Showing papers by "University of Basel published in 1971"

A study of the molecular structure and of the barrier to methyl rotation in o-chlorotoluene partially oriented in the nematic phase

Abstract: The N.M.R. spectrum of o-chlorotoluene, dissolved in the nematic phase of 4-methoxybenzylidene-4-amino-α-methylcinnamic acid n-propylester is analysed and the shape of the proton skeleton determined. The position of lowest energy of the potential barrier to methyl rotation is found to be that in which the chlorine atom is staggered to the methyl group, and the height of the barrier is of the order of 5·0 kJ mol-1 (1200 cal/mole).

A spin label study of sarcoplasmic vesicles

Abstract: Spin labeled fatty acids have been incorporated as structural probes into sarcoplasmic vesicles isolated from rabbit skeletal muscle. The evaluation of the electron paramagnetic resonance spectra has yielded the following results: 1 The spin labels I (m,n) display a fast, anisotropic rotation in the sarcoplasmic membrane. The first 7 carbon-carbon bonds adjacent to the carboxyl group of the spin labeled fatty acid experience a highly ordered environment, whereas for n > 7 a pronounced increase in the flexibility of the hydrocarbon chain is observed although the system is still more ordered than pure lipid dispersions. The fluidity of the membrane is due to its lipid constituents, since a removal of the lipids leads to spectra characteristic for immobilized spin labels. 2 The comparison of several model systems leads to the assumption that a direct lipidprotein interaction must play an essential role in the organization of the membranous lipids. The effect of this interaction is to increase the stiffness of the hydrocarbon chains of the lipid moieties. 3 The activity of the calcium dependent ATPase is directly related to the fluidity of the membrane. If the enzymatic activity of a lipid deficient membrane is restored by the addition of oleic acid, the oleic acid assumes a physical state which is very similar to that of the natural membranous lipids.

The Structure of the Ferrocenyl‐Methyl Cation. Preliminary communication

Abstract: Using a modified Extended Huckel (S. C. C.) procedure the structure of the ferrocenyl-methyl cation has been calculated. The result is a structure (V) with about equal overlap population between all FeC bonds. The methylene group is bent towards the iron atom and both rings are tilted.

The Competition between Spin Orbit Coupling and Conjugation in Alkyl Halides and its Repercussion on their Photoelectron Spectra

Abstract: A crude molecular orbital model for alkyl halides is proposed, which provides a semi-quantitative rationalization for the following experimental observations: (a) In the photoelectron spectra of alkyl halides RX (symmetry C8) the lone pair band is split into two components, separated by a gap Δ. This gap is equal to the splitting associated with spin-orbit coupling in systems where X lies on a symmetry axis of order n ≥ 3. (b) The vibrational pattern of the two components indicates substantial conjugation between R and X. (c) Notwithstanding (b), the gap Δ is largely independent of the type of alkyl group R. (d) For strongly conjugating alkyl groups (e. g. R = cyclopropyl) the first component of the lone pair band (i. e. the one at lower ionization potential) broadens while the one at higher potential sharpens up.

Das Alpen-Dinariden-Problem und die Palinspastik der südlichen Tethys

Abstract: Tektonische Lage und Sedimentationsgeschichte fassen Sudalpin-Ostalpininterne (subtatrische und sudlichere) Karpaten und Dinariden zu einer Einheit zusammen, die einen Teil des sudlichen Kontinentalrandkomplexes der Tethys gebildet hatte. Zur Rekonstruktion dieses Kontinentalrandes ist eine palinspastische, die alpinen Deformationen entzerrende Rekonstruktion notig. Versuche in dieser Richtung zwingen zu einer neuen Analyse des Alpen-Dinariden-Problems. Ausgehend von den gro\en prAoligozAnen Schubweiten in den nordvergenten Alpen und Karpaten einerseits, den sudvergenten Helleniden und damit wahrscheinlich auch den Dinariden andererseits gelangt man zum Schlu\, da\ aus dem heutigen tektonischen ubereinander ein palAogeographisches Nebeneinander nur durch Annahme von mindestens zwei aufeinander folgenden Bewegungsphasen von ganz verschiedener Tendenz zu bewerkstelligen ist. Vor dem UnteroligozAn entstand der Hauptteil des nordvergenten alpinen sowie des sudvergenten dinarisch-hellenischen DeckengebAudes. Der Vergenzwechsel zwischen dem Ostende der slowakischen Karpaten bei Kosice und dem Westende der innerdinarischen Einheiten bei Zagreb verlangt eine dextrale Senke-Senke-Verschiebungszone, die heute zerrissen ist. Um den Zusammenhang wiederherzustellen und gleichzeitig palinspastischen Raum zu schaffen fur die Dinariden, wird eine jungtertiAre dextrale Verschiebung von im Osten 300 km lAngs der insubrischen Linie s. l. postuliert, deren Implikationen besonders auch in den Westalpen und an der Karpaten-Balkan-Grenze spurbar sein mussen.

Zur Cytologie der pränatalen Gonaden-Entwicklung beim Menschen

Abstract: Es wurden die Anlagen von 16 menschlichen, embryonalen und fetalen Hoden mit dem Elektronenmikroskop untersucht. Das Alter der Embryonen reichte von 40 Tagen bis zu 22 Wochen Ovulationsalter (OA). Untersucht wurden die cytologischen Veranderungen der mannlichen Keimzelle. Dabei gelang eine eindeutige Abgrenzung von zwei Geschlechtszelltypen durch cytomorphologische Kriterie: “Gonocyten” findet man vorwiegend bis zur 12. Woche. Sie sind in einer I. Phase uberwiegend frei von Glykogen und in einer 2. Phase etwa ab dem 45. Tag OA durch zunehmende Glykogeneinlagerung im Cytoplasma charakterisiert. In einer 3. Phase ab der 10.–12. Woche treten neben den Gonocyten “fetale Spermatogonien” auf, die ab der 18. Woche etwa ein Drittel der vorhandenen Geschlechtszellen ausmachen. Fetale Spermatogonien sind an einem lockeren Kern, an der veranderten Mitochondrienstruktur, dem Auftreten von intermitochondrialer Substanz und intercellularen Brucken sowie dem Fehlen von Glykogen zu erkennen. Ein Teil dieser fetalen Spermatogonien zeigt degenerative Zellveranderungen, die als Zeichen eines spateren Zelltodes gewertet werden. Die Frage, ob Gonocyten oder fetale Spermatogonien den Zellpool darstellen, aus dem sich die Spermatogonien des postnatalen und adulten Hodens entwickeln und ableiten, wird diskutiert, kann aber mit dem vorhandenen Material und den Ergebnissen nicht beantwortet werden.

Field ionization mass spectrometry—III: Cardenolides

Abstract: The electron impact (EI) and field ionization (FI) mass spectra of some representative underivatized cardenolides have been studied together for the first time, with the objective of assessing the structural and in particular the sequence information afforded by this promising analytical method. Two series of cardenolides have been examined, each consisting of a mono-, di- and trisaccharide glycoside. The first was based on the aglycone digitoxigenin and comprised neriifolin, thevebioside and cerberoside; the second was based on the genin strophantidin and included cymarin, K-strophantin-β and K-strophantoside. Other cardiac glycosides investigated and discussed include digitoxin and helveticoside. Important and structurally diagnostic fragmentations have been uncovered, especially in FI mode. In addition, the EI and FI spectra of individual components of the cardenolides have been recorded, e.g. the genins digitoxigenin and strophantidin, and the mono-saccharides L-thevetose, D-cymarose and D-glucose.

Photoelectron‐Spectroscopic Evidence for the Orbital Sequence in Fulvene and 3, 4‐Dimethylene‐cyclobutene

Abstract: The photoelectron spectra of fulvene (II) and of 3,4-dimethylene-cyclobutene (III) have been recorded. The PE. bands are correlated, in order of increasing ionisation potentials, with the following orbitals: II: 1a2(π), 2b1(π), 7b2(π), 1b1(π); III: 2b1(ω), 1a2(π), 10a1(ω), 8b2(ω), 1b1(π). This assignment is based on a semi-quantitative perturbation MO-model and on the SCF-LCAO-MO calculations reported by Praud, Millie & Berthier [5] for benzene, II and III.

Die konjugative Wechselwirkung zwischen π- und Walsh-Orbitalen: Das Photoelektron-Spektrum des Homofulvens.

Abstract: Analysis of the photoelectron spectrum of homofulvene (1) (spiro [2.4] hepta-4,6-diene) confirms the conclusions previously drawn concerning the direct conjugation between π-and Walsh-orbitals. It is shown that the resonance integral (4) appropriate for the semi-quantitative interaction of these orbitals amounts to −1.9 eV, i.e. nearly the value for conjugating π-orbitals (β = −2.4 to −2.5 eV). This explains the close analogy between the photoelectron spectrum of 1 and that of fulvene.

An Estimate of the Interatomic Distances in Monohaloacetylene Radical Cations from Photoelectron-spectroscopic Data†

Abstract: A convenient method is given for the semiquantitative determination of those changes ΔSi in internal coordinates, which describe the structure of the radical cation M+(Ψ) relative to the neutral molecule M in its electronic ground state. The changes ΔSi correspond to those associated with the relaxation process which follows the ionisation M + hv → M+(Ψ) + e, M+ being in the electronic state Ψ. The method, based on the procedure originally developped by Smith & Warsop [3], uses the spacing and relative intensity of the vibrational fine-structure components of the bands in the photoelectron spectrum of M. From these data are calculated the changes ΔQk in normal coordinates, which are then transformed into the ΔSi by applying the L-matrix. The changes ΔRCX, ΔRCC and ΔRCH which describe the structure of the radical cations of the four monohaloacetylenes I(X) (X = F, Cl, Br, I) in their 2IIΩ(1) and 2IIΩ(2) states have been determined. It is shown that the results are in agreement with theoretical expectation and that they confirm the band assignement proposed in a previous communication [2].

Autumnariol und Autumnariniol, zwei neue Dibenzo-α-pyrone aus Eucomis autumnalis Graeb. Nachweis einer Fernkopplung über sechs Bindungen in den magnetischen Protonenresonanz - Spektren

Abstract: From bulbs of Eucomis autumnalis Graeb (Liliaceae) autumnariol (1) and autumnariniol (4), two new substituted dibenzo-α-pyrones have been isolated. Their structures have been determined mainly using spectroscopic techniques. In the NMR. spectra of 1 and 4 and related model compounds an unusuallong-range coupling over six bonds has been demonstrated.

A Photoelectron‐spectroscopic investigation of the Homoconjugative Interaction between π‐ and Walsh‐Orbitals in endo‐ and exo‐Cyclopropano‐norbornene

Abstract: Photoelectron spectra of endo- and exo-cyclopropano-norbornene ( = endo- and exo-tricyclo[3.2.1.02.4]octa-6-ene) show that a significant homoconjugation exists between the π-orbital of the double bond and the symmetric Walsh-es-orbital of the cyclopropane ring in the exo-isomer, whereas the interaction is negligeable in the endo-derivative.

Die Phlorglucide von Dryopteris viliarii (Bell.) Woynar und anderer Farne der Gattung Dryopteris sowie die mögliche Abstammung von D. filix‐mas (L.) Schott

Abstract: The phloroglucides of the ferns of the Dryopteris filix-mas complex; ie D abbreviata, D filix-mas s str and D borreri (diploid and triploid) as well as those of D villarii, subspvillarii and subsp pallida were reinvestigated with improved semiquantitative analytical methods The phloroglucides of D aitoniana and D athamantica were examined for the first time The results (table 1) are compatible with the hypothesis, without proving it, that the allotetraploid species D filix-mas s str originated from a hybrid of D abbreviata with D villard (with subsequent doubling of its chromosomes) and the apogamous triploid D remota from D assimils with diploid D borreri, and the equally apogamous triploid D borreri from a hybrid of D abbreviata (or a related diploid sexual taxon) with diploid D borreri D aitoniana contains a large amount of trisflavaspidic acid but no filixic acid and differs in this respect from the three representatives of the D filix-mas complex

Computer‐Drawn Molecular Orbitals: An aid for the users of MO‐programs

Abstract: A computer program is described, which generates a simplified pictorial representation of computed molecular orbitals. As examples, the highest occupied MO's of the two C8-rotamers of the cyclopropylcarbinylcation (C4H7+), of pyridine and of barrelene (bicyclo[2.2.2]octatriene) are given.

Die Valenzisomerisierung des trans‐15, 16‐Dimethyl‐dihydropyrens ‐ ein beitrag zur frage nach der aktivierungsenergie symmetrie‐verbotener prozesse. Vorläufige mitteilung

Abstract: Concerted electrocyclic processes which are forbidden according to the symmetry conservation rules of Woodward & Hoffmann, may nevertheless take place at low activation energies. The necessary conditions are exemplified by the unique case of the trans-15, 16-dimethyl-dihydropyrene ⇌ 15, 16-dimethyl-[2.2]metacyclophane-4,9-diene system.

Über den Einfluss des Kontaktterms auf die Lantlianiden‐Verschiebung der NMR.‐Signale aromatischer stickstoffheterocyclen

Abstract: The inclusion of a contact term in the calculation of the paramagnetic shifts induced by Eu(tmhd3) does not Improve the predicted values.

On the correlation between photoelectron and electronic spectra in trans‐ azomethane

Abstract: A possibility of correlating electronic and photoelectron spectra is discussed, using trans-azomethane as an example. The Coulomb and exchange integrals required were obtained by three semi-empirical SCF-methods: MINDO/2, CNDO/2, and a modified CNDO method. The orbital energies were taken as minus the corresponding experimental ionization potentials. The sequence of the transition energies ΔE (ns π*) Δ E (na π*) < ΔE (π π*) is found to be different from the ionization potential sequence IP (ns) < IP (π) < IP (na), in agreement with previous spectroscopic studies; the results support the latest view that the π π* transition of the azo group occurs at around 12 eV.

Energy Profiles for Ring Formation‐ and Ring Opening‐Processes in the cis‐Stilbene‐4a,4b‐Dihydrophenanthrene System. An example of the feasibility of a process forbidden by the rules of orbital symmetry conservation

Abstract: An Extended Huckel MO treatment of the system cis-stilbene (I)-4a, 4b-dihydrophenanthrene (II) indicates that the concerted photocyclisation is a conrotatory process of the first excited electronic state. The activation energies for the photocyclisation and for the thermal ring opening and the ground state energy difference between I and II, as predicted by the present calculation, are in good agreement with the experimental findings. The observed effects of substituents on the photocyclisation quantum yields are satisfactorily accounted for by a general qualitative treatment and thus indicate that the photocyclisation takes place in the first excited state.

A strongly fluorescing abnormal chromosome in a malformed child.

Abstract: The case of a sexchromatin negative “girl” with multiple malformations is presented. A small metacentric chromosome was found to replace her second X chromosome, half of which was strongly fluorescing after staining with Quinacrinedihydrochloride, and late replicating after labelling with tritiated thymidine. The chromosome was interpreted as a translocation chromosome between the long arms of a Y and a partially trisomic autosome.