Preparation et proprietes physico-chimiques de l'alanate de magnesium Mg(AlH4)2

Résumé L'alanate de magnésium Mg(AlH₄)₂ désolvaté a été obtenu avec une pureté satisfaisante. La décomposition thermique a été étudiée par thermogravimétrie sous pression réduite (10^–3 torr). La capacité calorifique molaire à 298 K ainsi que l'enthalpie de formation ont été déterminées avec un microcalorimètre Calvet.C _p Mg(AlH₄)₂=32.5 cal·mol^–1·K^–1;H _fMg(AlH₄)₂=–19.2 kcal· mol^–1

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Solvent-free Mg(AlH₄)₂ has been prepared with good purity. Thermogravimetry has been used to investigate the thermal decomposition of Mg(AlH₄)₂ under low pressure (10^–3 torr). The molar heat capacity at 298 K and the heat of formation have been measured with a CALVET microcalorimeter.C _p Mg(AlH₄)₂=32.5 cal·mol^–1·K^–1 H _fMg(AlH₄)₂=–19.2 kcal·mol^–1

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Zusammenfassung Lösungsmittelfreies Mg(AlH₄)₂ wurde mit befriedigender Reinheit hergestellt. Scine thermische Zersetzung wurde durch Thermogravimetrie bei niedrigem Druck (10^–3 torr) untersucht. Die molare Wärmekapazität bei 298 K und die Bildungswärme wurden mit einem Calvet Mikrokalorimeter gemessen.C _p Mg(AlH₄)₂=32.5 cal·mol^–1·K^–1;H _f Mg(AlH₄)₂=–19.2 kcal· mol^–1

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Mg(AlH₄)₂, . Mg(AlH₄)₂ (10^–3 ) . 298 . C_pMg(AlH₄)₂=32.5 ^–1. ^–1 H _fMg(AlH₄)₂=–19.2 ^–1.

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Ce travail a été effectué dans le cadre d'un contrat de recherches passé par le Laboratoire de Chimie Minérale avec la Direction des Recherches et Moyens d'Essai. Nous remercions bien vivement cet organisme de l'aide qu'il a nous apportée.     

Catalytic cracking and dehydrogenation of butanes and neopentane on reduced copper-exchanged Y-zeolites

The activity and selectivity of reduced Cu–Y zeolites containing acidic sites either only of Brönsted or only of Lewis type suggest that the Lewis acid sites are active in the cracking of butanes and neopentane, while both Lewis acid and Lewis base sites are involved in the mechanism of the dehydrogenation of these reactants.

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Cu–Y , , , , . , .

     

Crystal and molecular structure of the sesquiterpene lactone mucrin

An x-ray structural investigation has been made of the sesquiterpene lactone mucrin, diffractometer: Cu K radiation, 942 reflections, direct method, R factor 0.083. The spatial structure of the molecule has been determined: the lactone ring is trans-linked with the germacrane ring, the epoxide group in the 1,10 position has the 1,10-orientation, and the hydroxy group in position 6 has the -orientation.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Institute of Bioorganic Chemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 59–63, January–February, 1988.     

Triterpene glycosides of Hedera taurica. III. Structures of hederosides A3, B,E2 and F from the berries of Crimean ivy

Four triterpene glycosides — hederoside A₃, B, E₂, and F — have been isolated from the berries ofHedera taurica Carr. (Crimean ivy), family Araliaceae. On the basis of the results of acid hydrolysis and physiochemical methods of investigation the following structures have been suggested: A₃ — 3-O-(-L-arabinopyranosyl)hederagenin; B — 3-O-(-D-glucopyranosyl)hederagenin; E₂ — 3-O-[O--D-glucopyranosyl-(1 2)--D-glucopyranosyl]oleanolic acid; and F — 3-O-[O--D-glucopyranosyl-(1 2)--D-glucopuranosyl]hederagenin. Hederoside E₂ is a new glycoside of oleanolic aid.M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 721–726, September–October, 1988.     

Catalytic ethoxylation of phenol and phenol derivatives

The kinetics of catalytic mono- and polyethoxylation of phenol, p-cumyl-phenol and p-isooctylphenol have been studied in the presence of strongly basic anion exchanger Wofatit SBW in hydroxy form. The influence of substituents on the rate has been investigated and the mechanism of the reaction is discussed.

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- , - Wofqtit SBW . .

     

The electronic structure of groups of isomeric hetero-aromatic systems

The electronic structure of the configurational isomers of 3-3-, 3-5- and 5-5-bis-oxadiazole, and of trans-,-di-(3-3)-, -(3-5)- and -(5-5)-diazolyl-ethylene, was studied by using the ASMO, SCF, CI procedure developed by Pariser, Parr and Pople. The total -electron energy is taken as the measure for ranging the various isomers and their different configurations in a given order of stability.Predictions based on charge distributions and bond orders are in agreement with the chemical behaviour of the known 3-3 and 5-5 isomers, and are therefore regarded as reliable also for the 3-5 compounds, not described in the literature so far.The calculated value of the lowest singlet transition energy agrees with the observed spectra, with a scatter of ±0.20 eV depending on the particular procedure chosen for calculating the _pqand (App) integrals. The calculated second singlet transition is found to depend on the procedure chosen for those integrals to such an extent as to make the prediction unreliable.

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Zusammenfassung Die Elektronenstruktur der Konfigurationsisomere von 3,3-, 3,5- und 5,5-bis-Oxadiazol und trans-,-di-3,3-, -3,5- und -5,5-Diazolyläthylen wurde mit Hilfe der ASMO-SCF-CI-Methode studiert. Die totale -Elektronenenergie wurde als Maß für die Stabilität der verschiedenen Isomere und ihrer Konfigurationen gewählt.Voraussagen, die auf Ladungsverteilungen und Bindungsordnungen basieren, sind in Übereinstimmung mit dem chemischen Verhalten der bekannten 3,3- und 5,5-Isomere und wurden deshalb auch als zuverlässig für die 3,5-Verbindungen angesehen, die bis jetzt in der Literatur nicht beschrieben sind.Der berechnete Wert für die niedrigste Singulett-Anregungsenergie stimmt mit den beobachteten Spektren bis auf ±0,2 eV überein, abhängig von der Berechnungsart für die _pqund (App). Die Anregungsenergie für den zweiten Singulettübergang läßt sich in diesem Rahmen nicht vorhersagen.

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Résumé La structure électronique des isomères configurationales des 3-3-, 3-5- et 5-5-bis-oxadiazole, et des trans---di-(3-3)-, -(3-5)- et -(5-5)-diazolyl-ethylène a été étudiée par la méthode ASMO, SCF, CI sélon la forme développée par Pariser, Parr et Pople. L'énergie totale des électrons a été prise comme étalon pour classifier les isomères et leurs differentes configurations sélon un ordre de stabilité.Les déductions que l'on peut tirer de la distribution des charges et des ordres de liaison sont en accord avec les observations chimiques des isomères connus, 3-3 et 5-5; par conséquent on peut considérer raisonables les prédictions que ont été faites sur les isomères 3-5, qui ne sont pas décrites dans la literature jusqu'ici.La valeur calculée pour la première transition de singulet est en bon accord avec le spectre d'absorption observé, l'incertitude due à la procedure choisie pour les integrales _pqet (App) étant ±0.20 eV. La deuxième transition de singulet apparait dépendre presque entièrement de la choix faite pour les dites integrales.

     

Oxidative side chain cleavage in the reaction of 20-hydrazones of Δ5-pregnenetiol-3β, 16α, 17α-one-20-16-acetates with leadtetraactate

Conclusions Oxidative cleavage of the side chain takes place in the reaction of 20-hydrazones of steroid 16, 17-dihydroxy-ketone 16-acetates with lead tetraacetate, leading to the formation of 16-acetoxy-17-ketones.See [1] for Communication 23.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 163–164, January, 1970.     

The hydrolytic stability of the three-membered ring of alkyl- and alkoxy-β-(ethyleneamino)ethylsilanes

Conclusions The hydrolytic stability of the ethyleneimine ring in trialkyl- and trialkoxy--(ethyleneamino) ethylsilanes in aqueous media has been studied and the possibility of obtaining organosiloxanes containing the three-membered ethyleneamine ring in the-position to the silicon atom has been shown.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1129–1132, May, 1969.     

Spectrophotometric investigation of rhenium-dimethylglyoxime complex in solution

Summary By applyingAsmus's straight-line method it was found that the rhenium-dimethylglyoxime complex formed in hydrochloric acid solution has a metal to oxime ratio of 12. whereas the one formed in acetic acid solution has a 13 ratio. The dissociation constant of the former is 1·10^–6, and that of the latter 2.3·10^–9.

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Zusammenfassung Mit Hilfe der Geradenmethode vonAsmus wurde das Metall Oxim-Verhältnig der Rhenium-Dimethylglyoxim-Komplexe in salzsaurer Lösung zu 12, in methanolisch-essigsaurer Lösung dagegen zu 13 gefunden. Die Dissoziationskonstanten betragen 1·10^–6 für den ersten, 2,3·10^–9 für den zweiten Komplex.

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Alexander v. Humboldt Fellow.     

Evaluation of energy distribution on a heterogeneous surface from heat of adsorption and its application to the ammonia/Na-Y zeolite system

The— function (energy level function) which represents surface heterogeneity was derived from theq— function (experimental heat function) in the case of reversible adsorption. The Langmuir equation was extended and applied to the procedure of calculations. An iterative calculation led to the most probable— function by setting theq— function and adsorption temperature. As an example for actual cases, the— function of Na-Y zeolite was calculated from theq— function obtained by the measurement of heats of adsorption of ammonia at 373 K. The— function thus derived seemed to be consistent with the positional distribution of sodium ions.     

Triterpene glycosides ofPatrinia intermedia

Conclusions It has been established that patrinoside C₁ is -D-xylopyranosido(1 2)--D-glucofuranosido(1 3)--L-rhamnopyranosido(1 3)oleanolic acid.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 1, pp. 22–26, 1969     

Variations in the cooling transitions of potassium nitrate

Because of questions concerning the suitability of potassium nitrate as a dynamic temperature standard for DTA, the relation between the experimental procedure and the resulting curves was ascertained for the Standard Reference Material KNO₃. The material behaves differentlyon cooling in open pans than in cylindrical holders because confinement in the latter case initiates reversion to the room temperature form. Under the conditions of use as a dynamic temperature reference material, the curves are accurately reproducible.

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Zusammenfassung Zur Überprüfung der Eignung von Kaliumnitrat als dynamische Temperatur-Eichsubstanz für die DTA, wurde der Zusammenhang des Versuchsvorganges und der erhaltenen Kurven für das Standard-Referenz-Material KNO₃ untersucht. Die Substanz verhält sich bei der Kühlung in offenen Tiegeln und in zylindrischen Behältern unterschiedlich, da in letzteren die Begrenztheit die Reversion zur Zimmertemperatur-Form in Gang setzt. Unter den für das dynamische Temperatur-Referenz-Material gegebenen Bedingungen sind die Kurven gut reproduzierbar.

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Résumé En raison de l'emploi du nitrate de potassium comme étalon de température en ATD, on a étudié l'influence des conditions d'expérience sur les courbes obtenues. Le comportement de ce corps est différent si on effectue le refroidissement dans des capsules ouvertes ou dans des creusets cylindriques. Dans ce dernier cas, le manque d'espace initie le retour à la forme stable delà température ambiante. Dans les conditions d'emploi comme matériau de température étalon, les courbes sont exactement reproductibles.

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. - , , .

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One of us is indebted to the U. S. National Science Foundation for support of part of this study.     

Synthesis of styryl-substituted 2-phenyl- and 1,2-diphenylcyclopenta[b]-chromenes

A number of styryl derivatives that are capable of undergoing formylation and acylation at the side CH=CH group were obtained from 1,2-diphenyl-3-formyl- and 2-phenyl-1,3-diformylcyclopenta[b]chromene by means of the Wittig reaction. It was observed that the Wittig reaction is structurally selective for 2-phenyl-1,3-diformylcyclopenta [b] chromene; the reaction proceeds only at the aldehyde group in the 3 position. Sulfuration of 2-phenyl-1,3-distyrylcyclopenta[b]chromene with sulfur leads to the formation of a new system —benzo[2,3]thiepino[4,54,5]cyclopenta[b]chromene. A significant bathochromic effect of the styryl groups on the electronic spectra of the cyclopentachromenes was noted.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1324–1328, October, 1978.     

Triterpene glycosides of Astragalus and their genins. XXIV. Cycloorbicoside G from Astragalus orbiculatus

A bisdesmosidic glycoside — cycloorbicoside G — has been isolated from the epigeal parts of the plantAstragalus orbiculatus Ledeb. (Leguminosae), and on the basis of chemical transformations and spectral characteristics its structure has been established as (23R,24S)-16,23;16,24-diepoxycycloartane-3,7,25-triol 25-O--D-glucopyranoside 3-O--D-xylopyranoside.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 837–842, November–December, 1987.     

Sinapoyl ester of glucoerysimoside inErysimum marschallianum

Summary A new cardenolide glycoside — sinapoylglucoerysimoside — having the structure of strophanthidin 3-0-[0-sinapoyl--D-glucopyranosyl-(14) 0--digitoxopyranoside — has been found in the seeds ofErysimum marshallianum.Kiev Institute for the Further Training of Doctors. Translated from Khimiya Prirodnykh Soedinenii No. 5, pp. 603–606, September–October, 1975.     

Triterpene glycosides of Gypsophila trichotoma III. Structure of trichoside B

Summary The structure of trichoside B — a gypsogenin tetraoside fromGypsophila trichotoma Wend. — has been established. The glycosidic carbohydrate chain is O--D-glucopyranosyl-(1 3)-O--D-glucuronopyranosyl and the acyloside chain is O--D-glucopyranosyl-(1 4)-O--D-galactopyranosyl.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 431–434, July–August, 1971.     

Steroids of the spirostan and furostan series from plants of the genus Allium. XXV. Structure of anzurogenin B from Allium suvorovii and Allium Stipitatum

A new genin of the spirostan series — anzurogenin B having the structure of 2,5-epoxy-(25R)-spirostan-3,6-diol — has been isolated form the collective fruit of the cocultivatedAllium suvorovii Rgl. andAllium stipitatum Rgl. (family Liliaceae).Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 218–221, March–April, 1988.     

Influence of silica on the properties of evaporated V?Mo oxide catalysts

According to⁵¹V-NMR studies of the state of vanadium ions in parent solutions and in catalysts, evaporated V–Mo oxide catalysts are shown to be more active and selective in acrolein oxidation to acrylic acid than unsupported samples.

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- , , , . e₁V .

     

Phytoecdysones ofRhaponticum integrifolium II. Integristerone A

Summary A new phytoecdysone — integristerone A — has been isolated from the flower heads ofRhaponticum integrifolium. It has been shown that it is 1,2,3,14,20R,22R,25-heptahydroxy-5-cholest-7-en-6-one.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 813–819, November–December, 1977.