Preparation of an amphiphilic resin-supported BINAP ligand and its use for rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid in water

[reaction: see text] The axially chiral bisphosphine ligand, 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (binap), was supported on a polystyrene-poly(ethylene glycol) copolymer (PS-PEG) resin and was used successfully for the rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid to alpha,beta-unsaturated ketones in water.     

Simultaneous determination of eleven dyes and their aluminum lakes in drugs

A 3-step extraction method was developed for the simultaneous determination of 11 dyes and their aluminum lakes in drugs. The dyes were first extracted with warm water (approximately 60 degrees C) and were cleaned up by solid-phase extraction with a tC18 cartridge. Aluminum lake dyes that remained in the precipitate were extracted with 0.02M NaOH. Aluminum in the dye lakes was reextracted into the organic layer with acetylacetone-butyl acetate (1 + 9, v/v), as an acetylacetone chelate, and was quantified by atomic absorption spectrometry. The dye portions of the aluminum lakes remained in the aqueous layer and were cleaned up in the same way as the dyes. The dyes and the dye portions of the aluminum lakes were quantified by ion-pair liquid chromatography with a photodiode array detector within 20 min. The recoveries of dyes from drug fortified at 10 microg of each dye per pill were 87.0-102.2%, and the recoveries of dyes from drugs fortified at 50 microg of each dye lake per pill were 82.9-101.6%, except for recoveries of indigo carmine. In 40 ethical and over-the-counter drugs, dyes that were not indicated in the package insert information for drugs were detected in 5 samples. The highest amount of dye found in a drug was 1169.5 microg erythrosine, which was detected in a capsule of antibiotic. Aluminum lake dyes were detected in 8 samples of various dosage forms.     

A convenient method for the preparation of inverted tert-alkyl carboxylates from chiral tert-alcohols by a new type of oxidation-reduction condensation using 2,6-dimethyl-1,4-benzoquinone

Oxidation-reduction condensation using in situ-formed alkoxydiphenylphosphines, 2,6-dimethyl-1,4-benzoquinone, and carboxylic acids provided a new and efficient method for the preparation of inverted tert-alkyl carboxylates from various chiral tertiary alcohols.     

Mo- and Vb-benzene characters : Analysis of the “clar's aromatic sextet” in polycyclic aromatic hydrocarbons

In order to analyse the mode of distribution of π-electrons in a given hexagon in a polycyclic aromatic hydrocarbon, normalised VB- and MO- (HMO and PPP) benzene characters are defined and calculated for a number of molecules. Their relation to the topological structure of the molecule was studied in detail. By combining these quantities it was shown that the π-electrons in the three different classes (primary, secondary and tertiary) of hexagons have different distribution over the benzene ring. It was found that the value of the benzene character is determined by the local topological structure up to the third next hexagons. These findings qualitatively support and quantitatively figure out the concept of the Clar's aromatic sextet, which can be interpreted as the “higher order π-electronic correlation” that the π-electronic system of polycyclic aromatic hydrocarbons can be described by the cooperative interaction of the units of closely correlated six π-electrons.     

Calibration of the isomer shift of121Sb and119Sn by means of Mössbauer spectroscopy and molecular orbital calculation

The relationship between the isomer shifts in Mössbauer spectroscopy and the electron contact densities has been investigated for several antimony and tin compounds. Mössbauer spectra for¹²¹Sb in rapidly frozen solutions of antimony compounds were measured. The isomer shifts are compared with the valence electron densities at the antimony nucleus calculated with theab initio molecular orbital method. The relative difference of the nuclear charge radius ΔR/R could be obtained as ΔR/R =?(10.2±1.0)×10^?4 for the 37.15 keV M1 transition of¹²¹Sb. Further, some computations of the electron density at the tin nucleus for several tin compounds were performed. By comparing the valence electron contact densities with isomer shifts, which had been reported for several tin compounds in rare-gas matrix states, the value of ΔR/R for 23.87 keV M1 transition in¹¹⁹Sn was estimated to be (1.57±0.03)×10^?4.     

Another new application of standard-addition technique in flame spectrophotometry

Summary A new flame-photometric method of determination, the Double-Coefficient Method, based upon the standard-addition technique has been proposed.The method is found to be useful for samples where a concomitant may seriously interfere with the radiation intensity of the specified substance. No knowledge about sample composition is needed and the only prerequisite to the method is the log-log translation rule which has been generally valid when alkali metals are specified and concomitants cause multiplicative interference. In other words, the method is generally applicable where the concomitant C–I curve is expressed in a formI ^* = n· f_(m·c) in which I^* is the intensity recorded,C is the concentration of specified substance,I = f_(C) is the expression for the specifiedC- I curve andm andn are constants which need not be known.Many determinations of NaCl have been carried out with various interfering concomitants. In only exceptional cases did the relative error exceed 10% no matter how much interference there was from concomitants.It is suggested that some investigation into the dependence of the logC– logI relation on various excitation conditions, and some method of controlling theC-I function would be of great interest and practical value. In some special case the Double-Coefficient Method needs only a very simplified procedure.

---

Zusammenfassung Eine neue flammenphotometrische Bestimmungsmethode wird vorgeschlagen. Diese Doppel-Koeffizient-Methode beruht auf der Zugabe von Standard-Substanzen und erwies sich als geeignet für Proben, in denen eine Begleitsubstanz die Strahlungsintensität des zu bestimmenden Elementes wesentlich beeinflußt. Keinerlei Kenntnis der Zusammensetzung der Probe ist nötig. Die einzige Vorbedingung des Verfahrens ist das Gesetz der log-log-Übertragung, das allgemein für die Bestimmung von Alkalimetallen neben multiplikativ störenden Begleitsubstanzen gültig ist. Mit anderen Worten, die Methode ist allgemein dort anwendbar, wo dieC-I-Kurve der Begleitstoffe durch die BeziehungI ^* =n · f_(m·.C) ausdrückbar ist; darin steht I^* für die beobachtete Intensität,C für die Konzentration des zu bestimmenden Elementes,I = f_(C) gilt für dieC-I-Kurve des zu bestimmen- den Elementes, m undn stellen Konstanten dar, deren Wert nicht bekannt zu sein braucht.Zahlreiche Bestimmungen von NaCl wurden neben verschiedenen störenden Begleitstoffen ausgeführt. Nur in Ausnahmefällen und unabhängig von dem Ausmaß deren störender Wirkung überschritt der Fehler 10%.Die Untersuchung der Abhängigkeit des logC - logI-Verhältnisses unter verschiedenen Anregungsbedingungen sowie eine Überprüfung derC- I-Funktion wäre von großem Interesse und praktischem Wert. In einzelnen, besonders gelagerten Fällen bedarf die Doppel-Koeffizient-Methode nur einer sehr vereinfachten Arbeitsweise.

---

Résumé On a proposé une nouvelle méthode de dosage par photométrie de flamme, la méthode du double coefficient, fondée sur la technique d'addition d'un échantillon-type. On a trouvé que cette méthode était utile pour l'analyse des échantillons dans lesquels la présence d'une substance concomitante était susceptible d'altérer de façon importante l'intensité de radiation de la substance étudiée. Il n'est pas nécessaire de connaître la composition de l'échantillon, il suffit de connaître au préalable la règle de translation log-log qui est généralement valable lorsque la substance étudiée est un métal alcalin et que les substances concomitantes donnent lieu à des erreurs multiples. En d'autres termes, la méthode est généralement applicable lorsque la courbeC-I de la substance concomitante s'exprime sous la forme I^* =n · f_(m·.C) dans laquelle I^* est l'intensité enregistrée,C est la concentration de la substance étudiée,I = f_(C) est l'expression de la courbeC-I pour la substance étudiée etm etn des constantes qu'il n'est pas necessaire de connaître.De nombreuses déterminations de NaCl ont été effectuées en présence de diverses substances concomitantes gênantes. Ce n'est que dans des cas exceptionnels que l'erreur relative s'est élevée au-dessus de 10%, indépendamment de l'importance des perturbations apportées par les substances concomitantes.On propose de rechercher l'influence de certaines conditions d'excitation sur la relation logC-logI et d'établir une méthode de contrôle de la fonctionC-I, qui seraient d'une grande valeur pratique. Dans quelques cas particuliers la méthode du double coefficient ne nécessite qu'une technique très simplifiée.

     

Determination of a response function of a thermocouple using a short acoustic pulse

This paper reports on an experimental technique to determine a response function of a thermocouple using a short acoustic pulse wave. A pulse of 10 ms is generated in a tube filled with 1 bar helium gas. The temperature is measured using the thermocouple. The reference temperature is deduced from the measured pressure on the basis of a laminar oscillating flow theory. The response function of the thermocouple is obtained as a function of frequency below 50 Hz through a comparison between the measured and reference temperatures.     

Asymmetric organocatalytic oxy-Michael addition of alcohols to α,β-unsaturated aldehydes

A 1,4-addition of alcohols to α,β-unsaturated aldehydes was found to be efficiently promoted by biphenyldiamine-based catalyst 3 without formation of the acetals. An asymmetric variant of this reaction has also been performed by designing a novel axially chiral organocatalyst (R)-10c.