How is 1,1-dimethyl-1-silacy clopent-2-ene formed in the addition of dimethylsilylene to 1,3-butadiene? evidence for a pathway via a vinylsilirane intermediate

Addition of dimethylsilylene Me₂Si: to 1,4-dideutero-l,3-butadiene in gas-phaee flow pyrolysis experimenss leads to the formation of 2,5-dideutero-1, 1-dimethyl-1-silacyclopent-3-ene and 4,5-dideutero-1,1-dimethyl-1-suacyclopent-2-ene. Pyrolysis of the silacyclopent-3-ene product leads to the same silacyclopent-2-ene. This labelling pattern for the silacyclo-pent-2-ene product is compelling evidence for its formation via carbon-carbon bond-cleavage in a vinylsilirane intermediate, and for the intermediacy of the vinylsilirane in the silylene addition leading to the silacyclopent-3-ene as well.     

Experimental strategy for characterization of essential dynamical variables in oscillatory systems: effect of double-layer capacitance on the stability of electrochemical oscillators

An experimentally accessible algorithm for changing the time scale associated with a dynamical variable is proposed. In general, a differential controller can be applied to (a) identify the essential species in oscillatory systems and (b) explore their role in the feedback loops. Here, we report on classifying electrochemical oscillators by changing the time scale over which the electrode potential varies; the type of different electrochemical oscillators is identified based on whether the controlled modification of pseudo-capacitance induces or suppresses current oscillations.     

Thermal, pressure and light switchable spin-crossover materials

This article reviews the most relevant chemical and structural aspects that influence the spin-crossover phenomenon (SCO). Special attention is focussed on the recent development of SCO coordination polymers. The different approaches currently being explored in order to achieve multifunctionality in SCO materials are discussed.     

Computational studies of the thermal fragmentation of P-arylphosphiranes: have arylphosphinidenes been generated by this method?

CASSCF, CASPT2, CCSD(T), and (U)B3LYP electronic structure calculations have been performed in order to investigate the thermal fragmentation of P-phenylphosphirane (1) to phenylphosphinidene (PhP) and ethylene. The calculations show that generation of triplet PhP via a stepwise pathway is 21 kcal mol(-1) less endothermic and has a 12 kcal mol(-1) lower barrier height than concerted fragmentation of 1 to give singlet PhP. The formation of singlet PhP via a concerted pathway is predicted to be stereospecific, whereas formation of triplet PhP is predicted to occur with complete loss of stereochemistry. However, calculations on fragmentation of anti-cis-2,3-dimethyl-P-mesitylphosphirane (cis-1Me) to triplet mesitylphosphinidene (MesP) indicate that this reaction should be more stereospecific, in agreement with the experimental results of Li and Gaspar. Nevertheless, with a predicted free energy of activation of 42 kcal mol(-1), the formation of MesP from cis-1Me is not likely to have occurred in an uncatalyzed reaction at the temperatures at which this phosphirane has been pyrolyzed.     

Some experiments on γ-scattering between 122 and 145 keV at small angles

Differential cross section for scattering of 145.4 keV gamma rays by B, C, Al, Cu and Cd have been measured from 5–25°. For angles <10° it was not possible to separate Rayleigh and Compton scattering; therefore, the sum of the cross sections is given. Rayleigh cross sections have been measured for Pb at 122.1 and 136.5 keV at angles between 20° and 70°. The experimental results are compared with the form factor theory for Rayleigh scattering and the incoherent scattering factor theory for Compton scattering.     

Polypropionates from Bulla occidentalis: chemical markers and trophic relationships in cephalaspidean molluscs

A chemical investigation on the cephalaspidean Bulla occidentalis from the Gulf of Mexico led to known niuhinones A (1) and B (2) along with a new acyclic polypropionate, named niuhinone C (3). A complete NMR assignment of niuhinone A has been achieved by spectroscopic experiments, thus revising the Δ¹⁴ configuration. The occurrence of structurally related polypropionates in Bullidae species from different geographical areas is in agreement with a de novo origin in this family of molluscs and adds a further piece of evidence on prey-predator relationships among cephalaspideans.     

Über ein neues Tribromphenol,das 1-Oxy-3, 4, 5-Tribrombenzol,und ein neues Tribrom-o-Kresol,das 1-Methyl-2-Oxy-4, 5, 6-Tribrombenzol

Ohne ZusammenfassungXV. Mitteilung: M. Kohn und A. Rosenfeld, Ein Beitrag zur Kenntnis der Pseudophenole. Monatshefte f. Chemie, 1925.     

Die Einwirkung von Organomagnesiumverbindungen aufo-Phthalonitril

Ohne Zusammenfassung     

Alkalimetalle

Ohne Zusammenfassung