Flavonoids ofGnaphalium uliginosum

The herb low cudweed has yielded for the first time a new acylated flavone glycoside, for which the structure of 3,4,5,7-tetrahydroxy-6-methoxyflavone 7-O-(6-O-caffeyl--D-glucopyranoside) has been established. In addition, 6-methoxyluteolin, 6-hydroxyluteolin 7-O--D-glucopyranoside, and scutellarein 7-O--D-glucopyranoside have been isolated. Identification was made on the basis of UV, IR, PMR, and mass spectra, the products of alkaline and acid hydrolyses, and the results of elementary analyses, melting points, and specific rotations.Vitebsk State Medical Institute, All-Union Scientific-Research Institute of Medicinal Plants, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 483–487, July–August, 1979.     

Reaction of 2-substituted 4,4-dimethyl-5-methylene-1,3-dioxolanes with dichlorocarbene and certain transformations of adducts obtained

A series of derivatives of 4,4-dimethyl-5-methylene-1,3-dioxolane has been synthesized, and their reaction with dichlorocarbene, obtained under interphase catalysis conditions, has been studied. The adducts obtained undergo thermal isomerization into dichloroethylidene derivatives.     

Analysis of influence of spin relaxation on form of nuclear magnetic resonance spectra in liquids with radiofrequency pumping

For a model system of two nonequivalent nuclei with spin 1/2, the NMR spectrum of one of the nuclei has been calculated under conditions of pumping of the second spin, and a study has been made of the spectral transformation upon changing the times of transverse and longitudinal relaxation of both spins. It has been established that the form of the spectrum undergoes qualitative changes. An increase in the rate of transverse relaxation not only broadens the observed lines, but simultaneously changes the character of motion of the spins in the pumping field: With increasing relaxation rate, the motion is converted from coherent motion (nutation) to incoherent motion (transitions between levels, saturation effect). Transformations of the spectrum are related specifically to these changes.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 4, pp. 436–443, July–August 1987.     

Z/E PHOTOISOMERIZATION OF UROCANIC ACID*

The E ? Z photoisomerization of the title compound (UA) (a naturally occurring sunscreen) has been studied in aqueous solution. At a UA concentration of 6mM and using 313nm excitation, φ_E→z= 0.52, φ_Z→E= 0.47 and the photostationary state is 34% E. Under these conditions, loss of UA is minimal. Low energy triplet quenchers fail to impede the isomerization, but the reaction can be induced by several triplet sensitizers. The E_T for UA is estimated to be approximately 55 kcal/mol.     

Proper determination of order of reactions by thermal analysis

The relationship 1– _m=1.062n ^1/1–n , well-known in non-isothermal kinetics and applied for determination of the kinetic exponentn, is not universal. A more accurate modification of the given equation is proposed in the form of a more complex function 1– _m=(n, X_m), whereX _m =E/RT _m is the dimensionless Arrhenius' criterion.     

Zur Farbreaktion der Naphthole und Naphtholsulfos?uren mit 4-Aminoantipyrin

Zusammenfassung Die photometrische Methode zur quantitativen Bestimmung der Phenole mit 4-Aminoantipyrin wurde auf Naphthole und einige Naphtholsulfosäuren ausgedehnt. Die 1-Naphtholsulfosäuren geben in wäßriger Lösung eine beständige Rotfärbung, die Reaktion folgt bis zu einer Konzentration von 10 g/ml dem Beerschen Gesetz. Bei der 2-Naphtholreihe kann man die Methode nur bei 2-Naphthol und 2-Naphthol-8-sulfosäure anwenden. In den Fällen wo der gebildete Farbstoff in Chloroform löslich ist, wird durch Überführung in die organische Phase die Empfindlichkeit der Methode etwa 10fach gesteigert.     

Pyrene dimerization into 1,1′-dipyrenyl

Treatment of pyrene and some its derivatives with Cu(II) tetrafluoroborate or perchlorate in CH₃CN cleanly led to the formation of 1,1′-dipyrenyls. The other polycyclic hydrocarbons (anthracene, perylene) under the same conditions provide cation-radicals. 1,1′-Dipyrenyl strongly differs from pyrene in the chemical behavior: it does not undergo either formylation by Vilsmeier reaction, neither acylation (AcCl, ZnCl₂) or nitration (by pyridinium nitrate in boiling pyridine whereas the pyrene is easily involved into these reactions.     

Effect of 2,2,6,6-tetramethyl-1-piperidinyloxy nitroxide substituent on kinetic parameters of pseudoliving polymerization

The main kinetic and thermodynamic parameters of the pseudoliving radical polymerization of styrene mediated by 4-linoleamido-2,2,6,6-tetramethyl-1-piperidinyloxy have been studied. It has been shown that the introduction of the said substituent into nitroxide leads to a marked reduction in the rate constant of reinitiation that is compensated for by the simultaneous reduction in the rate constant of reversible termination. As a result, the rate of pseudoliving polymerization, the rate of molecular mass growth, and the polydispersity of the polymer appear to be practically the same for processes mediated by both unsubstituted and substituted nitroxides.     

Methane conversion with carbon dioxide on nickel aluminides

The catalytic activity of several samples based on nickel aluminides in methane conversion with carbon dioxide was studied. Nickel aluminides were prepared by the method of self-propagating high-temperature synthesis. The Ni₃Al system containing the nickel metal phase exhibited high activity at temperatures above 1073 K. The systems based on Ni₂Al₃ and NiAl only containing intermetallic compound phases were inactive.