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1.
I. G. Zenkevich 《Fresenius' Journal of Analytical Chemistry》1999,365(4):305-309
New methods for the precalculation of GC retention indices (RIs) are discussed. The first is based on a new modification
of the correlation equation log RI = a logTb + bA + c and is recommended for low boiling compounds of the general type R-X with known boiling points (Tb) analyzed on polymer sorbent Porapack Q. The second method permits one to predict RIs of products of organic reactions A
+ B → C +… with the correlation ΔRI = a ΔE + b (a < 0,|ρ| > 0.9), where ΔRI = RIC– RIA– RIB and ΔE = EC– EA– EB– are the differences in the internal molecular energies of reagents and products of organic reactions which are estimated
by molecular dynamics methods. In the final section new possibilities of the use of RIs in reversed phase HPLC, namely for
the determination of the number of hydroxyl groups in phenols, are illustrated.
Received: 9 November 1998 / Revised: 15 April 1999 / Accepted: 30 April 1999 相似文献
2.
I. G. Zenkevich E. V. Eliseenkov A. N. Kasatochkin Z. A. Zhakovskaya L. O. Khoroshko 《Journal of Analytical Chemistry》2011,66(4):396-406
The differences in the gas chromatographic retention indices of the chlorination products of aliphatic ketones and parent
carbonyl compounds (ΔRI) are constant, and their numeric values depend on the number and position of chlorine atoms in the
molecule. A simplest version of an additive scheme for the evaluation of retention indexes is developed to identify the chloro
derivatives of carbonyl compounds. The order of the chromatographic elution of diastereomeric α,α′-dichloro-k-alkanones (k > 2) is found. 相似文献
3.
Summary The retention indices of cycloalkenes and cycloalkadienes with C6–C13 rings are determined by gas-liquid chromatography (GLC) on glass capillary columns coated with OV-1 and Ucon LB 550X and
by gas-solid chromatography (GSC) on a microcolumn packed with uncoated graphitized thermal carbon black (GTCB). Structure
— retention correlations are derived on using index differences such as HOV, HGTCB and ΔI values, considering the differences in the stereochemistry of these compounds. It is shown that the combined application
of index increments obtained in GLC and GSC provides more detailed structure informations. The value of the retention index
units agree with the most stable conformations of the alicyclic compounds.
The high value for the energy equivalent to an index unit (ΔGI.U.=4.18kJ/mol) confirmes that graphitized thermal carbon black causes much stronger dispersive interactions than any nonpolar
liquid phase.
Dedicated to Prof. Dr. E. sz. Kováts (Ecola Polytechnique Fédérale de Lausanne) on the occasion of his sixtieth birthday. 相似文献
4.
Summary The analysis of α, β, γ, δ-tocopherols, trienols, α-tocopheryl acetate and nicotinate (vitamin E) in complex matrices was
carried out using a new liquid chromatographic (HPLC) method giving better separation efficiency, selectivity and sensitivity
than that described in the literature. The use of normal-phase (NP)-HPLC on silica gel with issoctane-diisopropylether-1,4-dioxane
as optimized mobilepphase yielded higher resolution than conventional reversed-phase (RP)-HPLC using methanol mobile phase.
Identification of peaks was by UV-absorbance at 295 nm, diode array, or fluorescence detection (λ
ex = 295 nm,λ
ex = 330 nm). The latter was found to be more selective and ten times more sensitive than UV-absorbance detection. A quadrupole,
ion-trap mass spectrometer with an atmospheric-pressure ionization (APCl) interface was used to detect vitamin E constituents
in the femtomole range. With collision-induced dissociation (CID) in the ion source, which gave characteristic fragmentation,
the identity of the investigated compounds could be confirmed. Plots of peak area versus amount injected allowed quantitation
of α, β, γ, δ-tocopherols and-trienols, α-tocopheryl acetate and nicotinate in real samples such as peanut, almond, spinach,
spelt grain bran, latex and tablets. The method described offers fast identification and quantitation of vitamin E constituents
of complex biological origin.
Dedicated to Professor Dr. Heinz Engelhardt on the occasion of his 65th birthday. 相似文献
5.
A. A. Isaeva A. I. Baranov Th. Doert M. Ruck V. A. Kulbachinskii R. A. Lunin B. A. Popovkin 《Russian Chemical Bulletin》2007,56(9):1694-1700
New metal-rich mixed nickel-silicon and nickel-germanium chalcogenides, Ni5.68SiSe2, Ni5.46GeSe2, and Ni5.42GeTe2, were synthesized by high-temperature ceramic techniques. The X-ray diffraction study of single crystals grown from a molten
flux revealed that the compounds are isostructural and crystallize in the tetragonal system (space group I4/mmm, Z = 2). These compounds are the first members of the family of M7−δEX2-type (M = Ni or Pd; E = Sn or Sb; X is chalcogen) intergrowth structures containing “light” p elements E. Resistivity measurements on pressed textured pellets showed that both selenides are anisotropic metallic conductors
in the directions parallel and perpendicular to the heterometallic bond systems. The geometric criteria of stability of the
intergrowth structure type under consideration are discussed.
Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1632–1638, September, 2007. 相似文献
6.
V. N. Emel’yanenko S. P. Verevkin E. N. Burakova G. N. Roganov M. K. Georgieva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(8):1271-1279
The enthalpies of formation of δ-hexanolactone and δ-nonanolactone were determined by combustion calorimetry. Conformational
analysis and quantum-chemical calculations of equilibrium structures, fundamental vibrations, moments of inertia, and total
energies were performed for δ-pentanolactone (I), δ-hexanolactone (II), and δ-nonanolactone (III) by the B3LYP/6-311G(d,p), B3LYP/6-311++G(d,p), and G3MP2 methods. The experimental IR spectra and calculated vibrational frequencies were used to suggest the assignment
of vibrational frequencies of stable conformations. The thermodynamic properties of I–III in the ideal gas state were determined over the temperature range 0–1500 K. A thermodynamic analysis of mutual isomerization
in the gas and liquid phases over the temperature range 298.15–900 K and liquid-phase polymerization of γ- and δ-pentanolactones
and 4-pentenoic acid over the temperature range 298.15–500 K was performed. 相似文献
7.
8.
The retention indices of five- and six-membered nitrogen-containing heterocyclic compounds (pyrrole, pyrazole, imidazole,
1,2,4-triazole, pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, isoxazole, and oxazole) were determined on a capillary
column with the OV-101 nonpolar stationary phase. The difference between the experimentally determined boiling point of the
sorbate and that calculated from GC data (δT
b.p.) was proposed as a gas chromatographic indicator sensitive to the ability of substances to form self-associates in pure liquids.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 730–733, April, 1999. 相似文献
9.
Jordi Poater Miquel Solà Miquel Duran Xavier Fradera 《Theoretical chemistry accounts》2002,107(6):362-371
Localization, λ(A), and delocalization indices, δ(A,B), as defined in the atoms in molecules theory, are a convenient tool for the analysis of molecular electronic structure from
an electron-pair perspective. These indices can be calculated at any level of theory, provided that first- and second-order
electron densities are available. In particular, calculations at the Hartree–Fock (HF) and configuration interaction (CI)
levels have been previously reported for many molecules. However, λ(A) and δ(A,B) cannot be calculated exactly in the framework of Kohn–Sham (KS) density functional theory (DFT), where the electron-pair
density is not defined. As a practical workaround, one can derive a HF-like electron-pair density from the KS orbitals and
calculate approximate localization and delocalization indices at the DFT level. Recently, several calculations using this
approach have been reported. Here we present HF, CI and approximate DFT calculations of λ(A) and δ(A,B) values for a number of molecules. Furthermore, we also perform approximate CI calculations using the HF formalism to obtain
the electron-pair density. In general, the approximate DFT and CI results are closer to the HF results than to the CI ones.
Indeed, the approximate calculations take into account Coulomb electron correlation effects on the first-order electron density
but not on the electron-pair density. In summary, approximate DFT and CI localization and delocalization indices are easy
to calculate and can be useful in the analysis of molecular electronic structure; however, one should take into account that
this approximation increases systematically the delocalization between covalently bonded atoms, with respect to the exact
CI results.
Received: 13 February 2002 / Accepted: 24 April 2002 / Published online: 18 June 2002 相似文献
10.
Julius Tsuwi Dietmar Appelhans Stefan Zschoche Rong-Chuan Zhuang Peter Friedel Liane Häußler Brigitte Voit Friedrich Kremer 《Colloid and polymer science》2005,283(12):1321-1333
A series of alternating maleimide (MI) copolymers with fluorinated side chains have been investigated using broadband dielectric
spectroscopy. The side chains consist of fluoroalkane (–C
x
F2x+1, x=1, 7, 9) end groups connected to the main chain via methylene spacers. The experiments were carried out in a frequency range
of 0.1 Hz to 10 MHz and at temperatures between 120 K and 500 K. The fluorinated MI copolymers show a fast sub-T
g (β) relaxation characterized by an Arrhenius-type temperature dependence with activation energy in the range of 30–37 kJ/mol.
Two more processes (α and δ-like) are observed, corresponding to independent relaxations of the main chain and the fluoroalkane
domains respectively. For shorter side chains, the δ-like process is not observed but instead another relaxation process,
α
S
, occurs at temperatures higher than either the α and δ-like processes. When compared with unfluorinated MI copolymers, the
fluorinated MI copolymers show the δ-like process and a slower β-relaxation unlike their unfluorinated counterparts. A model
to explain the molecular origin of the four processes is proposed, supplemented by differential scanning calorimetry and published
WAXS/SAXS data. 相似文献
11.
I. G. Zenkevich 《Analytical and bioanalytical chemistry》1999,365(4):305-309
New methods for the precalculation of GC retention indices (RIs) are discussed. The first is based on a new modification of the correlation equation log RI = a logTb + bA + c and is recommended for low boiling compounds of the general type R-X with known boiling points (Tb) analyzed on polymer sorbent Porapack Q. The second method permits one to predict RIs of products of organic reactions A + B → C +… with the correlation ΔRI = a ΔE + b (a < 0,|ρ| > 0.9), where ΔRI = RIC– RIA– RIB and ΔE = EC– EA– EB– are the differences in the internal molecular energies of reagents and products of organic reactions which are estimated by molecular dynamics methods. In the final section new possibilities of the use of RIs in reversed phase HPLC, namely for the determination of the number of hydroxyl groups in phenols, are illustrated. 相似文献
12.
S. P. Gabuda S. G. Kozlova V. M. Paasonen A. S. Nazarov 《Journal of Structural Chemistry》2000,41(1):67-71
In Inclusion compounds of fluorinated graphite with chlorine trifluoride C2. xClF3 and hexafluoro-benzene C2F. xC6F6 , the guest molecules are characterized by rotational mobility and weak bonds with the host matrix. 19F NMR chemical shift tensors are determined for the fluorine nuclei of the matrix and the guest molecules, including the structurally
nonequivalent fluorine atoms ofClFj molecules [δ (Fl) = −700, δ(F1) = −280; δ|| (F2) = −440, δ±(F2) = −220ppm relative to F2]. It is shown that C-F bonds in the host matrix are close to those in aromatic fluorocarbons.
Translated from Zhumal Stmktumoi Khimii, Vol. 41, No. 1, pp. 80-85, January–February, 2000. 相似文献
13.
L. A. Glinskaya T. G. Leonova T. E. Kokina R. F. Klevtsova S. V. Larionov 《Journal of Structural Chemistry》2005,46(4):692-698
Crystal structures of chelate compounds Ni[(iso-C4H9)2PS2]2 (I) and Pd[(iso-C4H9)2PS2]2 (II) have been determined by X-ray diffraction: diffractometer X8-APEX, MoK
α∔
-radiation, 1048 F
hkl
, R = 0.0544 for I and CAD-4 diffractometer, MoK
α∔
-radiation, 1283 F
hkl
, R = 0.0347 for II. The crystals are rhombic: a = 12.921(5) Å, b = 17.094(5) Å, c = 22.971(5) Å; V = 5074(3) Å3, Z = 8, calc = 1.250 g/cm3, space group Pbca for I and a = 13.312(3) Å, b = 16.130(7) Å, c = 23.171(5) Å; V = 4975(3) Å3, Z = 8, ρcalc = 1. 208 g/cm3, space group Pbca for II. The structures of I and II are formed by discrete mononuclear molecules. Coordination cores MS4 (M = Ni, Pd) approach planar square configurations.
Original Russian Text Copyright ? 2005 by L. A. Glinskaya, T. G. Leonova, T. E. Kokina, R. F. Klevtsova, and S. V. Larionov
__________
Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 4, pp. 715–720, July–August, 2005. 相似文献
14.
I. E. Smirnova E. V. Tret’yakova O. B. Kazakova Z. A. Starikova 《Journal of Structural Chemistry》2009,50(2):381-383
Synthesis is performed and the molecular structure is analyzed of methyl-4-anti-hydroxyimino-1-dioxolano-13-isopropyl-10a,7-dimethylpentacyclo[10b.8.5.04b,10b.06a,10a.01a,4a]icos-14-ene-7-carboxylate IIa. Compound IIa C27H40O4 crystallizes in monoclinic symmetry with cell parameters: a = 13.785(13) ?, b = 7.302(7) ?, c = 13.817(13) ?, β = 94.799(19)°, space group P2(1), Z = 2, d = 1.164 g/cm3.
Original Russian Text Copyright ? 2009 by I. E. Smirnova, E. V. Tret’yakova, O. B. Kazakova, and Z. A. Starikova
__________
Translated from Zhurnal Strukturnoi Khimii, Vol. 50, No. 2, pp. 393–395, March–April, 2009. 相似文献
15.
T. A. Rodina A. V. Ivanov V. A. Konfederatov V. I. Mitrofanova A. V. Gerasimenko O. N. Antzutkin 《Russian Journal of Inorganic Chemistry》2009,54(11):1779-1788
Two crystalline modifications (Ia and Ib) of the polynuclear thallium (I) O,O′-dicyclohexyl phosphorodithioate complex [Tl{S2P(O-cyclo-C6H11)2}]
n
have been synthesized and characterized by CP/MAS NMR (13C, 31P). From full 31P CP/MAS NMR spectra, the χ2 plots were constructed to calculate the 31P chemical shift anisotropy 31P − δaniso = (δzz − δiso) and asymmetry parameters η = (δ
yy
− δ
xx
)/(δ
zz
− δiso). The data obtained for the O,O′-dicyclohexyl phosphorodithioate (Dtph) groups (in both modifications) are evidence that the 31P chemical shift tensors are intermediate between rhombic and axially symmetric. However, whereas the rhombic component dominates
for Ia, the tensor for Ib is close to axially symmetric (for δ
zz
< δ
yy
≈ δ
xx
). The same pattern of the MAS spectra corresponding to negative δaniso (δ
zz
< δ
yy
< δ
xx
) points to a bridging or terminal/bridging coordination mode of the Dtph groups. X-ray crystallography shows that complex
Ib has a polynuclear structure (of the chain polymer type). The chains are composed of alternating structurally nonequivalent
noncentrosymmetric binuclear molecules [Tl2{S2P(O-cyclo-C6H11)2}2]. All Dtph ligands have the terminal/μ3-bridging coordination mode. 相似文献
16.
The IR and electronic absorption spectra of molten mixtures in the NaCl-CsCl-NaF-CoCl2, NaCl-KCl-NaF-CoCl2, and NaCl-KCl-NaKCO3-CoCl2 systems have been studied. The spectral data show that, for all molten mixtures, the composition ranges exist in which chloro
fluoro Co(Cl
n
F
m
)(n + m = 4–6) and carbonato chloro CoCl(CO3)4 − n
(n = 1–3) complex groups are formed at δ1 < δ1* and δ2 < δ2* (δ1* = F/Co and δ2* = CO3/Co). At δ1 ≥ δ1* and δ2 ≥ δ2*, the mixtures contain complexes homoligand Co and CoF64− and Co(CO3)46−. 相似文献
17.
S. P. Gabuda S. G. Kozlova D. N. Dybtsev V. P. Fedin 《Journal of Structural Chemistry》2009,50(5):887-894
By the 1H NMR and Raman spectroscopy data it is shown that in the porous inclusion compound of Zn2(C8H4O4)2[(N2(CH2)6))]·n(CH3)2CO (n ≈ 0–4.7) acetone molecules exist in two structural forms: ketonic (CH3)2CO, for which the 1H NMR chemical shift value is δket = 0.8 ppm, and enolic CH3C(O)=CH2, for which δen(OH) = 11 ppm, δen(CH2) = 8.9 ppm, and δen(CH3) = 1.6 ppm are found, the average value over three proton sites being <δen> = 5.6 ppm. A sharp difference in chemical shift values for the keto and enol forms of acetone in the inclusion compounds
can be assigned to the effect of structural chemical conditions in two types of adsorption centers. 相似文献
18.
A series of aromatic vinyl ethers and some compounds close to them in structure are studied by DFT (B3LYP/6-311+G(2d,p)) and MP2(full)/6-311+G(2d,p) methods. Measurements of Raman spectra are also used. The calculation of vibrational spectra of aryl vinyl ether (AVE) isomers
shows that stretching vibrations ν(C=C) are most conformation sensitive. The calculated value of I(C=C) for vinyl phenyl ether more than twice exceeds the corresponding value for vinyl methyl ether. The calculated and experimental
values of I(C=C) are consistent with the hypothesis about the presence of a common conjugated π-system in the molecules of substituted
AVEs. Here the bridging oxygen atom provides the π,p,π-interaction. 相似文献
19.
Retention indices of cymene isomers published in popular GC—MS atlases were found to be erroneous by analyzing synthetic samples.
The following retention indices (RI) were found using a nonpolar phase (diphenyl: dimethylpolysiloxane, 5:95) for four essential-oil
components with indistinguishable mass spectra: 3,7,7-trimethylcyclohepta-1,3,5-triene (RI = 970), m-cymene (RI = 1022), p-cymene (RI = 1024), and o-cymene (RI = 1039). The relative distributions of these compounds were evaluated based on the analysis of about 1000 essential
oils. Simple methods were given for preparing standard mixtures of isomeric compounds for identification by GC—MS.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 569–571, November–December, 2006. 相似文献
20.
The values of the gas-chromatographic indicator reflecting the capacity of analytes for self-association in pure liquids,
δT
b.p., were estimated for C1–C9 and C11
n-alkanols by capillary gas chromatography on a nonpolar stationary phase under isothermal conditions. The δT
b.p. values ofn-alkanols, found as the difference between the boiling points measured directly and those calculated from GC data, are correlated
with thermodynamic characteristics of the formation ofn-alkanol associates in pure liquids. Usingn-alkanols as analytes with insignificant temperature increments of the retention indices, it was shown that the δT
b.p. values can be determined under conditions used in gas chromatography with temperature programming. In this way a single chromatographic
run can be used to compare the capacities for self-association of analytes boiling over a wide temperature range. The C2–C9
n-alkanethiols, which are not associated in neat liquids, have negative δT
b.p. values. An interpretation of this finding is proposed.
Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 315–318 February, 2000. 相似文献