Relativistic molecular wavefunctions: XeF2

A new method is presented to calculate binding energies and eigenfunctions for molecules, using the relativistic Dirac hamiltonian. A numerical basis set of four component wavefunctions is obtained from atom-like Dirac-Slater wavefunctions. A discrete variational method has been developed and applied to the linear XeF₂ molecule.     

Molecular orbital study of molecular nitrogen fixation

The model systems of molecular nitrogen fixation [N₂ + H]?, [N₂ + H]⁺, [N₂ + H]^?, [N₂ + H₂], [N₂ + H₂]⁺, and [N₂ + H₂]^? were studied by the semiempirical INDO method. The study was based on the formal analogy between the catalytic reactions and the photochemical, radical, and ionic reactions on the other side. Symmetrical and donor-acceptor properties of necessary catalytic systems were proposed using the dependence of energy characteristics and electron structure on reaction coordinate. On the basis of this MO study we have proposed the appropriate symmetry types of catalysts for each of acceptable models of nitrogen fixation. For one of the proposed systems there was realised a model MO computation with explicit inclusion of atoms of transition metals (Fe, V).     

Thermochemical properties of benzoic acid derivatives VIII. Enthalpies of combustion and formation of o-, m-, and p- t-butylbenzoic acids

The enthalpies of formation in the crystalline state at 298.15 K of o-, m-, and p-t-butyl-benzoic acids have been determined by static-bomb calorimetry. Vapour-pressure determinations were made by the Knudsen-effusion technique and the sublimation enthalpies at the mean temperatures of the measurement ranges have been derived for the three acids. The values obtained are:

     

74.

Massenspektren neuer Phloroglucide,insbesondere solcher mit Valerylseitenketten     

M. Lounasmaa  C.-J. Widn  T. Reichstein 《Helvetica chimica acta》1973,56(3):1133-1144

Mass spectra of phloroglucinol derivatives recently isolated from African Dryopteris species are presented. Phloroglucides with n-valeryl side chain were found in these ferns for the first time. In the mass spectra they show strong peaks corresponding to loss of propene (C₃H₆) produced by McLafferty rearrangement, as shown in model compounds. Aside of the rottleron change (discussed formerly) this must be considered in order to avoid wrong interpretation, particularly when mass spectra are used to analyse mixtures of homologues, as usually present in the plants. If valeryl side chains are present other methods must be used therefore to measure the amount or show the absence of lower homologues with acetyl side chains.     

75.

Aktivierungsanalytische Untersuchungen an hochreinem Silicium     

W. Gebauhr  J. Martín und E Haas 《Fresenius' Journal of Analytical Chemistry》1964,200(4):266-278

Zusammenfassung Zur Aktivierungsanalyse von hochreinem Silicium wurden die vermuteten Verunreinigungen in 3 Gruppen entsprechend der Halbwertszeit ihrer zur Bestimmung herangezogenen Radionuklide zusammengefaßt und für diese Gruppen chemisch-analytische Trennungsgänge ausgearbeitet. Damit war es möglich, in relativ geringen Probemengen etwa 30 Elemente zu bestimmen. Die dargelegten Ergebnisse liegen durchweg im oder unter dem ppb-Bereich (=10^–7 %).Zur Lokalisierung einiger Verunreinigungen wird die Autoradiographie herangezogen. Einige Aufnahmen zeigen, daß dieses Verfahren auch bei Vorhegen äußerst geringer Aktivitäten noch wertvolle Aussagen zu liefern vermag.

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Summary For the activation analysis of high-purity silicon the supposed impurities are divided into 3 groups corresponding to the half-lives of the radionuclides belonging to the impurities. For these groups chemoanalytical separation schemes are developed. With this technique it was possible to determine about 30 elements in small samples. The results given are in or below the ppb-level.For localisation of the impurities autoradiography is used. Some of the pictures taken show, that also with very low activities valuable results can be obtained.

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Zum Schluntent/nm25j9047g653w5p/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> muntent/nm25j9047g653w5p/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> die freundliche Hilfe erwähnt werden, die wir an den deutschen Reaktorstationen bei der Durchuürung der Bestrahlung rehalten haben. So sind wir der Reaktorstation Garching, insbesondere den Harren Dr. Köhler und Rau zu auntent/nm25j9047g653w5p/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">erordentlichem Dank für die stats gewährte Unterstüzung bei der Bestrahlung der großen Zahl der Proben verpflichtet. — Die Analyse der kurzlebigen Radionuklide verlangte das Arbeiten direkt am Reaktor. Dank dem freundlichen Entgegenkommen der Herren Prof. Dr. E. Fischer und Dr. Röbert konnten wir dieses in einem Laboratorium der Reaktorstation Geesthacht durchführen, wobei wir auch den Herren Braun und Hauser für ihre bereitwillige Unterstützung zu danken haben.Schließlich sei Herrn Dr. Brandt für die Entwicklung der erwähnten Formel auch an dieser Stelle nochmals gedankt.

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In gekürzter Form anläßlich der Tagung der Fachgruppe: Kern-, Radio- und Strahlenchemie der Gesellschaft Deutscher Chemiker in Heidelberg am 10. 9. 1963 vorgetragen.     

76.

An nmr study of conformational exchange in some ketone-BF₃ and ether-BF₃ adducts     

J.S. Hartman  P. Stilbs  S. Forsén 《Tetrahedron letters》1975,16(40):3497-3500

     

77.

Synthesis and spectral properties of 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodi-azepine-2-thiones     

Eduardo CortS Corts  Carlos M. Alcocer Castrejn 《Journal of heterocyclic chemistry》1997,34(6):1809-1812

A series of twelve new 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodiazepine-2-thiones, which have potentially useful pharmacological properties, has been synthesized by condensing the 3,3-dimercapto-1-(para-substituted phenyl)-2-propen-1-one with 3,4-diaminophenyl-R-phenyl ethers. The structure of all products was corroborated by ir, ¹H-nmr, ¹³C-nmr and ms.     

78.

Microwave-assisted, solvent-free synthesis of 1-(α- or β-hydroxynaphthyl)-1,2,3,4-tetrahydroisoquinolines by the Mannich reaction     

István Szatmári 《Tetrahedron letters》2006,47(23):3881-3883

As a new extension of the Mannich reaction of naphthols, 1-(hydroxynaphthyl)-substituted 1,2,3,4-tetrahydroisoquinolines were synthesized by the nucleophilic addition of 1- or 2-naphthol to 3,4-dihydroisoquinolines under solvent-free conditions, using microwave irradiation. The additions to 3-methyl-6,7-dimethoxy-3,4-dihydroisoquinoline proved to be a highly diastereoselective processes, resulting in the cis isomers as the main or the only products.     

79.

On the accuracy of acid-base determinations from potentiometric titrations using only a few points from the titration curve     

Olin A  Wallén B 《Talanta》1977,24(5):303-308

There are several procedures which use only a few points on the titration curve for the calculation of equivalence volumes in acid-base titrations. The accuracy of such determinations will depend on the positions of the points on the titration curve. The effects of errors in the stability constants and in the pH measurements on the accuracy of the analysis have been considered, and the results are used to establish the conditions under which these errors are minimized.     

80.

Isotope dilution analysis in the micro and submicro range by double-labelling and precipitation on paper     

Weisz H  Kriván V 《Talanta》1969,16(7):823-826

A new variation of isotope dilution analysis based on double labelling and carried out on filter paper is described. The determination of microgram and submicrogram amounts of silver (labelled with (110m)Ag) by precipitation with iodide (labelled with (131)I) and of calcium (labelled with (45)Ca) by precipitation with phosphate (labelled with (32)P) are given as examples. In the first example the two radio-elements ((110m)Ag and (131)I) are measured by gamma-spectrometry, in the second one ((45)Ca and(32)P) by a beta-absorption method. A number of results show the usefulness of the method.     

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o-t-butylbenzoic acid	476.2 ± 1.9	99.8 ± 0.4	(at 314.6 K)
m-t-butylbenzoic acid	504.3 ± 1.6	103.0 ± 0.5	(at 326.5 K)
p-t-butylbenzoic acid	502.9 ± 1.7	103.8 ± 0.4	(at 334.1 K)

Massenspektren neuer Phloroglucide,insbesondere solcher mit Valerylseitenketten

Mass spectra of phloroglucinol derivatives recently isolated from African Dryopteris species are presented. Phloroglucides with n-valeryl side chain were found in these ferns for the first time. In the mass spectra they show strong peaks corresponding to loss of propene (C₃H₆) produced by McLafferty rearrangement, as shown in model compounds. Aside of the rottleron change (discussed formerly) this must be considered in order to avoid wrong interpretation, particularly when mass spectra are used to analyse mixtures of homologues, as usually present in the plants. If valeryl side chains are present other methods must be used therefore to measure the amount or show the absence of lower homologues with acetyl side chains.     

Aktivierungsanalytische Untersuchungen an hochreinem Silicium

Zusammenfassung Zur Aktivierungsanalyse von hochreinem Silicium wurden die vermuteten Verunreinigungen in 3 Gruppen entsprechend der Halbwertszeit ihrer zur Bestimmung herangezogenen Radionuklide zusammengefaßt und für diese Gruppen chemisch-analytische Trennungsgänge ausgearbeitet. Damit war es möglich, in relativ geringen Probemengen etwa 30 Elemente zu bestimmen. Die dargelegten Ergebnisse liegen durchweg im oder unter dem ppb-Bereich (=10^–7 %).Zur Lokalisierung einiger Verunreinigungen wird die Autoradiographie herangezogen. Einige Aufnahmen zeigen, daß dieses Verfahren auch bei Vorhegen äußerst geringer Aktivitäten noch wertvolle Aussagen zu liefern vermag.

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Summary For the activation analysis of high-purity silicon the supposed impurities are divided into 3 groups corresponding to the half-lives of the radionuclides belonging to the impurities. For these groups chemoanalytical separation schemes are developed. With this technique it was possible to determine about 30 elements in small samples. The results given are in or below the ppb-level.For localisation of the impurities autoradiography is used. Some of the pictures taken show, that also with very low activities valuable results can be obtained.

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Zum Schluntent/nm25j9047g653w5p/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> muntent/nm25j9047g653w5p/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> die freundliche Hilfe erwähnt werden, die wir an den deutschen Reaktorstationen bei der Durchuürung der Bestrahlung rehalten haben. So sind wir der Reaktorstation Garching, insbesondere den Harren Dr. Köhler und Rau zu auntent/nm25j9047g653w5p/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">erordentlichem Dank für die stats gewährte Unterstüzung bei der Bestrahlung der großen Zahl der Proben verpflichtet. — Die Analyse der kurzlebigen Radionuklide verlangte das Arbeiten direkt am Reaktor. Dank dem freundlichen Entgegenkommen der Herren Prof. Dr. E. Fischer und Dr. Röbert konnten wir dieses in einem Laboratorium der Reaktorstation Geesthacht durchführen, wobei wir auch den Herren Braun und Hauser für ihre bereitwillige Unterstützung zu danken haben.Schließlich sei Herrn Dr. Brandt für die Entwicklung der erwähnten Formel auch an dieser Stelle nochmals gedankt.

---

In gekürzter Form anläßlich der Tagung der Fachgruppe: Kern-, Radio- und Strahlenchemie der Gesellschaft Deutscher Chemiker in Heidelberg am 10. 9. 1963 vorgetragen.     

Synthesis and spectral properties of 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodi-azepine-2-thiones

A series of twelve new 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodiazepine-2-thiones, which have potentially useful pharmacological properties, has been synthesized by condensing the 3,3-dimercapto-1-(para-substituted phenyl)-2-propen-1-one with 3,4-diaminophenyl-R-phenyl ethers. The structure of all products was corroborated by ir, ¹H-nmr, ¹³C-nmr and ms.     

Microwave-assisted, solvent-free synthesis of 1-(α- or β-hydroxynaphthyl)-1,2,3,4-tetrahydroisoquinolines by the Mannich reaction

As a new extension of the Mannich reaction of naphthols, 1-(hydroxynaphthyl)-substituted 1,2,3,4-tetrahydroisoquinolines were synthesized by the nucleophilic addition of 1- or 2-naphthol to 3,4-dihydroisoquinolines under solvent-free conditions, using microwave irradiation. The additions to 3-methyl-6,7-dimethoxy-3,4-dihydroisoquinoline proved to be a highly diastereoselective processes, resulting in the cis isomers as the main or the only products.     

On the accuracy of acid-base determinations from potentiometric titrations using only a few points from the titration curve

There are several procedures which use only a few points on the titration curve for the calculation of equivalence volumes in acid-base titrations. The accuracy of such determinations will depend on the positions of the points on the titration curve. The effects of errors in the stability constants and in the pH measurements on the accuracy of the analysis have been considered, and the results are used to establish the conditions under which these errors are minimized.     

Isotope dilution analysis in the micro and submicro range by double-labelling and precipitation on paper

A new variation of isotope dilution analysis based on double labelling and carried out on filter paper is described. The determination of microgram and submicrogram amounts of silver (labelled with (110m)Ag) by precipitation with iodide (labelled with (131)I) and of calcium (labelled with (45)Ca) by precipitation with phosphate (labelled with (32)P) are given as examples. In the first example the two radio-elements ((110m)Ag and (131)I) are measured by gamma-spectrometry, in the second one ((45)Ca and(32)P) by a beta-absorption method. A number of results show the usefulness of the method.