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1.
The B3LYP and MP2 methods with 6-31G* basis set were used to predict the geometries of N, N-dimethylformamide (DMF) dimer and DMF–aromatic hydrocarbons interaction systems. A total of 10 conformers were obtained with
no imaginary frequencies, respectively. The interaction energies of these binary mixtures have been obtained. The analyses
of chelpg charge distribution and the atoms in molecules theory (AIM) were used to analyze the nature of the interaction.
The results show the presence of hydrogen bonds between DMF and aromatic hydrocarbons. The interaction between DMF and benzonitrile
is the strongest with the interaction energy of −21.58 kJ mol−1 (BSSE corrected), and the intensity order of interactions is DMF–benzonitrile: d2 > DMF–DMF: a2 > DMF–toluene: c1 > DMF–benzene:
b2. 相似文献
2.
The stability of hydrogen-bonded complexes, DMF–H
n
CCl4−n
(n = 1–3), has been investigated by several theoretical methods including the MP2 level of ab initio theory at various basis
sets from 6-31+G* to 6-311++G**. Two stable configurations (respectively a and b) were obtained for each complex with no imaginary frequencies. The minimum energy structure of these complexes has also been
analyzed by means of the atoms in molecule theory at MP2/6-311++G** level. It is found that C–H···O hydrogen bonding exists
in these systems and that the intensity of HB interaction gradually increases with successive chlorination. Computed results
indicate that these complexes automatically assemble into different stable configurations. For the complexes under consideration,
their stabilities can be mainly ascribed to the intermolecular HB interaction. The present work is helpful to clearly understand
the interaction mechanism of these complexes in theory. 相似文献
3.
In this article, a binderless dealuminated HZSM-5 zeolite (Si/Al = 41.4) was used as a catalyst for the isomerization of a mixture of ethylbenzene and xylene. The experimental results indicated that at low residence times the catalyst is effective to isomerize the ethylbenzene into xylenes. A comprehensive kinetic model considering chemisorption, surface chemical reactions, and diffusional processes was developed for this reaction. The intrinsic activation energy (71.99 kJ mol−1) for the surface reaction of ethylbenzene into m-xylene was calculated for the first time, and the corresponding intrinsic activation energies for o-xylene to m-xylene and m-xylene to p-xylene surface reactions were calculated to be 59.45 and 50.68 kJ mol−1, respectively. Lower apparent values have been reported in the literature, and we rationalize that they correspond to multistep processes and intrinsically include a negative activation energy pertaining to chemisorption. The results also revealed that the ethylbenzene diffusion within the zeolite channels was four orders of magnitude smaller than p-xylene. 相似文献
4.
Anil Kumar Nain 《Journal of solution chemistry》2008,37(11):1541-1559
The Kirkwood–Buff (K-B) integrals play an important role in characterizing the intermolecular interactions in liquid mixtures.
The interaction is represented by the K-B parameters, G
AA,G
BB, and G
AB, which reflect correlation between like-like and like-unlike species in the mixture. The K-B integrals of binary mixtures
of tetrahydrofuran with benzene, toluene, o-xylene, m-xylene, p-xylene and mesitylene at 298.15 K and atmospheric pressure have been computed from the experimental data of ultrasonic speed
and density. We have used the similar inverse procedure (as proposed by Ben-Naim) to compute the K-B parameters of the mixture,
in which thermodynamic information on mixtures, such as partial molar volumes, isothermal compressibility and experimental
data of partial vapor pressures were used. A new route has been incorporated by using regular solution theory in the computation
of excess Gibbs energy for obtaining the partial vapor pressures of binary liquid mixtures. The low values of excess entropy,
S
E≈0, obtained for these mixtures indicate the applicability of regular solution theory to the mixtures. The values of the K-B
parameter, G
AB, obtained using this procedure indicate that the correlation/affinity between THF and aromatic hydrocarbon molecules follows
the order: benzene > toluene > o-xylene > m-xylene > p-xylene > mesitylene, which is in good agreement with the results obtained from the trends exhibited by the excess functions
of these mixtures. 相似文献
5.
《Physics and Chemistry of Liquids》2012,50(2):149-156
Vapour pressures of butyl acetate?+?benzene or toluene or o- or m- or p-xylene were measured by static method at 298.15?±?0.01?K over the entire composition range. The activity coefficients and excess molar Gibb's free energies of mixing (G E) for these binary mixtures were calculated by fitting vapour pressure data to the Redlich–Kister equation using Barker's method of minimizing the residual pressure. The G E values for the binary mixtures containing benzene are positive; while these are negative for toluene, ortho, meta and para xylene system over the whole composition range. The G E values of an equimolar mixture for these systems vary in the order: benzene?>?m-xylene?>?o-xylene?>?p-xylene?>?toluene 相似文献
6.
A.S. Araujo T.B. Domingos M.J.B. Souza A.O.S. Silva 《Reaction Kinetics and Catalysis Letters》2001,73(2):283-290
The catalytic isomerization of m-xylene was studied over a solid acid silicoaluminophosphate type SAPO-11, mixed to HZSM-5 zeolite. The reaction was processed
varying the temperature and weight hourly space velocity, using a fixed bed continuous flow reactor. The m-xylene suffers isomerization to p-xylene and o-xylene by molecular displacement of methyl groups. The mixed catalyst was selective to p-xylene at 623 K and 2.5 h−1 with a maximum p/o ratio of 2.05. The ethylbenzene formation was not observed in the products. In this process an apparent activation energy
of the order of 13.9 kJ mol−1 was obtained.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
7.
Zhi Qiang Shi Ning Ning Ji Ren Gao Zhao Ji Kun Li Zhi Feng Li 《Structural chemistry》2011,22(1):225-233
Two new copper(II) complexes, [Cu(p-FBA)2(2,2′-bpy)]·(H2O) (1) and [Cu(p-FBA)(2,2′-bpy)2]·(p-FBA)2 (2) {p-FBA = p-fluorobenzoic acid, 2,2′-bpy = 2,2′-bipyridine} have been obtained from an identical starting mixture using temperature as
the only independent variable and characterized by X-ray single crystal diffraction as well as with infrared spectroscopy,
elemental analysis, and thermogravimetric analysis. The results reveal that 1 has 1D infinite chain structure formed by O–H···O hydrogen bonds, while 2 features a 0D structure. Additionally, there exist C–H···O hydrogen bonds and π–π stacking interactions in 1, forming 2D supramolecular structure. Furthermore, density functional theory (DFT) calculations of the structures, stabilities,
orbital energies, composition characteristics of some frontier molecular orbitals and Mulliken charge distributions of the
[Cu(p-FBA)2(2,2′-bpy)] of 1 and [Cu(p-FBA)(2,2′-bpy)2]+ cation of 2 were performed by means of Gaussian 03W package and taking B3LYP/lanl2dz basis set. 相似文献
8.
Densities of sodium nitrobenzoate (o-, m-, p-) have been measured in dimethylformamide (DMF)–water mixtures at 298.15 K with an oscillating-tube densimeter. From these densities, apparent molar volumes of sodium nitrobenzoate in DMF–H2O-mixtures have been calculated and partial molar volumes at infinite dilution have been evaluated. Substituent and solvent effects on the transfer volumes of each isomer from water to DMF–H2O-mixed solvents have also been obtained. The results are explained in terms of solvent–solvent and solute–solvent interactions. 相似文献
9.
Abstract The molecular and crystal structure of a 1:1 co-crystal of 4,4′-dimethyl-7,7′-bi([1,2,5]thiadiazolo[3,4-b]pyridylidene)–chloranilic acid, (1), has been determined by X-ray diffraction at the monoclinic space group P21/c with cell parameters of a = 8.422(6), b = 7.343(4), c = 16.112(7) ?, β = 104.988(8)°, V = 962.5(10) ?3 and Z = 2. In the crystal structure, two components connect via the intermolecular O–H···N hydrogen bonds [2.804(4) ?] and S···O
heteroatom interaction [2.945(3) ?] with R
2
2(7) couplings to form a unique and infinite one-dimensional supramolecular tape structure. The calculations of (1) at the HF/6-31G(d), MP2/6-31G(d), and B3LYP/6-31G(d) levels can almost reproduce X-ray geometry. In addition, the distances
of the intermolecular O–H···N and S···O interactions by MP2/6-31G(d) and B3LYP/6-31G(d) levels agree well with those in the
crystal. The calculated binding energies corrected BSSE and ZPE are −4.487 (HF), −7.473 (MP2), and −5.640 (B3LYP) kcal/mol.
The results suggest that the complex (1) is very stable and the dispersion interaction is significantly important for the attractive intermolecular interaction in
(1). The NBO analysis has revealed that the n(N) → σ*(O–H) interaction gives the strongest stabilization to the system and the major interaction for the intermolecular
S···O contact is n(O) → σ*(S–N).
Index Abstract In the crystal structure of the title compound, the molecules are linked by intermolecular O–H···N hydrogen bonds and short
S···O heteroatom interactions with R
2
2(7) couplings to construct a unique and infinite one-dimensional supramolecular tape structure.
相似文献
10.
Processes for the production of xylenes, which occur in an integrated aromatic complex, are discussed. A brief overview of the work carried out at Indian Petrochemicals Corporation Limited for the development of zeolite-based catalytic processes for the production of aromatics is presented. This includes xylene isomerization, transalkylation and disproportionation of C7 and C9 aromatics for maximization of xylenes, selective disproportionation of toluene and selective alkylation of mono-alkylaromatics to p-dialkylbenzene. Achievements in the commercialization of zeolite-based catalysts and processes for isomerization of m-xylene to p- and o-xylene along with dealkylation of ethylbenzene, and for selective ethylation of ethylbenzene to produce p-diethylbenzene are highlighted. 相似文献
11.
The hydrogen bonding interactions between cysteine and N,N-dimethylformamide (DMF) were studied at the extended hybrid functional DFT-X3LYP/6-311++G(d,p) level regarding their geometries,
energies, vibrational frequencies, and topological features of the electron density. The quantum theory of atoms in molecules
(QTAIM) and natural bond orbital (NBO) analyses were employed to elucidate the interaction characteristics in the complexes.
The results show that two intermolecular hydrogen bonds (H-bonds) are formed in one complex except few complexes with one
intermolecular H-bond. The H-bonds involving O atom of DMF as H-bond acceptor usually are red-shifting H-bonds, while the
blue-shifting H-bond usually involve methyl of DMF or methenyl of cysteine moiety as H-bond donors. Both hydrogen bonding
interaction and structural deformation play important roles in the relative stabilities of the complexes. Due to the π-bond
cooperativity, the strongest H-bond is formed between hydroxyl of cysteine moiety and O atom of DMF, however, the serious
deformation counteract the hydrogen bonding interaction to a great extent. The complex involves a stronger hydrogen bonding
interaction as well as the smaller deformation is the most stable one. The electron density (ρb) as well as its Laplacian (∇2ρb) at the H-bond critical point predicted by QTAIM is strongly correlated with the H-bond structural parameter (δR
H···Y) and the second-perturbation energies E(2) in the NBO scheme. 相似文献
12.
Wen-Kui Dong Jun-Feng Tong Yin-Xia Sun Jian-Chao Wu Jian Yao Shang-Sheng Gong 《Transition Metal Chemistry》2010,35(4):419-426
Two new mono- and dinuclear Cu(II) complexes, namely [CuL1]·0.5H2O (1) and [(Cu2(L2)2)(DMF)]·0.5DMF (2) (H2L1 = 1,2-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)]methylene-aminooxy}ethane; H2L2 = 1,3-bis{[(Z)-(3-methyl-5-oxo-1-phenyl-1H-pyrazolidin-4(4H)-yl)(phenyl)] methyleneaminooxy}propane), have been synthesized and characterized by X-ray crystallography. The unit cell
of complex 1 contains two crystallographically independent but chemically identical [CuL1] molecules and one crystalline water molecule, showing a slightly distorted square-planar coordination geometry and forming
a wave-like pattern running along the a-axis via hydrogen bonding and π···π stacking interactions. Complex 2 has a dinuclear structure, comprising two Cu(II) atoms, two completely deprotonated phenolate bisoxime (L2)2− moieties (in the form of enol), and both coordinated and hemi-crystalline DMF molecules. Complex 2 has square-planar and square-pyramidal geometries around the two copper centers, whose basic coordination planes are almost
perpendicular and form an infinite three-dimensional supramolecular network structure involving intermolecular C–H···N, C–H···O,
and C–H···π(Ph) hydrogen bonding and π···π stacking interactions of neighboring pyrazole rings. 相似文献
13.
V. I. Baranov L. A. Gribov V. E. Dridger M. Kh. Iskhakov I. V. Mikhailov 《High Energy Chemistry》2009,43(5):362-369
The possibility of construction of a semiempirical method for simulation of photochemical processes and calculation of quantum
yields of reactions has been studied. The practicability of the approach was demonstrated for the o-xylene → m-xylene, m-xylene → p-xylene, m-xylene → o-xylene, and o-diethylbenzene → m-diethylbenzene photoisomerization reactions as an example. The calculated quantum yields of the reactions are in qualitative
agreement with experimental data. 相似文献
14.
四氯合铂酸钾分别与邻、间、对磺基苯甲酸在乙腈和水中利用水热合成获得了3个铂的N-(1-亚氨基乙基)乙脒配合物:[Pt(NIA)_2]·(2-sb)·2H_2O(1),[Pt(NIA)_2]·(3-sb)·3H_2O(2)和[Pt(NIA)_2]·(1,4-dsb)·2H_2O(3)(NIA=N-(1-亚氨基乙基)乙脒,2-sb~2-=2-磺基苯甲酸二价阴离子、3-sb~2-=3-磺基苯甲酸二价阴离子、1,4-dsb~2-=1,4-二磺基苯二价阴离子)。合成过程中发生了乙氰三聚以及4-sb~2-转变为1,4-dsb~2-的反应。对配合物进行了元素分析、红外、紫外、荧光、热重和粉末X射线衍射表征,并利用单晶X射线衍射测定了配合物的晶体结构。3个配合物为阳离子-阴离子物种,阳离子为[Pt(NIA)_2]~(2+),中心金属离子四配位平面构型;阴离子与阳离子、水形成氢键,组成一个三维网络结构,但3个配合物的氢键模式不同。配合物在热稳定性、荧光性质上有一定差异。 相似文献
15.
Liping Yang Hanbang Liu Jiacheng Xing Dr. Danhua Yuan Prof. Dr. Yunpeng Xu Prof. Dr. Zhongmin Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(20):6187-6190
Xylene isomer separation is considered one of the seven separation challenges that changed the world. In addition, the high-energy demand of xylene separation highlights the need for efficient novel adsorbents. Herein, the liquid-phase separation potential of the anion-pillared hybrid material SIFSIX-1-Cu was studied for preferential adsorption of o-xylene and m-xylene over p-xylene, which was inspired by a previous complexation crystallization method for separating m-xylene. We report detailed experimental liquid-phase adsorption experiments, yielding selectivities of 3.0 for o-xylene versus p-xylene and 2.6 for m-xylene versus p-xylene. Our theoretical calculations thus provide a reasonable explanation that the xylene adsorption selectivity is attributed to the C−H⋅⋅⋅F interaction, and the host–guest interaction order agrees with the adsorption priority: o-xylene > m-xylene > p-xylene. 相似文献
16.
A. Özbay S. Sağlam T.R. Sertbakan E. Kasap S. Özçelik 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):49-54
Infrared spectra of M(1,10-diaminodecane)Ni(CN)4 · 1,5 G (M=Co, Ni or Cd; G=o-xylene, m-xylene, p-xylene) and Cd(l,6-diaminohexane)M(CN)4 · C6H6 (M=Cd or Hg) clathrates are reported. The 1,10-diaminodecane and 1,6-diaminohexane molecules in the host permit the inclusion
of bulky guest molecules. The spectral data of clathrates were compared with those of the corresponding host. The spectral
features suggest that these compounds are similar in structure to other Hofmann-type and Hofmann-Td type clathrates, respectively. 相似文献
17.
It was recently shown that complexes of the type F–Cl···CN–R, ostensibly halogen bonded, sometimes have properties (relatively
high binding energies, short Cl–C separations and considerably lengthened F–Cl distances) that are inconsistent with typical
halogen bonds (Del Bene et al. in J Phys Chem A 114:12958–12962, 2010). We attribute these anomalous features, as well as analogous observations for F–Cl···SiN–R systems, to the strong polarization
of the CN–R carbons and SiN–R silicons by the electric field of the positive σ-hole of the F–Cl chlorine. This polarization
may evolve into some degree of dative sharing of electrons by the carbons and silicons. This interpretation is supported by
the fact that complexes of CN–R and SiN–R with Cl–Cl, which has a much weaker positive σ-hole than F–Cl, are considerably
less likely to show the unusual features. It is demonstrated that the full ranges of binding energies of the CN–R and SiN–R
complexes with either F–Cl or Cl–Cl can be represented well (R
2 > 0.96) in terms of the most negative electrostatic potentials and the lowest local ionization energies on the carbon and
silicon surfaces. These properties reflect the electrostatic components of the interactions and the polarizabilities/dative
reactivities of the carbons and silicons. 相似文献
18.
The geometrical structure, binding energy, and vibrational spectra of small clusters of nitrosyl hydride (HNO) and water molecules,
HNO(H2O)
n
, where (n = 1–4), have been investigated at the MP2 level of theory, using 6-311++G(2d,2p) basis set. We located three dimers, six trimers, nine tetramers, and three pentamers at the MP2/6-311++G(2d,2p) computational level. Particular attention is given to existence and magnitude of NH···O blue-shifting hydrogen bonds. Blue
shifts of the NH stretching frequency upon complex formation in the ranges between 28 and 151 cm−1 is predicted. Cooperative effect in terms of stabilization energy along with the many-body interaction energies analysis
was performed for the studied clusters. The Atoms in Molecules (AIM) theory was also applied to explain the nature of the
complexes. 相似文献
19.
O. I. Pokrovskiy K. B. Ustinovich O. I. Usovich O. O. Parenago V. V. Lunin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(8):1602-1608
The optimized geometries and interaction energies of the intermolecular heterodimers of coronene with o-, m-, and p-dimethylbenzenes (xylenes) calculated by DFT in the PBE0 and B97D functionals were compared. The applicability of coronene as a model for qualitative assessment of the interaction of mononuclear aromatic compounds with the graphite surface was demonstrated. The necessity of including long-range dispersion interactions in DFT calculations of the dimerization energies of aromatic systems was shown. The sorption enthalpies of p- and m-xylenes were shown to be almost equal irrespective of the conditions of the chromatographic experiment. The preferred sorption of p- over m-xylene on graphite is solely due to the entropy factor. 相似文献
20.
O. V. Andreeva B. F. Garifullin A. T. Gubaidullin V. A. Al’fonsov V. E. Kataev D. V. Ryzhikov 《Journal of Structural Chemistry》2007,48(3):540-546
Crystalline inclusion complexes of diterpenoid isosteviol (ent-16-ketobeyeran-19-oic acid) with individual benzene, o-, m-, p-xylenes, ethylbenzene, isopropylbenzene, o-and m-nitoranilins, benzaldehyde, styrene and naphthalene are obtained and characterized by single crystal X-ray diffraction. As determined by GC and 1H NMR spectroscopy, isosteviol selectively includes toluene from the equimolar benzene-toluene mixture, o-xylene from a commercial mixture of xylenes, o-and m-nitroanilins from their mixture with p-nitroanilin, and also styrene from styrene-ethylbenzene and styrene-isopropylbenzene mixtures thus yielding crystalline inclusion complexes. 相似文献