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1.
A. V. Belyakov A. A. Baskakov V. N. Naraev A. N. Rykov H. Oberhammer I. Arnason S. O. Wallevik 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(10):1563-1566
The molecular structure of axial and equatorial conformer of the 1-bromo-1-silacyclohexane molecule, CH2(CH2CH2)2SiH-Br, as well as thermodynamic equilibrium between these species are investigated by means of gas-phase electron diffraction and quantum chemistry on the MP2(full)/SDB-AUG-cc-PVTZ level of theory. It is revealed that according to electron diffraction data, the compound exists in the gasphase as a mixture of conformers possessing the chair conformation of the six-membered ring and C s symmetry and differing in the axial and equatorial position of the Si-Br bond (ax. = 80(5) mol %, eq. = 20(7) mol %) at 352 K, that corresponds to the value of A = (G ax ?? ? G eq ?? ) = ?0.82(32) kcal/mol. It is found that observed data agree well with theoretical ones. Using Natural Bond Orbital (NBO) analysis it is revealed that axial conformer of 1-bromo-1-silacyclohexane molecule is an example of the stabilization of the form that is unfavorable from the point of view of steric effects and effects of conjugations. It is concluded that stabilization is achieved due to electrostatic interactions. 相似文献
2.
A. V. Belyakov A. N. Khramov V. N. Naumov 《Russian Journal of General Chemistry》2010,80(11):2249-2258
3.
Alexander V. Belyakov Alexander A. Baskakov Anatolii D. Ivanov Alexander V. Garabadzhiu Ingvar Arnason 《Structural chemistry》2013,24(3):763-768
The molecular structure of the axial and equatorial conformers of fluorocyclohexane and 1-fluoro-1-silacyclohexane, H2C(CH2CH2)2XH–F (X = C or Si), as well as the thermodynamic equilibrium between these species were investigated by means of quantum chemical calculations up to MP2/aug-cc-pVTZ level of theory. According to MP2 data, these compounds consist of a mixture of conformers with chair conformation and C s symmetry differing in the axial and equatorial position of the C–F/Si–F bonds (axial = 42/56 mol%, equatorial = 58/44 mol%) at T = 298 K. This corresponds to a free energy difference of A = (G ax ? G eq) = 0.19/?0.13 kcal mol?1 for X = C/Si. NBO analysis revealed that the axial conformer of 1-fluoro-1-silacyclohexane is an example of stabilization of the form that is unfavorable in terms of conjugation effects; stabilization is achieved mainly due to steric interactions. The equatorial conformer of fluorocyclohexane is an example of stabilization of the form that is unfavorable in terms of electrostatic interactions; stabilization is achieved due to steric and conjugation effects. 相似文献
4.
Jia-xu Zhang Ze-sheng Li Jing-yao Liu Chia-chung Sun 《Theoretical chemistry accounts》2007,117(4):579-586
The radical–molecule reaction mechanism of CH2Cl with NO2 has been explored theoretically at the B3LYP/6–311G(d,p) and MC–QCISD (single-point) levels of theory. Our results indicate that the title reaction proceeds mostly through singlet
pathways, less go through triplet pathways. The initial association between CH2Cl and NO2 is found to be the carbon-to-nitrogen attack forming the adduct a H2ClCNO2 with no barrier, followed by isomerization to b
1
H2ClCONO-trans which can easily convert to b
2
H2ClCONO-cis. Subsequently, the most feasible pathway is the C–Cl and O–N bonds cleavage along with the N–Cl bond formation of b (b
1
, b
2
) leading to product P
1
CH2O + ClNO, which can further dissociate to give P
5
CH2O + Cl + NO. The second competitive pathway is the 1,3-H-shift associated with O–N bond rupture of b
1
to form P
2
CHClO + HNO. Because the intermediates and transition states involved in the above two favorable channels all lie below the
reactants, the CH2Cl+NO2 reaction is expected to be rapid, as is confirmed by experiment. The present results can lead us to understand deeply the
mechanism of the title reaction and may be helpful for further experimental investigation of the reaction. 相似文献
5.
The structures and stability of pentacoordinate germylenoid PhCH2(OH)CH3GeLiF were first theoretically studied by density functional theory. Two equilibrium structures, the three-membered ring (1a) and the p-complex (1b) structures, were located. Their energy are in the order of 1b > 1a. The Ge-O coordination energies at the B3LYP/6-311+G(d, p) level are 13.6 and 0.2 kJ/mol in 1a and 1b, respectively. The insertion reactions with CH3F indicate that germylenoid PhCH2(OH)CH3GeLiF is more stable than germylene PhCH2(OH)CH3Ge. The insertion barrier of 1a with CH3F is only 3.1 kJ/mol higher than that of PhCH3CH3GeLiF, indicating that the oxygen coordination PhCH2(OH)CH3GeLiF has the same stability as PhCH3CH3GeLiF. 相似文献
6.
Polfer NC Dunbar RC Oomens J 《Journal of the American Society for Mass Spectrometry》2007,18(3):512-516
Infrared spectroscopy of gas-phase singly deuterated [Trp+K]+ (formed by H/D exchange with CH3OD) shows that some (∼20%) kinetically stable zwitterionic (ZW) conformer is formed, based on the diagnostic antisymmetric
CO stretch of the deprotonated carboxylate moiety, υas(CO2−), at 1680 cm−1. A majority of the deuterated [Trp+K]+ is found to be in the charge solvation (CS) conformation, with deuterium exchange occurring on both the acid and amino groups,
which is consistent with H/D scrambling. Interestingly, H/D exchange with the more basic ND3 reagent did not result in the stabilization of a kinetically stable zwitterion, although it is not clear yet what causes
this observation. The result for CH3OD shows that H/D exchange can in fact alter the structure of the analyte and, hence, care needs to be taken when interpreting
gas-phase H/D exchange studies. Moreover, this result shows the possibility of forming solution-phase structures that are
thermodynamically disfavored in the gas phase, thus opening a new area of study. 相似文献
7.
Naomi Masuda Yatsuhisa Nagano T. Kimura 《Journal of Thermal Analysis and Calorimetry》2005,81(3):533-535
Summary The standard molar enthalpy of formation of methyl methylthiomethyl sulfoxide, CH3(CH3SCH2)SO, at T=298.15 K in the liquid state was determined to be -199.4±1.5 kJ mol-1 by means of oxygen rotating-bomb combustion calorimetry. 相似文献
8.
In the present work, the detailed reaction mechanism and possible products of the OH-initiated oxidation of CH2=C(CH3)CH2CH2OH (MBO331) have been revealed theoretically for the first time. The potential energy surfaces of various reaction channels
both in the absence and presence of O2 and NO are evaluated at the CCSD(T)/6−31++G(d,p)//MP2(full)/6−311G(d,p)+ZPE*0.95 level. The major products of HCHO + CH3C(O)CH2CH2OH predicted for the title reaction in the presence of O2 and NO are in agreement with those of similar reactions of unsaturated alcohols with OH radical. 相似文献
9.
Jia Cao Wenliang Wang Yue Zhang Weina Wang Tianlei Zhang Jian Lv Chunying Li 《Theoretical chemistry accounts》2011,129(6):771-780
The reaction mechanism of CH3SCH2CH3 with OH radical is studied at the CCSD(T)/6-311+G(3df,p)//MP2/6-31+G(2d,p) level of theory. Three hydrogen abstraction channels,
one substitution process and five addition–elimination channels are identified in the title reaction. The result shows hydrogen
abstraction is dominant. Substitution process and addition–elimination reactions may be negligible because of the high barrier
heights. Enthalpies of formation [
\Updeltaf H(298.15\textK)o \Updelta_{f} H_{(298.15{\text{K}})}^{o} ] of the reactants and products are evaluated at the CBS-QB3, G3 and G3MP2 levels of theory, respectively. It is found that
the calculated enthalpies of formation by the aforementioned three methods are in consistent with the available experimental
data. Rate constants and branching ratios are estimated by means of the conventional transition state theory with the Wigner
tunneling correction over the temperature range of 200–900 K. The calculation shows that the formations of P1 (CH2SCH2CH3 + H2O) and P2 (CH3SCHCH3 + H2O) are major products during 200–900 K. The three-parameter expressions for the total rate constant is fitted to be
k\texttotal = 1.45 ×10 - 21 T3.24 exp( - 1384.54/T) k_{\text{total}} = 1.45 \times 10^{ - 21} T^{3.24} \exp ( - 1384.54/T) cm3 molecule−1 s−1 from 200 to 900 K. 相似文献
10.
L. B. Serezhkina E. V. Mit'kovskaya I. V. Medrish E. V. Grechishnikova F. M. Dolgushin M. Yu. Antipin V. N. Serezhkin 《Russian Journal of Coordination Chemistry》2005,31(12):889-893
The single crystals of [UO2SO4{(CH3)HNCONH(CH3)}2] (I) were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 6.847(1) Å, b = 14.259(3) Å, c = 14.297(3) Å, β = 93.451(4)°, space group P21/n, Z = 4. The main structural units of crystals I are ribbons whose composition coincides with the composition of the compound. The crystal chemical formula of the complex is AT3M 2 1 (A = UO 2 2+ ). 相似文献
11.
Fabio Carniato Andrea Secco Giorgio Gatti Leonardo Marchese Enrico Sappa 《Journal of Sol-Gel Science and Technology》2009,52(2):235-241
The reaction of Ru3(CO)12 with 2(diphenylphosphino)ethyl-triethoxysilane (DPTS) in hydrocarbons, leads to the functionalized Ru3(CO)12−n
[Ph2P(CH2)2Si(OEt3)]
n
(n = 1,2) complexes. The complex with two phosphine substituents was chemically anchored on mesoporous silicas, SBA-15 and MCM-41,
in order to obtain two hybrid materials characterized by a different localization of the metal centre on the surface of the
porous supports. A detailed investigation of the cluster, before and after chemical anchoring on the mesoporous silicas, was
pursued. Particular attention was also devoted to the study of the morphological, structural and textural properties of the
metal-functionalised silicas (Ru/SBA-15 and Ru/MCM-41) by infrared spectroscopy (FT-IR), scanning electron microscopy, X-ray
diffraction and N2 physisorption analysis. 相似文献
12.
Yang Ding Liguo Song Li Yao Wenwen Xia 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(13):2548-2557
In this paper, using the B3LYP functional and CCSD(T) method with 6-311++G** basis set, the harmonic and anharmonic rate constants in the unimolecular dissociation of ethyl propanoate have been calculated using Rice–Ramsperger–Kassel–Marcus theory. The anharmonic rate constants of the title reaction have also been examined, the comparison shows that, the anharmonic effect especially in the case of high total energies and temperature for channels 3 to 6 is significant, so that the anharmonic effect cannot be neglected for unimolecular dissociation reaction of CH3CH2C(=O)OCH2CH3 both in microcanonical and canonical systems. 相似文献
13.
M. Yu. Shilova A. V. Vologzhanina L. B. Serezhkina S. A. Novikov V. N. Serezhkin 《Russian Journal of Inorganic Chemistry》2011,56(10):1555-1560
A new complex [UO2CrO4{CH3CON(CH3)2}2] (I) was studied by thermal analysis, IR spectroscopy, and X-ray crystallography. The crystals are monoclinic: a = 13.8108(11) Å, b = 8.6804(7) Å, c = 13.0989(10) Å, β = 104.777(1)°, V = 1518.4(2) Å3, space group P21/c, Z = 4, R = 2.39%. The structure of I contains infinite chains of the [UO2CrO4{CH3CON(CH3)2}2] composition running along [001]; the complex belongs to the AT11M1 2 crystal-chemical group (A = UO 2 2+ , T11 = CrO 4 2? , M1 = CH3CON(CH3)2) of uranyl complexes. The chains are linked into a three-dimensional framework due to hydrogen bonds between oxygen atoms of chromate ions and hydrogen atoms of methyl groups of the dimethylacetamide. 相似文献
14.
O. B. Bondarenko A. Yu. Gavrilova V. N. Tikhanushkina N. V. Zyk 《Russian Chemical Bulletin》2005,54(9):2145-2149
Study of the reactions of compounds of the norbornene series demonstrated that the AgNO2-SOCl2 and AgNO3-SOCl2 systems serve as nitrosochlorinating agents under the conditions of electrophilic addition. X-ray diffraction study showed
that dimerization of cis-exo-2-chloro-3-nitrosobicyclo[2.2.1]heptane occurs heterostereospecifically. The origin of the active principle of the reagents
is discussed.
For Part 1, see Ref. 1.
Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2081–2085, September, 2005. 相似文献
15.
The quantum-chemical calculations of the (C6H5)2PCl3 molecule were performed by the methods RHF/6-31G(d) and MP2/6-31G(d) with complete and partial optimization of its geometry. The results of calculations were used for evaluating the NQR frequencies of 35Cl and the parameters of asymmetry of the of electric field gradient on the 35Cl nuclei of this molecule. According to the results of calculations with the partial optimization of geometry and to the experimental data of 35Cl NQR the bond lengths were found of central atom P in the solid state of this compound. The mutual influence of its axial and equatorial bonds was studied. It is shown that in chlorophosphoranes the 35Cl NQR frequencies of the axial and equatorial chlorine atoms decrease with the decrease in the bond lengths of phosphorus atom. 相似文献
16.
One new metal – organic coordination framework formulated as [{Cu(4,4′-bipy)(CH3COO)2}·3H2O]n (1) (where 4,4′-bipy=4,4′-bipyridine) has been hydrothermally synthesised and characterised by elemental analysis, IR and electronic
spectroscopy, variable temperature magnetic moment measurement and single crystal X-ray diffraction study. Single crystal
X-ray analysis reveals that 1 is one dimensional polymeric compound in which acetate ligand shows both mono- and bidentate bonding mode, and 4,4′-bipy
acts as bridging ligand which supports the formation of infinite chains. The global feature of the χ
M
T vs. T curve in 1 is characteristic of moderate antiferromagnetic interaction and the best fit parameters from 300 down to 2 K are found as
J = −78.7 cm−1. 相似文献
17.
N. I. Giricheva G. V. Girichev N. P. Kuzmina Yu. S. Medvedeva A. Yu. Rogachev 《Journal of Structural Chemistry》2009,50(1):52-59
In the framework of synchronous gas-phase electron diffraction and mass spectrometry experiment, the saturated vapor of N,N′-ethylenebis(salicylaldiminate) copper(II) CuO2N2C16H14 is studied at a temperature T 574(5) K. It is found that evaporation is congruent and the saturated vapor consists of monomeric molecules. Electron diffraction data are proved to correspond to the geometric model for the CuO2N2C16H14 molecule of C 2 symmetry with an almost planar structure of the CuN2O2 coordination fragment and internuclear distances \(r_{h_1 } \)(Cu-O) = 1.917(13) Å and \(r_{h_1 } \)(Cu-N) = 1.931(15) Å. The stuctural parameters obtained are compared to those quantum chemically calculated and molecular parameters in crystals. 相似文献
18.
The structures of pentacoordinate silylenoid PhCH2(NH2)CH3SiLiF were studied by density functional theory at the B3LYP/6-31G(d) level. Three equilibrium structures, the three-membered
ring (1), the p-complex (2), and the σ-complex (3) structures, were located. Their energies are in the order of 2 > 1 > 3 both in vacuum and in THF. To exploit the stability of PhCH2(NH2)CH3SiLiF, the insertion reactions of 1 and PhCH2(NH2)CH3Si into C–F have been investigated, respectively. The results show that the insertion of PhCH2(NH2)CH3Si is more favorable. To probe the influence of amine-coordination to the stability of PhCH2(NH2)CH3SiLiF, the insertion reaction of PhCH3CH3SiLiF was also investigated. The calculations indicate that the insertion of PhCH3CH3SiLiF is more favorable than that of 1. So the N atom plays an important role on the stability of silylenoid PhCH2(NH2)CH3SiLiF. 相似文献
19.
I. B. Baranovskii M. D. Surazhskaya G. G. Aleksandrov 《Russian Journal of Inorganic Chemistry》2009,54(3):381-384
Heating of a hydrochloric acid solution of trans-PtPy(NH2CH2CN)Cl4 results in the hydrolysis of coordinated aminoacetonitrile to aminoacetic acid with the formation of a five-membered chelate ring attached to platinum through the nitrogen atom of the amino group and the oxygen atom of the carboxy group. X-ray diffraction analysis of [PtPy(NH2CH2COO)Cl3] is carried out. The crystals are monoclinic: space group C2/c, a = 21.704(2), b = 8.7027(7), c = 15.576(1) Å, β = 126.606(1)o, V = 2361.8(3) Å3, Z = 8; R hkl = 0.057, wR = 0.141. In the neutral complex, the Pt atom has a distorted octahedral coordination. The equatorial plane is formed by a Cl atom (Pt-Cl, 2.284(3) Å), the N atom of the Py molecule (Pt-N, 2.062(8) Å), and the N and O atoms of the bidentate-chelating ligand (Pt-N, 2.039(8); Pt-O, 2.026(7) Å); two Cl atoms are arranged in the apical positions (Pt-Cl, 2.301(3) and 2.312(3) Å). The five-membered chelate ring has a flattened gauche conformation with an NCCO torsion angle of 19(1)°. 相似文献
20.
M. Yu. Shilova A. V. Vologzhanina L. B. Serezhkina V. N. Serezhkin 《Russian Journal of Coordination Chemistry》2009,35(2):153-156
The single crystals of [UO2(C2O4){CONH2N(CH3)2}2] were synthesized and studied by X-ray diffraction. The crystals are monoclinic, a = 7.461(2) Å, b = 8.828(2) Å, c = 11.756(2) Å, β = 107.21(3)°, space group Pc, Z = 2, R = 2.94%. The structure comprises infinite chains [UO2(C2O4){CONH2N(CH3)2}2] extended along [001] and corresponding to the AT11M 2 1 crystallochemical group (A = UO 2 2+ , T11 = C2O 4 2? , M1 = N,N-CONH2N(CH3)2) of uranyl complexes. The chains are connected into a three-dimensional framework by hydrogen bonds involving the oxygen atoms of oxalate and uranyl ions and the N,N-dimethylcarbamide methyl groups. 相似文献