Preparation of Chlorodimenthylphosphine

Krause, H. W.; Kinting, Annegret

doi:10.1002/prac.19803220322

Cited by 23 publications

(21 citation statements)

References 2 publications

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“…I t might be said much more about this approach and its validity (cf. ROBERTS andSOWARD 1974, KRAUSE andROBERTS 1976) but the present paper will only demonstrate its consequence for the PRANDTL number. Possible agreement with or contradiction to the observations should be interesting enough to be used in the over-all discussion of the limits of SOCA.…”

mentioning

confidence: 52%

A Second‐order Correlation Approximation for Thermal Conductivity and Prandtl Number of Free Turbulence

Eschrich

Rüdiger

1983

Astron Nachr

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By means of a linearizing approximation we determine the scalar thermal eddy conductivity XT in its dependence on the spectral function of the (given) turbulence and the microscopic conductivity x. The discussion of the profile x&) reveals the importance of the shape of the frequency spectrum of the velocity fluctuations. Spectra which decrease with increasing frequency produce eddy conductivities which decrease with increasing x. A distinct peak in the frequency spectrum corresponds to a non-trivial maximum of the XT-profile. These general findings are confirmed by examples some of which are numerical. Very small molecular diffusivities generally lead to a turbulent PRANDTL number of 0.4 in rough accordance whith most of the measurements. For large diffusivities, however, the turbnlent PRANDTL number bchavcs inversely to the molecular PRANDTL number. We have to doubt thiis the general belief that eddy conductivity a l w a y s exceeds eddy viscosity. For the effective PRANDTL number of the Sun w e find an upper limit of 0.3. An application of our thcnry to the smallscale motions in the uppcr Earth corc picltls valucs of 0.4. Mittels Linearisierung wird die skalare turbulente Temperaturleitfahigkeit XT in ihrer Abhangigkeit von Spektralfunktionen (der Turbulenz) und der molekularen Leitfahigkeit x bestimmt. Das Profil X T ( X ) hangt wesentlich van der Gestalt des Frequenzspektrums ab. Monoton fallende Spektren erzeugen monoton fallende Profile XT(X). Ein ausgebildetes Maximum im Spektrum findet sich dagegen als Maximum von XT bei cinem gewissen % wieder. Numerische Rechnungcn bestitigen dieses allgemeine Resultat. Fur sehr kleine molekulare Diffusivitaten crhalten wir far die turbulentc PRANDTL-Zahl den Wert 0.4 in ungefahrer Ubereinstimmung mit den Messungen. I m gegenteiligen Falle geht die turbulente PRAiVDTL-Zahl dagegen mit dem Kehrwert der molekularen PRANDTL-ZahI. Wir bezweifeln folglich die dlgemeinc Ansicht, daB die turbulente PRANDTL-Zahl i m m e r kleiner ist als Eins. Anwendung der Theorie auf die Granulation der Sonnc fuhrt auf eine cffckitvc PRANDTL-Z;LhI von ctwa 0.3, wahrend im oberen Erdkern der Wcrt 0.4 zustandig sein sollte. MotivationSince the hydrodynamic models of stellar convective zones become more and more complex, we are forced to know also those parameters which couple the various equations. This mainly concerns the PRANDTL number which links up the heat equation with the NAVIER-STOKES momentum equation. Current calculations in solar hydrodynamics demonstrate the importance of the original PRANDTL number as the ratio between kinematic viscosity and temperature conductivity. I t is rather striking, however, that there is no agreement about the actual value of this quantity whose microscopic value for the Sun is of order I O -~ (ED-MOXDS 1957). Yet the general discussion suggests values between 0.01 and I which are adopted for various (numerical) calculations. While MASSAGUER and ZAHN (1980) give arguments for the quite low value of 0.01, the papers of BELVEDERE, PAT ERN^ and STIX (1980) ...

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confidence: 52%

A Second‐order Correlation Approximation for Thermal Conductivity and Prandtl Number of Free Turbulence

Eschrich

Rüdiger

1983

Astron Nachr

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“…[15] This method also performs very well for the preparation of 2-hydroxy-substituted dibenzophosphole oxides (7'; Scheme 4). After bromine/lithium exchange on the dibromobiphenyl derivative shown in Scheme 4, the di- [16] The resulting dibenzophospholes were oxidized in situ with H 2 O 2 and the tert-butyldimethylsilyl (TBS) group was removed by reaction with tetra-n-butylammoni-um fluoride (TBAF). Both oxides 7'a (R = Ph) and 7'b (R = l-menthyl) were obtained in 75 % total yield over three steps.…”

Section: Resultsmentioning

confidence: 99%

“…This method also performs very well for the preparation of 2‐hydroxy‐substituted dibenzophosphole oxides ( 7′ ; Scheme ). After bromine/lithium exchange on the dibromobiphenyl derivative shown in Scheme , the dilithiated intermediate was treated with either PhPCl 2 or ( L ‐ menthyl)PCl 2 16. The resulting dibenzophospholes were oxidized in situ with H 2 O 2 and the tert ‐butyldimethylsilyl (TBS) group was removed by reaction with tetra‐ n ‐butylammonium fluoride (TBAF).…”

Section: Resultsmentioning

confidence: 99%

Heterohelicenes with Embedded P‐Chiral 1H‐Phosphindole or Dibenzophosphole Units: Diastereoselective Photochemical Synthesis and Structural Characterization

Yavari

Retailleau

Voituriez

et al. 2013

Chemistry A European J

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The oxidative photocyclization reactions of olefins that contain 1H-phosphindole or dibenzophosphole substituents have been applied to the synthesis of P/N-bi-heterosubstituted dimeric helicenes, as well as of new [6]- and [8]phosphahelicenes. In these photocyclization processes, the configuration of the stereogenic phosphorus center dictates the sense of helical chirality. Thus, by starting from enantiomerically pure P-menthylphosphole-oxide units, this method affords enantiopure helical compounds. The helical phosphine oxides were characterized by X-ray diffraction. After reduction of the phosphine-oxides, the corresponding helical phosphines have been used as ligands in transition-metal complexes. The X-ray crystal structure of a gold chloride complex of a [6]helicene is reported.

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“…Indeed, the simplest helical turbulence is generally reflected by where, in accordance with BOCHNERS theorem (cf. KRAUSE andROBERTS 1973, KRAUSE andRADLER 1980). The resulting expression, clearly shows that the symmetry of the indices i and j is distorted due to helicity.…”

Section: The Eddy Conductivity Tensormentioning

confidence: 99%

On Turbulent Heat Transport in Rotating Convective Zones

Rüdiger

1982

Astron Nachr

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This paper analyses the tensorial aspect of heat conduction which certainly becomes important for gravitationally stratified and rotating turbulent media. The structure of the eddy conductivity tensor is indeed a non-trivial one for turbulences with correlation times not too short in comparison with the rotation period. Since this situation may be realized in the solar convection zone, a more complex formulation of solar heat-flux problems is required rather than that with a scalar heat conductivity. We still neglect here all other energy transporters, i.e. radiation and meridional circulation, and treat a solar heat-flux problem with a heuristic mean-field ansatz of the eddy conductivity tensor. Its rotationally created latitude dependence always leads to a pole-equator surface temperature difference, which proves to be negligibly small, however, if realistic assumptions for the outward decrease of density and correlation time are involved. As a final rough estimation shows, this screening effect of the outer radiating surface should work for all late-type stars of the main sequence hence a "differential temperature" (in analogy to "differential rotation") should not be expected for those stars.Diese Arbeit diskutiert insbesondere den tensoriellen Aspekt der Warmeleitfahigkeit, der fur geschichtete und rotierende turbulente Medien Bedeutung erlangt. Der turbulente Temperaturleitfahigkeitstensor besitzt immer dann eine nichttriviale Struktur, wenn die Korrelationszeit des Turbulenzfeldes nicht sehr kurz ist gegen die Rotationsdauer des Sterns. Weil diese Situation fur die Konvektionszone der Sonne gegeben ist, benotigen entsprechende Energietransportberechnungen mehr als nur die Kenntnis einer skalaren Temperaturleitfahigkeit. Wir demonstrieren dies anhand eines heuristischen Ansatzes fur den Leitfahigkeitstensor, wobei andere Energietrager wie Strahlung und Str6mung zunachst noch vernachlitssigt werden. Die von der Rotation eingebrachte Breitenabhangigkeit der Tensorkomponenten erzeugt stets auch eine Breitenabhangigkeit der Oberflachentemperatur, welche aber fur realistische Tiefenabhangigkeiten von Korrelationszeit und Dichte extrem gering wird. Eine abschliefiende Abschatzung liefert ahnliche Verhaltnisse auch fur andere Sterntypen, so daB eine , ,differentielle Helligkeit" (analog zur , ,differentiellen Rotation") entlang der Hauptreihe eigentlich nicht zu erwarten ist.

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Preparation of Chlorodimenthylphosphine

Cited by 23 publications

References 2 publications

A Second‐order Correlation Approximation for Thermal Conductivity and Prandtl Number of Free Turbulence

A Second‐order Correlation Approximation for Thermal Conductivity and Prandtl Number of Free Turbulence

Heterohelicenes with Embedded P‐Chiral 1H‐Phosphindole or Dibenzophosphole Units: Diastereoselective Photochemical Synthesis and Structural Characterization

On Turbulent Heat Transport in Rotating Convective Zones

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