Forming taxonomic groups of organic compounds for calculating gas-chromatographic retention indices from physicochemical constants

The traditional approach to calculations of gas-chromatographic retention indices from physicochemical constants of organic compounds in homologous series does not encompass all possible objects. Forming different taxonomic groups of compounds by variations in the formal unsaturation, the number of atoms of different elements within molecules, or any complex fragments of structure/composition makes it possible to calculate unknown retention indices by several independent methods from different arrays of initial data. The application of simple three-parameter equations provides an accuracy comparable to the modern interlaboratory error of determination of retention indices for any compounds. St. Petersburg State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 6, pp. 176–182, November–December, 1994. Translated by L. Smolina     

Identification by GC—MS of cymene isomers and 3,7,7-trimethylcyclohepta-1,3,5-triene in essential oils

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.     

Use of molecular connectivity indices to predict LC retention of dansylamides in six different eluent systems

Summary Molecular connectivity indices (x) through the sixth order were calculated and compared with measured reversed-phase liquid chromatographic retention data of sixteen dansyl derivatives of amines (dansylamides). Retention measurements were performed in the capacity factor, k′, range 1–30 with organic solvent-water eluents using acetone, acetonitrile, ethanol, methanol, 1-propanol and 2-propanol. Mainly valence level indices were selected to describe retention. Indices of different order were selected in the different eluents, suggesting that there are differences in the retention mechanism in these eluents. Retention can be predicted with great accuracy by the molecular connectivity indices, as the high correlations between the calculated and observed retention indicate. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Structure and properties of organic molecules. 2. Graph-theoretical study of alkenes and alcohols

Topological indices for describing organic compounds with multiple bonds and heteroatoms are treated. The Schultz indices (including modified ones) and the connectivity indices of various types are calculated for saturated alkenes and alcohols. The discriminating ability of the indices and their applicability for structure-property correlations are examined. Various functions approximating the property-index correlations are tested using regression analysis. The Schultz and connectivity indices possess nearly the same correlation ability, as shown by reference to formation enthalpy, molar volume, evaporation heat, and boiling temperature. They may be effectively used for calculating and predicting the physicochemical properties of the title compounds. Tver State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 3, pp. 493–499, May–June, 1998. This work was supported by RFFR grant No. 96-03-32384.     

Alkaloids from <Emphasis Type="Italic">Nitraria schoberi</Emphasis>. O-acetylnitraraine

The new alkaloid O-acetylnitraraine was isolated from the aerial part of Nitraria schoberi. Its structure was established using spectral data and chemical transformations. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 472–473, September–October, 2005.     

Mutual correlation between gas chromatographic retention indices of unsaturated and saturated hydrocarbons found by molecular dynamics

It is shown that gas Chromatographic retention indices for cycloalkenes can be calculated from the corresponding data for cycloalkanes (and vice versa) using computer simulation of intramolecular vibrational and rotational processes by molecular dynamics. For organic compounds structurally related asA → B, the total internal energy differences δE = E(B)-E(A) correlate with the corresponding differences in retention indices δI = I(B)-I(A), and a linear relationship exists δI =aδE + b (a < 0, |ρ| > 0.9). Limitations are found for the use of molecular dynamics for compounds havingn-alkyl radicals with no less than four carbon atoms. In these cases, a simpler model for the evaluation of dynamic molecular parameters should be preferred for the calculation of retention indices of acyclic alkenes and alkanes. The reliability of the retention indices evaluated by the proposed technique is comparable to their interlaboratory reproducibility found using standard nonpolar poly(dimethylsiloxane) stationary phases.     

Chain numbering and encoding of cyclic hydrocarbons

The numbering of carbon atoms in organic molecules is called chain numbering. It is suggested that bonds be classified as chain bonds (between atoms with consecutive indices) and nonchain bonds. Among atoms we distinguish the first atom (No. 1) and the last atom (having the largest index) as well as initial and final atoms (starting and finishing unbranched sections of atomic chains). Also, internal numbering of elements within these classes is proposed. For condensed cyclic hydrocarbons, formulas for deriving the number of cycles are given, and a linear-chain encoding system is worked out; in this system, nonchain bonds are assigned the indices of their atoms. Rules for unique numbering (canonical chain numbering) are developed; they involve maximization of the indices of the initial atoms and nonchain bonds. The linear-chain encoding of cyclic hydrocarbon structures ensures unification and systematization of their names. Tambov State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 4, pp. 731–736, July–August, 1995. Translated by L. Smolina     

High-temperature crystal chemistry of normal paraffins with even numbers of carbon atoms

Thermal deformations and phase transformations of evennumbered paraffins C_nH_2n+2(n=20, 22, and 24) have been investigated in a thermal X-ray diffraction study. In homologs with n=20 and 24, phase transformations occur in two steps: triclinic-to-orthorhombic and orthorhombic-to-hexagonal transitions. An orthorhombic rotator phase of even n-paraffins is described for the first time. A crystal-chemical model of the phase transformations of the homologs is suggested. St. Petersburg State University. Translated fromZhurnal Strukturmoi Khimii, Vol. 36, No. 5, pp. 790–798, September–October, 1995. Translated by L. Smolina     

Lavandoside from <Emphasis Type="Italic">Lavandula spica</Emphasis> flowers

The new natural compound lavandoside with the structure ferulic acid 4-O-β-D-glucopyranoside was isolated by column chromatography over silica gel and polyamide from the extract of Lavandula spica flowers. The chemical structure of lavandoside was established using UV, NMR, and mass spectra and chemical transformations. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 133–134, March–April, 2008.     

Cyclochivinoside B from the aerial part of <Emphasis Type="Italic">Astragalus chivensis</Emphasis>

The known glycoside aleksandroside I and the new cycloartane glycoside cyclochivinoside B, 24S-cycloartan-3β,6α,16β,24,25-pentaol 3,25-di-O-β-D-glucopyranoside, were isolated from the aerial part of Astragalus chivensis. Their structures were established using chemical transformations and two-dimensional spectra (TOCSY, ROESY, HMBC, HSQC, COSY). __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 138–140, March–April, 2007.     

Gas-liquid chromatography of thioesters of perfluorocarboxylic acids 1. Characteristics of retention

Retention of thioesters of perfluoropentanoic acid C₄F₉C(O)SR was studied by GLC on packed and capillary columns using stationary phases SE-30, SKTFT-50X, XE-60, and Carbowax 20M. The retention indices of these compounds were calculated, and their relationship with the structure of the compounds and the conditions of the analysis were established. Translated fromIzvestiya Akademii, Nauk. Seriya Khimicheskaya, No. 5, pp. 984–986, May, 1997.     

Two new isoflavonoid monogalactosides from <Emphasis Type="Italic">Trifolium pratense</Emphasis> roots

Formononetin and the new isoflavonoid glycosides formononetin-7-O-β-D-galactopyranoside and inermin-3-O-β-D-galactopyranoside were isolated from Trifolium pratense L. roots. The structures of the isolated compounds were proved using chemical transformations and UV, PMR, and ¹³C NMR spectra. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 21–23, January–February, 2008.     

Topological analysis of the structure-mesomorphous property ralationship

The use of topological indices to reveal the relationship between molecular structure and mesomorphous properties is discussed. Mathematical models for classification of mesophase types are proposed. The effect of molecular structure and attractive ability on phase transition temperatures is described. Examples of using correlation equations to predict the properties of 2,5-disubstituted 1,3-dioxanes are given. A. V. Bogatskii Physicochemical Institute, Ukrainian Academy of Sciences. Translated fromZhurnal Struktumoi Khimii, Vol. 35, No. 4, pp. 53–60, July–August, 1994. Translated by L. Smolina     

An equation for the calculation of retention indices in temperature-programmed gas chromatography with allowance for the nonlinear variation of the retention parameters ofn-alkanes

In view of the nonlinear variation of the temperature increments ofn-alkanes found previously, the accuracy of the calculations of the retention indices (I _pr) of substances in temperature-programmed capillary gas chromatography carried out in terms of six known equations was verified. A new four-parameter equation was proposed, and a general method for the calculation of its coefficients, suitable for all stationary phases, based on the adjusted retention times ofn-alkanes was suggested. The coefficients of the equation for 12 temperature variation programs were determined. Using the homologous series of methyl esters of fatty acids as an example, it was shown that the proposed equation ensures the minimum error of determination ofI _pr under various conditions. The equation also makes it possible to carry out interpolation and extrapolation calculations. The coefficients of the equation are found using the least-squares method based on data for any 4–5 referencen-alkanes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 323–327, February, 1997.     

Two approaches to the synthesis of 9-oxo-and 10-hydroxy-2<Emphasis Type="Italic">E</Emphasis>-decenoic acids,important components of queen substance and royal jelly of honeybees <Emphasis Type="Italic">Apis mellifera</Emphasis>

Two approaches to the synthesis of 9-oxo-and 10-hydroxy-2E-decenoic acids, biologically active components of queen substance and royal jelly of honeybees, respectively, were proposed starting with allyl bromide and 1,7-octadiene and using chemo-and regioselective transformations of the common intermediate building block 7-octen-1-ylacetate. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 58–60, January–February, 2008.     

Steroidal glycosides from Digitalis ciliata leaves

Two new steroidal glycosides of the spirostane and furostane classes, derivatives of gitogenin, were found in wastes from producing acetyldigitoxin preparation from Digitalis ciliata Trautv. (Scrophulariaceae). The structures of the glucosides were established using physical constants, chemical transformations, and IR, mass, and NMR spectra. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 452–455, September–October, 2006.     

Alkaloids from plants of the genus Nitraria

The new alkaloid schobericine was isolated from the aerial part of N. schoberi. The two new alkaloids komaroidine and acetylkomaroidine were isolated from the two Nitraria species N. komarovii and N. schoberi. Their structures were established using spectral data and chemical transformations. Their syntheses were carried out. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 164–166, March–April, 2006.     

Temperature changes of sorption parameters of di-n-alkylketones and methylcyclohexanones in capillary gas chromatography

The gas chromatographic behavior of di-n-alkylketones and isomeric methylcyclohexanones at variable temperatures in the isothermal runs has been studied using three capillary columns coated with SE-30, OV-225, and PEG-40M/KF stationary phases. The retention indices and their temperature increments were determined, and the partial molar free energies of the compounds under study were calculated. A linear dependence of the values of the partial molar free energy of sorption on the homologue number in di-n-alkylketones is not observed for the first member on the nonpolar SE-30 phase and for the third member on the polar OV-225 and PEG-40M/KF phases. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 328–332, February, 1997.     

Peculiar features of sorption of positional isomers of formyl-, acetyl-, and aminopyridines in capillary gas-liquid chromatography

The GLC retention parameters of α-, β-, and γ-isomers of formyl-, acetyl-, and aminopyridines were determined on two columns with stationary phases of different polarities. The contributions of formyl, acetyl, methyl, and amino groups located in the α-, β-, and γ-positions of the ring to the retention indices were calculated. The contributions of these groups to the retention were found to depend on their positions with respect to the N atom of the ring and are the smallest for α-substituents. The difference between pyridines containing electron-withdrawing substituents and those containing electron-donating substituents is manifested as different orders of elution of α-, β-, and γ-derivatives. The distinctions between the GLC behaviors of pyridines, benzenes, and furans with the same substituents were identified. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 91–94, January, 1997.     

Synthesis and high-resolution NMR spectra of A-nor-derivatives of 11-deoxyglycyrrhetic acid

Several skeletal and oxidative transformations of 11-deoxyglycyrrhetic acid were carried out to produce A-nor-derivatives. Signals for protons and C atoms in the PMR and ¹³C NMR spectra of the A-nor-derivatives were assigned using high-resolution ¹H (400 MHz) and ¹³C (125 MHz) NMR spectroscopy. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 445–448, September–October, 2006.