Rearrangement of allyl thienyl sulfides to allylthiophenethiols

It is shown that the rearrangement of allyl 2-thienyl and allyl 3-thienyl sulfides in various solvents at 89–136°C gives the corresponding allylthiophenethiols, which can subsequently undergo transallylation with the starting sulfide and cyclization to thienodihydrothiopyrans and methyldihydrothienothiophenes. The energy of activation of the rearrangement of both isomeric sulfides is 19 kcal/mole. The pK_a values of thiophenyl and some thiols of the thiophene series were determined, and it was established that the acidities of the allylthiophenethiols do not have a decisive effect on their ability to undergo cyclization.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 186–189, February, 1978.     

Polychloroprene rubbers used for adhesives: a small angle X-ray scattering preliminary investigation under stretching

Summary Three types of polychloroprene rubbers (Du Pont de Nemours Co. Neoprenes AD, WHV and W) used for adhesives and having different crystallization rates have been investigated.The mechanical properties of the Neoprenes samples were determined and the films were examined under stretching by SAXS for a preliminary investigation on their different superreticular order.

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Zusammenfassung Drei Typen von Polychloropren-Kautschuk mit verschiedener Kristallisationsgeschwindigkeit (Neoprene AD, WHV und W von Du Pont de Nemours), die als Klebemittel dienen, wurden als gedehnte Filme mechanisch und röntgenographisch (SAXS) untersucht. Sie zeigen Unterschiede in der Überstruktur.

     

Electro-optic scattering from nitrocellulose solutions

Measurements have been made of the light intensity scattered from dilute solutions of a sample of nitrocellulose ($\text{M}{}_{\mathrm{w}}\text{= 460,000}$) in acetone, both in the absence and presence of a.c. and d.c. electric fields. In an earlier study, owing to a mathematical slip and a false interpretation of an experimental parameter, other workers [5] interpreted similar measurements in terms of a freely rotating polar chain model. It is shown herein that this cannot be so and that the molecules of nitrocellulose of this order of molecular weight and in this type of solvent are better regarded as extremely stiff and extended.     

Organosilicon compounds VI. The preparation of silylaziridines and silyldiaziridines by silicon-carbon cleavage

The preparation of several 2-furyl-, 2-thienyl-, benzyl-, and allylsubstituted silanes is reported. Such derivatives, when treated with aziridine in the presence of a metal catalyst, afford good yields of silylaziridines and silyldiaziridines. A qualitative study of electronic and steric requirements of the displacement reaction is reported.     

A kinetic approach to homogeneous Ziegler type polymerization. Steady state

In this paper we present a kinetic approach to the analysis of steady-state homogeneous Ziegler-Natta polymerization activity data. The influence of the number of monomeric species that are coordinated to the active site on the apparent rate law is discussed and the equations are fitted to the experimental results.     

Alkylation of β-diketones through their co(II), co(III) and zn(II) complexes. 1-Bromoadamantane as alkylating agent.

α-(1-adamantyl)-β-diketones are now accessible by the alkylation of Co(II) complexes of β-diketones with 1-bromoadamantane. The intermediacy of adamantyl cation is proposed. Co(II), Co(III) and Zn(II) complexes of pentane-2,4-dione react with alkyl halides precursors of stabilized carbenium ions, to give 3-alkylpentane-2,4-diones.     

On the wigner-kirkwood coordinate probability distribution of an asymmetric anharmonic oscillator; an addendum

In a recent publication we calculated the Wigner—Kirkwood coordinate distribution function for a symmetric single- or double-well anharmonic oscillator. By a simple transformation, the results are generalized for an asymmetric anharmonic oscillator.     

The propensity rules re-examined: Evidence for a long-lived complex in alkali diatomic-rare-gas collisions

When ΔJ =±1 collision-induced transitions in Π states of excited alkali diatomics are examined over a wide range of pressures several curious phenomena are observed. With the heavier rare gases we find that the ± propensities reverse as pressure increases, and the circular polarisation of the parent line first decreases, with increasing pressure and then begins to rise, the change-over occurring at roughly the same pressure as the reversal ΔJ =±1 collision propensities. A recently proposed theoretical model involving the formation of a long-lived atom—diatomic collision complex or Feschbach resonance is invoked to explain these unusual experimental results.     

Partial synthesis of evonoloside

Conclusions The synthesis of evonoloside has been effected from cannogenol and L-rhamnose with a yield of 35%. It has been shown that when a primary alcohol group (at C₁₉) and a secondary axial hydroxy group (at C₃) are present in the aglycone, to introduce the sugar component at C₃ it is desirable first to protect the primary OH group by the partial acetylation of the aglycone.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 1, pp. 20–22, 1969     

LONG-LIVED AFTERGLOW OF PHOTOSYNTHETIC PIGMENTS IN SOLUTION: PHOTOCHEMILUMINESCENCE

Abstract —Our recent research on photochemiluminescence (PCL) of pigments in solutions is reviewed. PCL was observed in the course of photooxidation by oxygen of chlorophyll a , bacteriochlorophyll, protochlorophyll, their analogs, synthetic dyes and aromatic hydrocarbons. The PCL of chlorophyll was studied in detail. It depends on oxygen concentration, intensity of exciting light, pH, nature of pigments, solvents etc. The thermochemiluminescence was observed after illumination of liquid and solid pigment solutions at low temperature (down to - 170C). The excitation spectra of PCL coincide with the pigment absorption spectra. The PCL emission spectra in most cases differ from those of pigment fluorescence. Electron acceptors, electron donors, radical inhibitors and β-carotene quench PCL. The quenching efficiency of electron acceptors is similar to their action on the chlorophyll triplet state. The quenching effect of radical inhibitors and β-carotene correlates with their activity in reaction with singlet oxygen. The effect of quenchers on the chlorophyll fluorescence, photobleaching and pigment sensitized oxygenation was studied. Analysis of experimental data allowed the assumption that chemiluminescence accompanies the decomposition of labile pigment peroxides. The accumulation of peroxides is probably due to the reaction in the complex of pigment and singlet oxygen, formed as a result of energy transfer from photoexcited (triplet) pigment molecules to oxygen. The terminal chemiluminescence emission proceeds from the singlet excited states of molecules of pigments and products of their oxidation.