Ueber Systeme partieller Differentialgleichungen erster Ordnung

Ohne Zusammenfassung     

Enantiomer-Differentiation Induced by an Enantiomeric Excess during Chromatography with Achiral Phases

It is shown, in the case of the diketone 2 , that chromatography with achiral phases of a non-racemic mixture of enantiomers can furnish fractions which differ in enantiomeric excess. Such chromatography may, therefore, be used to further enrich a sample in one enantiomer. By the same token, chromatography is not a generally safe method for the purification of the product of an enantio-differentiating process, if the enantiomeric excess of a purified portion of that product is taken to be a measure of the efficiency of the process. The described effect represents an enantiomer differentiation induced solely by an alredy existing enantiomeric excess during chromatography. It thus belongs to a class of effects where the relative amounts of two enantiomers induce an observable difference between them. Such effects are called EE effects. The common principle underlying EE effects is explained by a simple symmetry argument. Since EE effects can also occur during reactions with achiral reagents, further transformations of an enantiomer-enriched product may furnish false information on its enantiomeric excess.     

New Synthetic Routes to β-Olefinic Trialkoxyphosphonium Salts and Phosphonates: Organometallic Variants of the Michaelis-Arbuzov Reaction

The low-temperature addition of tertiary phosphites to [(allyl)Fe (CO)₄]⁺X^? complexes proceeds regio- and stereospecifically and produces metal-coordinated β-olefinic trialkoxyphosphonium ions. These can be converted by various routes into the uncomplexed phosphonium salts or phosphonates. Similar reactions of acyclic [(dienyl)Fe(CO)₃]⁺X^? compounds give metal-coordinated (2,4-dien-1-yl)trialkoxyphosphonium salts or dialkyl (2,4-dien-1-yl)phosphonates. The mechanisms and their relationship to the classical Michaelis-Arbuzov reaction are discussed. The new compounds are characterized, if possible, by ¹H-, ¹³C-, and ³¹P-NMR spectra. The new phosphonium salts and phosphonates, potentially useful for Wittig-Horner reactions, are difficult to obtain by conventional routes.     

Heat capacities of liquids linear aliphatic polyoxides

Heat capacities at constant pressure of liquid polyoxymethylene (430-540 K) and polyoxyethylene (330-430 K) have been measured by scanning calorimetry. These new data are discussed together with the heat capacity of polyethylene and other linear, aliphatic polyoxides to arrive at a wide-range addition scheme for heat capacities. Values of absolute entropy, enthalpy, and Gibbs free energy are estimated. The new data are offered as “Recommended Data 1984” in our ATHAS Data Bank.     

Eine bequeme und vielseitige synthese von 13-thia-carbacyclinen

A versatile and convenient large scale synthesis of 13-thiacarbacyclins is reported.     

The lifetime of the 266 keV level in 206Tl

The lifetime of the ²⁰⁶Tl 2^? state at 266 keV has been measured by the delayed coincidence technique. The state was populated via the γ-decay of high-lying states excited in the ²⁰⁵Tl (d, p)²⁰⁶Tl reaction at E_d = 9.0 MeV. Delayed coincidences between a Si surface-barrier detector and a Ge(Li) detector resulted in a mean life for the 266 keV level of τ = 3.3(2) ns. The deduced B(E2) value of 171 (11) e² · fm⁴ indicates strong configuration mixing of two-hole states in this level.