Rolf Borsdorf

Quantenchemische berechnungen zur struktur des 1,2-dithiins

Zusammenfassung Quantenchemische Berechnungen bestatigen fur 1,2-Dithiin die vorgeschlagene Heterocyclenstruktur. Mit dem PPP-Verfahren lasst sich die Farbigkeit dieser Verbindung interpretieren. EHT-Rechnungen zeigen die positive Gesamtuberlappungspopulation der SS-Bindung an.

NMR-SPEKTROSKOPISCHE UNTERSUCHUNGEN AN DERIVATEN DES 2,4-DICHLORPHENOXYESSIGSAUREHYDRAZIDS

SummaryDerivatives of 2,4-dichlorphenoxyacetyl-hydrazides were prepared by reaction of the hydrazides with different aldehydes. NMR-spectroscopic investigations of these compounds show the existence of rotamers resulting from a nitrogen-carbonyl bond rotation. Contrary to substituted dithiocarbacinic acid derivatives noE/Z-isomerism relative to the C=N double bond could be demonstrated. In order to prove the structures we utilized chemical shift differences in the1H-,13C- and15N-NMR-spectra, NH and CH coupling constants and NOE-difference measurements. The barriers of rotation were determined by NMR-measurements at various temperatures and line shape analysis using the computer program D-NMR 3.

Kombinierte d-NMR- und LIS-Untersuchungen zum konformativen Verhalten von Formylmethylenthiopyranen

The rotational barriers ΔG≠ toE,Z- ands-cis, s-trans-isomerisation in formylmethylenthiopyranes are determined and discussed with regard to their dependence on substituent effects. Preferential conformers are distinguished by lanthanide induced shifts. Best fits between calculated and experimental shifts are obtained forE,s-trans andZ,s-cis isomers. The results indicate a nonbonding interaction between aldehyde oxygen and ring sulphur, favourings-cis conformation in case ofZ configuration.

119Sn-NMR-spektroskopische Untersuchungen an Tri-n-butylzinnderivaten von N-Acetylaminosäuren

SummaryEleven compounds have been prepared by azeotropic destillation of water from toluene solutions of bis(tri-n-butyltin)oxide and N-acetyl amino acids. All derivatives are white solids.119Sn-NMR-spectra of the tri-n-butyltin compounds have been studied in coordinating and non coordinating solvents. The chemical shifts and the coupling constants1J(119Sn,13C) depend significantly on the coordination number of the tin atom and on the properties of the substituents. The data for the compounds are discussed in comparison with those for other tri-n-butyltin compounds.

NMR spectroscopic determination of enantiomers via their triphenyltin derivatives: A new application of chiral solvating agents

A method is described for the NMR determination of the enantiomeric composition of chiral carboxylic acids and alcohols using their triphenyltin derivatives together with the chiral solvating agents quinine hydrochloride and phenylethylamine.

Cyclische sulfone. I: Polarographischer nachweis von transanularen carbonyl-sulfon-wechselwirkungen in thiacycloalkanon-1,1-dioxiden

Zusammenfassung Die polarographische Reduktion der Carbonylgruppe in Thiacycloalkanon-1,1-dioxiden ist gegenuber den Thiacycloalkanonen auf Grund einer verstarkten transanularen Wechselwirkung wesentlich erleichtert. Die vermessenen Halbstufenpotentiale hangen von der gegenseitigen Stellung der Carbonyl- und Sulfongruppierung ab. Thiacycloalkanon-(3)-1,1-dioxide werden leichter als Thiacycloalkanon-(4)-1,1-dioxide reduziert. Die Lage, der Halbstufenpotentiale ist weiter von der Ringgrosse abhangig.

NMR-spektroskopische Untersuchungen zurE/Z-Isomerie von substituierten Dithiocarbazinsäurederivaten

SummaryNMR-spectroscopic investigations of substituted dithiocarbacinic acid derivatives show the existence of configurational isomers relative to the C=N double bond, but no tautomerism. We applied chemical shift differences in the1H-,13C- and15N-NMR-spectra, N - H and C - H coupling constants and NOE difference measurements in the solvents CDCl3,DMSO-d6 and partly CD3OD in order to discriminate between the isomers and to determine the configurational composition. Compounds4 and5 exist asE-isomers in all solvents, compounds1, 2 and3 as a mixture ofE/Z-isomers. InDMSO-d6 theE-form is the preferred isomer.

Polarographischer Nachweis der Carbonyl-Schwefel-Wechselwirkung in Thiacyclanonen

Zusammenfassung Die polarographische Reduktion der Carbonylgruppe in Thiacyclanonen ist auf Grund einer Carbonyl-Schwefel-Wechselwirkung gegenuber Cyclanonen betrachtlicht erleichtert. Es kann eine deutliche Abhangigkeit der Halbstufenpotentiale von der gegenseitigen Stellung der Carbonyl-und Thioathergruppierung festgestellt werden. Thiacyclanone-3 werden leichter als Thiacyclanone-4 und diese leichter als Thiacyclanone-5 reduziert. Die Lage der Halbstufenpotentiale wird weiter durch die Ringgrosse beeinflusst.

Characterization of alcohols, thiols and carboxylic acids in mixtures using the 119Sn-chemical shift of their tri-n-butyltin derivatives

SummaryMixtures of tri-n-butyltin thiolates, -alcoholates and -carboxylates were investigated. A characterization of diastereomeric compounds using their 119Sn-NMR-spectra was of special interest. It is shown that 119Sn-NMR spectroscopy is a useful method for the analysis of these mixtures.

Bestimmung der integralen molaren Extinktionskoeffizienten im IR für äquatoriale und axiale C—Halogen-Valenzschwingungen

Using the population ratios of the different conformations measured by NMR peak area method at low temperatures we determined the integrated molar extinction coefficients of the C-X stretching vibrations in the IR spectra of cyclohexyl-chloride, -bromide and -iodide under the same conditions. The obtained values are compared with the integrated molar extinction coefficients of the conformationally homogeneouscis- andtrans-4-tert-butylcyclohexyl derivatives, which are assumed to reflect the spectroscopic properties of the axial and equatorial conformations of the monosubstituted cyclohexanes.