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  • 1
    Electronic Resource
    Electronic Resource
    Thermodynamic characteristics of sorption of heterocyclic compounds m capillary gas chromatography (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 1928-1933 
    Details
    ISSN: 1573-9171
    Keywords: capillary gas chromatography ; thermodynamic characteristics of sorption ; heterocyclic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dependences of sorption energies of sulfur-, oxygen-, and nitrogen-containing heterocyclic compounds on the nature of heteroatoms, structure of substituents and their position in the ring were studied. The contributions of heteroatoms, functional and alkyl groups to the energy of dispersive interaction of position isomers with nonpolar stationary phases were determined for imidazoles, piperidines, morpholines, thiomorpholines, dioxalanes, oxathiolanes, dithiolanes, thiophenes, and furans. The nonequivalence of contributions of the same substituents to the sorption energy of each of the heterocyclic compounds, depending on the nature of the heteroatom and position of the substituent, was shown. The obtained values of contributions of heteroatoms and substituents can be used for apriori calculation of retention indices of position isomers of five- and six-membered heterocycles containing one or two heteroatoms in the ring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01457779
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  • 2
    Electronic Resource
    Electronic Resource
    Chromatographic and IR characteristics of methyl-, formyl-, and acetyl-substituted furans and thiophenes (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 64-69 
    Details
    ISSN: 1573-9171
    Keywords: capillary gas chromatography ; FTIR spectroscopy ; methyl-, formyl-, and acetyl-substituted furans and thiophenes ; scheme for prediction of retention indices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The GC and FTIR spectral characteristics of methyl-, formyl-, and acetyl-substituted furans and thiophenes were determined. The substituent contributions to the retention indices were calculated. It was found that contributions of identical substituents differ according to the nature of the heterocycle, their position relative to the heteroatom and other neighboring groups. The contributions of CH3-, CHO-, and COCH3-groups in the β-position of the cycle for monosubstituted substances were equal to the contributions of these groups in monosubstituted benzenes. The contributions of carbonyl groups in theα-position were greater than in the β-position for the same groups. The contributions were found to be nonadditive for disubstituted methyl and carbonyl-containing thiophenes and furans. The presence of two carbonyl groups as substituents in furans and thiophenes results in reduction of the sorption energy of the latter, which is known as «negative» α-effect. The scheme fora priori calculation of retention indices taking into account the non-uniformity of the contributions of methyl and carbonyl substituents in thiophenes and furans was suggested. The indices of 12 unknown substances of these classes were calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00699137
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  • 3
    Electronic Resource
    Electronic Resource
    Gas chromatographic determination of the free energy of sorption of methylene units ofN-alkylsubstituted six-membered cyclic amines (1994)
    Springer
    Russian chemical bulletin 43 (1994), S. 395-397 
    Details
    ISSN: 1573-9171
    Keywords: capillary gas chromatography ; N-alkylsubstituted piperidines ; morpholines ; thiomorpholines ; free energy of sorption of CH2 units
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The free energy of sorption of methylene units, ΔG(CH2), for the homologous series ofN-alkylsubstituted morpholines, thiomorpholines, piperidines and 2-methyl-, 3-methyl-, 4-methyl- and 2,6-dimethylpiperidines was determined. It was shown that the dependence of these values on the number of CH2 units in the carbon chain is not linear. Universal equations for calculating the values of the energy contribution depending on the number of CH2 units in the carbon chain were obtained. Abnormally high values of free energy of sorption of the first CH2 unit were found in all series studied and reasons for the anomaly are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01169713
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of time and temperature on the preparation of pyrazines in model reactions of the synthesis of aroma-forming substances (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 1258-1263 
    Details
    ISSN: 1573-9171
    Keywords: pyrazines ; Maillard reaction ; capillary gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The qualitative and quantitative compositions of pyrazines that form in model glucose—ammonia and glucose—ammonia—leucine reactions in a glycerol medium were studied. Reaction conditions were found that ensure the synthesis of 23 alkylpyrazines in total concentration ∼6 g/kg. The obtained mixture of pyrazines is promising for use in the development of food aroma-forming substances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00864192
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  • 5
    Electronic Resource
    Electronic Resource
    Sorption characteristics ofN-alkylimidazoles under conditions of capillary chromatography (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 300-304 
    Details
    ISSN: 1573-9171
    Keywords: capillary gas chromatography ; homologous series ; alkyl substitutedN-alkylimidazoles ; retention indices ; equations ; contributions of alkyl groups at the C and N atoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The retention indices forN-n-alkyl (C1-C5) substituted imidazoles with Me, Et, Pr, and Bu groups in different positions of the cycle were determined. Two capillary columns with OV-101/KF and PEG-40M/KF were used. The two nitrogen atoms of the imidazole molecule were shown to have different effects on the contributions of the alkyl groups to the retention indices. The maximum and minimum contributions are observed for the substituents at the 5 and 4 positions of the imidazole cycle, respectively. An increase in a size of the C m H2m+1 substituent attached to the N(1) atom has a notable effect only on the contributions of the alkyl groups at the 2 and 5 positions. The retention indices values for a homologous series with ann-alkyl group attached to the N or C(2) atom were described by a universal type equation. The obtained equations can be used for predicting the retention indices of new homologs and identification ofN-alkylimidazoles in complex mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702140
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  • 6
    Electronic Resource
    Electronic Resource
    Sorption properties of heterocyclic compounds differing by heteroatom in capillary gas chromatography (1993)
    Springer
    Russian chemical bulletin 42 (1993), S. 1167-1170 
    Details
    ISSN: 1573-9171
    Keywords: capillary gas chromatography ; retention indices ; substituted thiophenes ; furans ; oxathiolanes ; dithiolanes ; dioxolanes ; oxathianes ; dithianes ; dioxanes ; analogy of sorption properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dependence of sorption properties on the nature of heteroatoms in substituted five- and six-membered heterocyclic compounds with two heteroatoms (sulfur and oxygen), thiophenes and furans bearing alkyl, formyl, acetyl, and sulfide substituents have been investigated. Equations for calculating the retention indices of analogs have been proposed, and the indices of 35 previously non-investigated substances of these classes have been predicted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00701998
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