for compounds MIO6H4 · H5IO6 (M = Rb, Cs) and CsIO6H4 · H6TeO6. The dimerization energy is equal to 138–146 kJ mol–1. With relatively small activation energies equal to 4 kJ mol–1 (M = Li) and 11 kJ mol–1 (M = Rb, Cs), possible is rotation of octahedron IO6 relative to the M atom in monomers of salt molecules. The proton transfer along an octahedron occurs with activation energies of 63–84 kJ mol–1. The activation energy for the proton transfer between neighboring octahedrons of the type salt · acid acid · salt equals 8–17 kJ mol–1. Quantum-chemical calculations nicely conform to x-ray diffraction and electrochemical data. 相似文献
20.
Won Ju Phang Woo Ram Lee Kicheon Yoo Dae Won Ryu Dr. BongSoo Kim Prof. Chang Seop Hong 《Angewandte Chemie (International ed. in English)》2014,53(32):8383-8387
A porous metal–organic framework (MOF), [Ni2(dobdc)(H2O)2]?6 H2O (Ni2(dobdc) or Ni‐MOF‐74; dobdc4?=2,5‐dioxido‐1,4‐benzenedicarboxylate) with hexagonal channels was synthesized using a microwave‐assisted solvothermal reaction. Soaking Ni2(dobdc) in sulfuric acid solutions at different pH values afforded new proton‐conducting frameworks, H+@Ni2(dobdc). At pH 1.8, the acidified MOF shows proton conductivity of 2.2×10?2 S cm?1 at 80 °C and 95 % relative humidity (RH), approaching the highest values reported for MOFs. Proton conduction occurs via the Grotthuss mechanism with a significantly low activation energy as compared to other proton‐conducting MOFs. Protonated water clusters within the pores of H+@Ni2(dobdc) play an important role in the conduction process. 相似文献