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  • 1
    Electronic Resource
    Electronic Resource
    13C-NMR-chemische Verschiebungen von Polymethinen. Elektronenstruktur und Lösungsmitteleinfluss6. Mitteilung über Solvatochromieprobleme. 7. Mitt. vergl.1 (1972)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 4 (1972), S. 571-576 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The 13chemical shifts of simple polymethines (cyanines and merocyanines) show the very pronounced charge alternation in these compounds. The 13C shifts of polar merocyanines are also susceptible to solvent polarity, which in this case has a strong influence upon the electron structure.
    Notes: Die 13C-NMR-chemischen Verschiebungen von einfachsten Polymethinen bestätigen die alternierende Elektronendichteverteilung bei diesen Verbindungen. Die Verschiebungen polarer Merocyanine sind von der Polarität des Lösungsmittels abhängig und beweisen damit eine lösungsmittelinduzierte Veränderung der Elektronenstruktur.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270040418
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  • 2
    Electronic Resource
    Electronic Resource
    Struktur-Reaktivitätsuntersuchungen mit heterosubstituierten Nitrilen - VII:VI Mitteilung, siehe Lit. 1. 13C-, 14N- und 19F-NMR-Spektroskopische Untersuchungen an Verbindungen vom Typ Ar—X—C≡N (1973)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 5 (1973), S. 419-422 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The chemical shifts of aromatic nitriles of the general structure para-Y—C6H4—X—CN with X = O, S, Se and N(CH3) have been investigated by the 13C NMR technique. For cyanates (X = O) the 14N shifts and for Y = F the 19F shifts were likewise measured. The chemical shifts and the corresponding 13C shift increments Δn have been found to correlate with the appropriate substituent constants σR0, σp0 and σI, as well as with the π-electron densities calculated in the PPP approximation.
    Notes: An aromatischen Nitrilverbindungen der allgemeinen Struktur para-Y—C6H4—X—CN mit X = O, S, Se und N(CH3) wurden die 13C-NMR- sowie für X = O die 14N-NMR-und für Y = F die 19F-NMR-chemischen Verschiebungen bestimmt. Die Meßergebnisse wurden in Zusammenhang mit der elektronischen Struktur der Moleküle (Substituentenkonstanten, π-Elektronendichten in PPP-Näherung) diskutiert.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270050906
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  • 3
    Electronic Resource
    Electronic Resource
    Zur Interpretation 29Si-NMR-chemischer Verschiebungen (1973)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 5 (1973), S. 561-566 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The 29Si-NMR chemical shifts δ(29Si) of (CH3)4-nSiXn compounds and some 13C-NMR chemical shifts δ(13C) of analogous carbon compounds are discussed by means of relative paramagnetic screening constants σ*, calculated by a simplified model. In this model only the Si(3P)- and C(2P)-orbitals are considered; for the calculations, the electronegativities of Si, C and the X-substituents and a single empirical parameter are necessary. The calculated values of σ* are in good agreement with the change of the chemical shifts which are observed for the (CH3)4-nMXn compounds with different X and n. These results clearly show that δ(29Si) and δ(13C) depend primarily on the σ-charge of the Si- and C-atom, and that (P—d)π-interactions on the Si-atom are of minor importance.
    Notes: Zusammenfassung-die 29Si-NMR-chemischen Verschiebungen δ(29Si) einer größeren Zahl von Verbindungen des Typs (CH3)4-nSiXn sowie δ(13C) einiger analoger Kohlenstoffverbindungen werden mit Hilfe von relativen paramagnetischen Abschirmungskonstanten σ* diskutiert, die nach einem vereinfachten Berechnungsverfahren bestimmt werden. Für die Berechnung von σ* werden nur p-Orbitale berücksichtigt, als Ausgangsgrößen sind lediglilch die Elektronegativitäten von Si, C und X sowie ein einziger empirischer Korrekturfaktor erforderlich. Die berechneten Änderungen von σ* befinden sich in guter Übereinstimmung mit dem Gang der experimentellen Verschiebungen, die in den (CH3)4-nMXn-Verbindungen in Abhängigkeit von Zahl und Art der Substituenten X beobachtet werden. Die erhaltenen Ergebnisse zeigen, daß δ(29Si) und δ(13C) im wesentlichen durch die σ-Ladung am Si-bzw. C-Atom bestimmt werden und daß (p - d)π Wechselwirkungen am Si-Atom nur eine untergeordnete Bedeutung besitzen.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270051203
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  • 4
    Electronic Resource
    Electronic Resource
    A comment on the interpretation of 13C n.m.r. δ-syn-axial substituent effects in cyclic moleculesPart IV in the series ‘Stereochemical investigations by 13C-NMR’; for part III, see Ref. 1. (1976)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 8 (1976), S. 655-657 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An alternative explanation for δ-syn-axial substituent effects of 13C chemical shifts is given using the concept that the δ-syn-axial interaction in the substituted compound replaces the γ-gauche interaction in the parent molecule. The application of this principle to substituted norbornanes and steroids leads to the conclusion that the ‘net steric’ δ-syn-axial shift is upfield rather than downfield.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270081213
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  • 5
    Electronic Resource
    Electronic Resource
    Steric gamma effect on 29Si shielding in (CH3)3Si—O—C—R groups (1977)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 9 (1977), S. 239-240 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that a γ-methyl group causes approximately a 3 ppm upfield shift of the silicon resonance in (CH3)3Si—O—C—CH3 fragments. It is estimated that polar effects contribute about 0.8 ppm to this shift leaving a net steric γ upfield shift of 2 ppm. Variations around these average values are interpreted by different conformer populations, the importance of which are illustrated by the shifts in trimethylsiloxy derivatives of adamantane.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270090414
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  • 6
    Electronic Resource
    Electronic Resource
    29Si NMR spectra of methylphenylcyclotri-and -tetrasilazanes (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 18 (1982), S. 71-73 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 29Si NMR spectra of various methylphenyl-substituted cyclotri- and -tetrasilazanes, composed of different combinations of the units d = Me2SiNH, dph = MePhSiNH and dph2 = Ph2SiNH, have been investigated. For most of the compounds having more than one asymmetric centre, the spectra of both the individual isomers and their mixtures have been studied, and the signals of the individual isomers have been assigned. The effect of a different arrangement of phenyl groups in the rings, and the influence of the stereochemistry of the isomers on the 29Si chemical shifts in cyclotri- and -tetrasilazanes have been studied. The 29Si chemical shifts in cyclotrisilazanes are additive and can be represented as the sum of increments corresponding to the number and positions of the phenyl groups in the rings. In these compounds, the spatial structure of the isomers does not exert any noticeable effect on the spectra. On the contrary, chemical shifts are not simply additive in cyclotetrasilazanes: a pronounced stereochemical dependence is apparent.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270180204
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  • 7
    Electronic Resource
    Electronic Resource
    Gaschromatographische und 29Si-NMR-spektroskopische Untersuchungen an Kieselsäuretrimethylsilylestern (1976)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 424 (1976), S. 115-127 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Gaschromatographic and 29Si-NMR Spectroscopic Investigations on Silicic Acid TrimethylsilylestersSilicic acid trimethylsilylesters of different constitutions are characterized by gaschromatographic retention index and retention temperatures. It is shown that the retention indices of the esters depend mainly on the number of trimethylsilylgroups in the molecule and exhibit only small effects of the constitution of the silicic acid framework. The 29Si-n.m.r. spectra of 9 silicic acid TMS-esters of different constitutions are recorded and the assignment of the signals to the individual building units of the esters are discussed. On the basis of these results the constitutions of hexamer silicic acid-TMS-esters is investigated. Two isomers of the bicyclo-hexasilicic acid ester [(CH3)3Si]10 [Si6O17] could be identified.
    Notes: Kieselsäuretrimethylsilylester unterschiedlicher Konstitution werden mit Hilfe der Gaschromatographie hinsichtlich ihres Retentionsindex und der Retentionstemperatur charakterisiert. Es wird gezeigt, daß die Retentionsdaten der Ester im wesentlichen von der Anzahl der Trimethylsilylgruppen im Molekül abhängen und nur wenig von der Konstitution des Kieselsäuregerüstes beeinflußt werden. Die 29Si-NMR-Spektren von neun Kieselsäure-TMS-Estern unterschiedlicher Konstitution wurden aufgenommen und die Zuordnung der Signale zu den einzelnen Baugruppen der Ester diskutiert. Auf der Grundlage dieser Ergebnisse wurden Konstitutionsuntersuchungen an hexameren Kieselsäure-TMS-Estern durchgeführt, die zur Identifizierung von zwei Isomeren des Bicyclohexakieselsäureesters [(CH3)3Si]10[Si6O17] führten.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19764240205
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  • 8
    Electronic Resource
    Electronic Resource
    29Si-NMR-Spektroskopie an Silicatlösungen. V. über die 29Si-NMR-Spektren niedermolekularer Kieselsäuren (1977)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 437 (1977), S. 249-252 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 29Si-N.M.R. Spectroscopy of Silicate Solutions. V. On the 29Si-N.M.R. Spectra of Low-molecular Silicic AcidsThe 29Si-n.m.r. signals of the end groups of di- and trisilicic acid (each in 0,5 M aqueous solution) are lying in a very close neighbourhood (Δδ = 0,03 ppm). In more concentrated solutions (1.5M) the end group signals approach to oneanother and overlap respectively in such a strong manner, that their unambiguous assignment and, hence, the identification of the low-molecular condensation products of monosilicic acid are up to now not possible.
    Notes: 29Si-NMR-Untersuchungen an 0,5 m Di- und Trikieselsäurelösungen zeigen, daß die Resonanzsignale für die Endgruppen-Si-Atome der beiden Kieselsäuren sehr eng benachbart sind (Δδ = 0,03 ppm). In konzentrierten 1,5 m Lösungen nähern bzw. überlagern sich die Endgruppensignale derart, daß eine eindeutige Zuordnung der Resonanzsignale und die Identifizierung nieder-molekularer Kondensationsprodukte der Monokieselsäure bisher nicht möglich ist.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19774370136
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  • 9
    Electronic Resource
    Electronic Resource
    Über die Silicatanionenkonstitution in Tetraethylammoniumsilicaten und ihren wäßrigen Lösungen (1980)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 465 (1980), S. 15-33 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Constitution of Silicate Anions in Tetraethylammonium Silicates and their Aqueous SolutionsInvestigations by paperchromatography, 29Si-NMR spectroscopy and trimethylsilylation method show that concentrated solutions of tetraethylammonium (TEA) silicates with molar TEA:Si ratios from 2.8 to 1 contain mainly double three-ring silicate anions. Besides of these small amount of mono-, di-, tri-, tetra-, cyclotri-, cyclotetra-, double four-ring- and other polycyclic silicate anions are present. From these solutions a crystalline double three-ring silicate of the formula [N(C2H5)4]6[Si6O15] · 57 H2O could be obtained by crystallization at low temperature. Concentrated solutions with TEA:Si ratios of 0.8 to 0.6 contain mainly double three-, double four-, double five- an probably double six-ring silicate anions. From such solutions always the solid TEA-double four-ring silicate is obtained by crystallization. The reasons for the prefered formation of double ring silicate anions in TEA-silicate solutions and their crystallization are discussed.
    Notes: Untersuchungen mit Hilfe der Papierchromatographie, 29Si-NMR und Trimethylsilylierungsmethode ergaben, daß in konzentrierten Tetraethylammoniumsilicatlösungen mit molaren TEA:Si-Verhältnissen von 2,8 bis 1 neben geringen Konzentrationen an Mono-, Di-, Tri-, Tetra-, Cyclotri-, Cyclotetra-, Doppelvierring- und weiteren polycyclischen Silicatanionen, vorwiegend Doppeldreiringsilicatanionen vorliegen. Bei tieferen Temperaturen kristallisiert aus diesen Lösungen ein Doppeldreiringsilicat der Formel [N(C2H5)4]6[Si6O15] · 57 H2O aus. Konzentrierte Lösungen mit TEA:Si = 0,8 bis 0,6 enthalten hauptsächlich Doppeldrei-, Doppelvier-, Doppelfünf und wahrscheinlich auch Doppelsechsringsilicatanionen. Aus diesen Lösungen kristallisiert stets das TEA-Doppelvierringsilicat aus. Die möglichen Ursachen für die bevorzugte Bildung von Doppelringsilicatanionen in TEA-Silicatlösungen und deren Kristallisation werden diskutiert.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19804650103
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  • 10
    Electronic Resource
    Electronic Resource
    Zur Frage der Verteilung der Silicium- und Aluminiumatome im Kristallgitter von Zeolithen. Ein alternativer Strukturvorschlag für Zeolithe vom Typ NaA (1980)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 468 (1980), S. 35-38 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Distribution of Silicon and Aluminium Atoms in the Crystal Lattice of Zeolites. An Alternative Structure of NaA-Type ZeolitesInvestigations by high resolution solid state 29Si NMR of zeolites have shown that the crystal lattice of NaA-type zeolites (Si/Al = 1) consists of SiO4 tetrahedra which are connected with three Al and one Si atom. This leads to a structure of the Zeolite lattice in which in contradiction to LOEWENSTEIN'S rule AlOAl connections are present. The space group of this type of lattice should be not Fm3c.
    Notes: Untersuchungen mit Hilfe der hochauflösenden 29Si-NMR-Spektroskopie an pulverförmigen Zeolithen ergaben, daß das Kristallgitter des NaA-Zeoliths (Si/Al = 1) einheitlich aus Sio4-Tetraedern aufgebaut ist, an die drei Al-und ein Si-Atom gebunden sind. Daraus folgt eine Gitterstruktur, die unter Verletzung der LOEWENSTEINSCHEN Regel AlOAl-Verknüpfungen aufweist und der im Gegensatz zu bisherigen Annahmen die Raumgruppe Fm3c nicht zugeordnet werden kann.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19804680105
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