On the quantitative analysis of multicomponent mixtures by gas-liquid chromatography

Summary The thermal conductivity cell response to some heterocyclic and hydrocarbon compounds was determined relatively to pyridine and was used to calculate with accuracy the molar as well as the weight concentration of analysed multicomponent mixtures from peak area values. From these and other results obtained by correcting data that have been previously reported in literature it was shown that by applying the appropriate factor it was possible to obtain the composition of the unknown mixture either as the mole or the weight per cent with accuracy.

---

Zusammenfassung Das Ansprechen der Wärmeleitfähigkeitszelle auf einige heterocyclische Verbindungen und Kohlenwasserstoffe wurde gemessen (bezogen auf Pyridin) und zur Berechnung der Zusammensetzung von Mischungen mehrerer Komponenten aus den Peak-Flächenwerten benutzt. Es wurde gezeigt, daß man bei Verwendung eines geeigneten Faktors die Zusammensetzung einer unbekannten Mischung in Mol-% oder Gew.-% genau errechnen kann.

     

Molecular structure matching by simulated annealing. II. An exploration of the evolution of configuration landscape problems

Summary This paper considers some of the landscape problems encountered in matching molecules by simulated annealing. Although the method is in theory ergodic, the global minimum in the objective function is not always encountered. Factors inherent in the molecular data that lead the trajectory of the minimization away from its optimal route are analysed. Segments comprised of the C atoms of dihydrofolate reductase are used as test data. The evolution of a reverse ordering landscape problem is examined in detail. Where such patterns in the data could lead to incorrect matches, the problem can in part be circumvented by assigning an initial random ordering to the molecules.     

Benzo[b]thiophene mit Halogensubstitution in 5-Stellung

Zusammenfassung Cyclisierung von -(p-Chlor-phenylthio)-acetessigester und -(p-Brom-phenylthio)-acetessigester mit Polyphosphorsäure und anschließende Hydrolyse gab 5-Chlor- und 5-Brom-benzo[b]-thiophen-3-essigsäure. Deren Säurechloride wurden mit verschiedenen sekundären Aminen zu den entsprechenden N-substituierten 5-Chlor-und 5-Brom-benzo[b]thiophen-3-acetamiden umgesetzt. Diese wurden mit LiAlH₄ zu den tertiären Aminen reduziert.Ähnlich wie im Fall des -(p-Methoxy-phenylthio)-acetessigesters konnte auch die entsprechende Fluorverbindung nicht zu einem Benzo[b]thiophen-Derivat ringgeschlossen werden.

---

Cyclization reactions of -(p-chloro-phenylthio)-acetoacetate and -(p-bromo-phenylthio)-acetoacetate withPPA followed by hydrolysis gave 5-chloro- and 5-bromobenzo[b]thiopheneacetic acid. The acid chlorides reacted with various secondary amines to give the corresponding N-substituted 5-chloro- and 5-bromo-benzo[b]thiophene-3-acetamides. These were reduced by LiAlH₄ to tertiary amines.Similar to -(p-methoxy-phenylthio)-acetoacetate the fluoro compound gave no cyclization to a benzo[b]thiophene derivative.

---

---

Mit 1 Abbildung     

Dielectric behaviour in Ni0.65Zn0.35CuxFe2.xO4 ferrites

A series of samples of the type Ni_0.65Zn_0.35Cu_xFe_2–xO₄ (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) were prepared by means of a ceramic technique. The existence of a single phase was confirmed in X-ray studies. The dielectric constantK and dielectric lossD were measured at different temperatures at a frequency of 1 kHz. The pronounced increase in the dielectric constant at the transition temperature is due to the phase transformation from the ferrimagnetic to the paramagnetic state. The decrease in the dielectric loss with temperature is due to the reduction in the relaxation time of the hopping electrons and holes. The Tawfik constant was calculated in the ferrimagnetic state and was found to be correlated to the dielectric constant.

---

Zusammenfassung Mittels einer Keramiktechnik wurde eine Reihe von Proben des Types Ni_0.65Zn_0.35Cu_xFe_2–xO₄ mitx=0, 0.1, 0.2, 0.3, 0.4 und 0.5 hergestellt. In Röntgendiffraktionsuntersuchungen wurde die Existenz von Single-Phasen bestätigt. Bei verschiedenen Temperaturen und einer Frequenz von 1 kHz wurde die DielektrizitätskonstanteK und der dielektrische VerlustD gemessen. Die ausgesprochene Erhöhung der Dielektrizitäts-konstante bei der Umwandlungstemperatur kann der Phasenumwandlung vom ferromagnetischen in den paramagnetischen Zustand zugeschrieben werden. Die Abnahme des elektrischen Verlustes mit steigender Temperatur kann durch kleinere Relaxationszeiten der springenden Elektronen und Löcher erklärt werden. Für den ferromagnetischen Zustand wurde auch die Tawfik-Konstante berechnet, die in Korrelation mit der Dielektrizitäts-konstante gefunden wurde.

     

Valency stabilization of polyvalent ions during gamma irradiation of their aqueous solutions by sacrifical protection

Polyvalent ions are very sensitive to gamma irradiation in aqueous solutions. The present work is a part of a more comprehensive study dealing with the stabilization of certain oxidation states of some polyvalent ions during their gamma irradiation in aqueous systems. Sulphite ions, being well known reducing agents has been used for stabilizing Fe(II) ions in aqueous solutions during gamma radiolysis. Fe(II) ions in solution are known to be readily oxidized by gamma radiations in such a way that a 10^–3N solution decays completely in about 2 hours at a dose rate 310 Gy/hr. In presence of an excess of sulphite ions it was found that Fe(II) ions were stabilized for extended time periods depending on the amount of sulphite ions used. The conditions of stabilization and its limits in the studied case has been identified.     

Macromolecular engineering of polylactones and polylactides. XV. Poly(D,L)-lactide macromonomers as precursors of biocompatible graft copolymers and bioerodible gels

The functional aluminum alkoxide, Et₂Al? O? (CH₂)₂? O-C(O)? C(CH₃)?CH₂, is a very effective initiator for the (D ,L )-lactide (LA) polymerization in toluene at 707deg;C. The coordination-insertion type of polymerization is living and exclusively yields linear P (D ,L )-lactide macromonomers of a predictable molecular weight and a narrow molecular weight distribution. IR and ¹H-NMR studies show that the methacryloyl group of the initiator is selectively and quantitatively attached to one chain end, whereas the second extremity is systematically a hydroxyl function resulting from the hydrolysis of the living growing site. α,ω-Dimethacryloyl-P(D ,L )-lactides, i.e., α,ω-macromonomers, have also been successfully synthesized by the additional control of the termination step, i.e., by reaction of Al alkoxide end groups with methacryloyl chloride. α-Macromonomer and α,ω-macromonomer P(D ,L )-lactides are easily free-radical copolymerized with 2-hydroxyethyl methacrylate (HEMA), resulting in a hydrophilic poly (HEMA) backbone grafted with hydrophobic P(D ,L )-lactide subchains and a biodegradable amphiphilic network, respectively. © 1994 John Wiley & Sons, Inc.     

Computerized GC/MS detection of monoaromatic and triaromatic steroid hydrocarbons in Alamein crude oil

Series of C-ring monoaromatic steroid hydrocarbons (C₂₁, C₂₂, C₂₇ ? C₂₉) and triaromatic steroid hydrocarbons (C₂₀, C₂₁, C₂₆ ? C₂₈) have been recognized in the aromatic hydrocarbon fraction of Alamein crude oil from the western desert, Egypt. Detection of these compounds were based on mass fragmentography of the key ions m/z 253 and m/z 231 and comparison of the mass spectra and relative retention times with literature data. The predominance of the C₂₉ monoaromatic steroids and C₂₈ triaromatic steroids provide further evidence for a land plant origin of Alamein oil. The results substantiate previous evidence of the occurrence of an aromatization process with increasing maturation and indicate a moderate maturity level for Alamein oil.