A simple model for melting curve maxima

A “shouldered” repulsive inter-atomic potential, in conjunction with a statistical mechanics perturbation theory which treats the fluid and solid phases in a consistent way, leads to a maximum in the (P, T) coexistence curve, in qualitative agreement with the melting curve of Cs.     

Molekülstruktur in der Theorie der Spinvalenz I

Zusammenfassung Wie in der Theorie der Valenzstrukturen (Kimball 1940), so kann man auch in der Theorie der Spinvalenz ohne Rechnung, d. h. nur mit den Mitteln der Gruppen- und Darstellungstheorie, zu Aussagen über die Molekülstruktur von Verbindungen des Typs ML _n kommen. Die Ergebnisse für sog. ¹ A ₁-Moleküle werden angegeben und mit denen von Kimball verglichen.

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Spin valence theory provides a basis for the group theoretical derivation of the structure of ML _n -molecules. Results for molecules in a totally symmetrical ground state are compared with predictions of the valence bond method (Kimball 1940).

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Résumé La théorie de la valence de spin permet de dériver les structures de molécules du type ML _n á l'aide de la théorie des groupes. Des résultats pour de molécules en état ¹ A ₁ (totalement symétrique) sont comparés á ceux de la méthode de mésomérie (Kimball 1940).

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Auszugsweise vorgetragen auf der Westdeutschen Chemiedozententagung, Freiburg i. Brsg., 27.–30. 4. 1964 und der 8. I. C. C. C., Wien, 7.–11. 9. 1964.     

Enzyme analysis by means of the air-gap electrode-determination of urease and arginase by monitoring of the initial reaction rate

The air-gap electrode has been used in kinetic chemical analysis, illustrated by the assay of the activities of the enzymes urease and arginase. The determinations are based on monitoring the initial reaction rates of the selective release of ammoniacal nitrogen, which in the arginine—arginase system was ensured by adding excess of urease. The reaction rates measured are in the range 2.5 · 10^-5—1.5 · 10^-3M min^-1; the relative standard deviation is ca. 2.8 %.     

Oxydative Kupplung von Indolinen und 1,2,3,4-Tetrahydrochinolinen mit Kaliumpermanganat. 153. Mitteilung über Alkaloide

It is shown that treatment of indolines like 4a-methyl-1,2,3,4,4a,9a-hexahydrocarbazole ( 1 ) and even indoline-alkaloids like 5 or 6 (cf. scheme 1) with KMnO₄ in boiling acetone solution leads to the indolenines 10, 29 and 33 , respectively, and, in relatively high yields, to N,N′- or C,N-coupling products (cf. schemes 2 and 5). The results of the oxidation of 6- or 8-methoxy-indolines are shown in schemes 3 and 4, respectively. Analogous ‘dimeric’ dehydrogenation products are observed when tetrahydroquinolines ( 8 and 9 , resp.) are treated with KMnO₄ (cf. schemes 7 and 8, resp.). The formation of the bis-compounds is almost certainly due to the coupling of two intermediate indolenyl or tetrahydroquinolyl radicals. The cleavage of the hydrazine derivatives 11 or 17 (scheme 9) also leads to ‘dimeric’ C,N-coupling products. By heating the hydrazine derivative 17 with aqueous HCl, a complete cleavage into indoline 2 and the indolenines 16 and 20 is observed. The reaction is rationalized in scheme 10. So far no naturally occurring alkaloids related to the above mentioned C,N-coupling products have been found.     

Photochemische Cycloadditionen von 3-Phenyl-2H-azirinen an Carbonsäurechloride. 35. Mitteilung über Photoreaktionen

Irradiation of 2, 3-diphenyl-2H-azirine ( 1a ) and 1-azido-1-phenyl-propene, the precursor of 2-methyl-3-phenyl-2H-azirine ( 1b ), in benzene, with a high pressure mercury lamp (pyrex filter) in the presence of acid chlorides yields the oxazoles 5a–d (Scheme 2). Photolysis of 2, 2-dimethyl-3-phenyl-2H-azirine ( 1c ) under the same conditions gives after methanolysis the 5-methoxy-2, 2-dimethyl-4-phenyl-3-oxazolines 7a, b, d , while hydrolysis of the reaction mixture leads to the formation of the 1, 2-diketones 8a, c, d (Scheme 4). The suggested reaction path for all these reactions is a 1, 3-dipolar cycloaddition of the photochemically generated benzonitrilemethylides 2 to the carbonyl double bond of the acid chlorides to give the intermediates 4 , followed by either elimination of hydrogen chloride or solvolysis (Schemes 2 and 4). Irradiation of 1c in the presence of acetic acid anhydride leads via the intermediate 9 to the 5-hydroxy-3-oxazoline 10 and the 5-methylidene-3-oxazoline 11 (Scheme 5).     

Die thermische Umlagerung von 2-(Buta-1′,3′-dienyl)-phenolen in 2-Alkyl-2H-chromene; Beispiele für aromatische [1,7a]- und [1,5s]sigmatropische Wasserstoffverschiebungen

2-(1′-cis,3′-cis-)- and 2-(1′-cis,3′-trans-Penta-1′,3′-dienyl)-phenol (cis, cis- 4 and cis, trans- 4 , cf. scheme 1) rearrange thermally at 85–110° via [1,7 a] hydrogen shifts to yield the o-quinomethide 2 (R ? CH₃) which rapidly cyclises to give 2-ethyl-2H-chromene ( 7 ). The trans formation of cis, cis- and cis, trans- 4 into 7 is accompanied by a thermal cis, trans isomerisation of the 3′ double bond in 4. The isomerisation indicates that [1,7 a] hydrogen shifts in 2 compete with the electrocyclic ring closure of 2 . The isomeric phenols, trans, trans- and trans, cis- 4 , are stable at 85–110° but at 190° rearrange also to form 7 . This rearrangement is induced by a thermal cis, trans isomerisation of the 1′ double bond which occurs via [1, 5s] hydrogen shifts. Deuterium labelling experiments show that the chromene 7 is in equilibrium with the o-quinomethide 2 (R ? CH₃), at 210°. Thus, when 2-benzyl-2H-chromene ( 9 ) or 2-(1′-trans,3′-trans,-4′-phenyl-buta1′,3′-dienyl)-phenol (trans, trans- 6 ) is heated in diglyme solution at >200°, an equilibrium mixture of both compounds (～ 55% 9 and 45% 6 ) is obtained.     

Photochemisches Verhalten von 1- und 2-alkylierten 1, 2-Dihydronaphthalinen bei tiefen Temperaturen

The irradiations of 1, 1-dimethyl- (8), 1, 1-di-(tri-deuteriomethyl)- (d₆– 8 ), 1, 1, 2, 2-tetramethyl- ( 9 ) and cis- and trans-1, 2-dimethyl-1, 2-dihydronaphthalenes (cis- and trans- 10 ) were investigated in 2, 2-dimethylbutane/pentane at ?100° using a mercury high-pressure lamp, and with mercury high- and low-pressure lamps at room temperature. The results were compared with one another, and those of the individual compounds are collected in schemes 2 and 4–7. The most important results are the following: 1. The 1, 2-dihydronaphthalenes undergo a conrotatory ring opening to the o-quinodimethanes on irradiation with high- or low-pressure lamps at room temperature or at ?100°. Thermal reactions ([1, 7a]H-shifts, electrocyclisations) are suppressed at ?100°. The o-quinodimethanes formed from 8 (scheme 2), 9 (scheme 5) or cis- 10 (scheme 6) undergo on irradiation with the high-pressure lamp, [1, 5]H-shifts or photochemical Diels-Alder reactions after renewed photochemical excitation, to yield the benzobicyclo[3.1.0]hex-2-ene derivatives. These Diels-Alder reactions do not proceed stereospecifically, and therefore are not orbital symmetry controlled reactions. 2. If the 1, 2-dihydronaphthalenes are irradiated at room temperature with either a high- or a low-pressure lamp, then the initially formed o-quinodimethanes undergo thermal [1, 7a]H-shifts, in preference to all other reactions, as long as this is sterically possible; the resulting products can undergo secondary photochemical transformations. Such o-quinodimethanes are formed on irradiation of 8, 9 and cis- 10 . From trans- 10 , an o-quinodimethane mixture is formed, of which one component (cis, cis- 22 ) undergoes thermal [1, 7a] H-shifts, while the other (trans, trans- 22 ) suffers a thermal disrotatory electrocyclisation to give cis- 10 . If a high-pressure lamp is used in the last experiment, then the competing photochemical Diels-Alder cyclisation to bicyclic compounds of the type 23 (scheme 7) can result in the trans, trans- 22 . As was shown by Salisbury [3], and confirmed by ourselves in other cases [2], photochemical Diels-Alder reactions or [1, 5]H-shifts in the o-quinodimethanes require light of wavelength ? 400 nm (high-pressure lamp). The present photochemical investigations amplify and confirm our earlier conclusions concerning the photochemistry of the 1, 2-dihydronaphthalenes [2].     

Fast resonance raman spectroscopy of short-lived radicals

We report the first application of pulsed resonance Raman spectroscopy to the study of short-lived free radicals produced by pulse radiolysis. A single pulse from a flash-lamp pumped tunable dye laser is used to excite the resonance Raman spectrum of the p-terphenyl anion radical with an initial concentration of 4 × 10^?5 moles per liter and a half life of 2 μs. The spectrum is recorded by an optical multichannel system consisting of an image intensifier coupled to a TV-camera.     

Flow injection analysis : Part VI. The determination of phosphate and chloride in blood serum by dialysis and sample dilution

The rapid determination of chloride and inorganic phosphate in blood serum based on continuous flow spectrophotometry was adapted to Flow Injection Analysis by applying dialysis as well as differential dilution of the injected samples. In addition to the manual injection procedure, an automated microsampling unit was developed and used. By continuous dialysis, chloride could be determined reproducibly at a sampling rate of 125 samples per hour at sample volumes of 60 μl or less. A similar sampling rate and high precision were obtained for the determination of inorganic phosphate by using differential dilution.     

Spektrophotometrische Messung an kleinsten Flüssigkeitsmengen

Zusammenfassung Bei jeder spektrophotometrischen Meßeinrichtung ist das Volumen aller Küvetten, die den gleichen Lichtstrom hindurchtreten lassen, proportional dem Quadrat der Küvettenlänge. Der Proportionalitätsfaktor hängt bei Filterphotometern nur von den Eigenschaften von Lichtquelle und Empfänger ab, bei Verwendung eines Monochromators außerdem von den Abmessungen des Monochromators, im wesentlichen von seinem Auflösungsvermögen. Bei handelsüblichen Spektralphotometern ist es im Grünen möglich, bei 10 cm Schichtlänge mit einem Volumen von weniger als 0,1 ml ohne Einschränkung der Meßgenauigkeit auszukommen.

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Summary In every spectrophotometric measuring device the volume of all cells, which permit the passage of the same light flux, is proportional to the square of the length of the cell. In the case of filter photometers, the proportionality factor depends solely on the characteristics of the light source and receiver; if a monochromator is used also on the dimensions of the monochromator, and essentially on its resolving powers. With the spectrophotometers on the market, it is possible in the green, when using a 10 cm path length, to get along with a volume of less than 0.1 ml without decreasing the precision of measurement.

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Résumé Dans toutes les installations de spectrophotométrie le volume de toutes les cuves qui laissent passer la même quantité de lumière est proportionnel au carré de leur longueur. Le facteur de proportionnalité dépend dans les photomètres à filtre, des propriétés de la source de lumière et du récepteur. En outre lorsqu'on utilise un monochromateur il dépend des caractéristiques de ce dernier, c'est-à-dire essentiellement de son pouvoir séparateur. Dans les spectrophotomètres du commerce on peut opérer avec une couche de 10 cm de long et un volume inférieur à 0,1 ml sans diminuer la précision de la mesure.