Etude de la chloration du polychlorure de vinyle en fonction de sa tacticite

Polyvinyl chloride samples of various tacticity have been prepared and photochlorinated in CCl₄ for 4 hr. The chlorination degree correlates directly with the degree of syndiotacticity. Initial PVC with syndiotacticity about 56 per cent, which can be regarded as alternate sequences of syndiotactic and isotactic diads, is quickly chlorinated. The mechanism of chlorine attack on the macromolecula is directly connected with the stereoregularity.     

Coulometric titration of acids in non-aqueous solvents

Coulometric titrations of mineral acids, sulphonic acids, carboxylic acids, enols, imides and phenols have been carried out in t-butanol or in acetone with electrically generated tetrabutylammonium hydroxide. Either a potentiometric titration or a visual indicator end-point may be used. The amount of acid titrated ranges from 10 to 60 muequiv, and the precision and accuracy of the method are excellent.     

Nitration of Durene and Pentamethylbenzene with Nitronium Salts in Nitromethane and Acetonitrile

Nature and proportions of the products formed in the nitrations mentioned in the title are affected by the process of mixing. Pentamethylnitrobenzene, formed initially in the nitration of pentamethylbenzene, is attacked by a nitronium ion at a position meta to the nitro-group. In the σ-complex formed, loss of a proton from a methyl group leads to production of by-products and release of nitrite ions. The nitrous acid formed is protonated, and water is displaced from the nitrous acidium ion by the anion, PF₆^?, giving the nitrosonium ion which forms a 1:1 symmetric molecular complex with pentamethylbenzene. A similar complex is formed in the reaction between durene and nitronium salts. The results are consistent with the view that no σ-bond is formed between the aromatic compound and the nitrosonium ion.     

Kryoskopische Bestimmung der Aktivitätskoeffizienten von Nichtelektrolytmischungen

Zusammenfassung Es wurde eine Methode entwickelt, welche die Aufnahme von Schmelzkurven von binären Nichtelektrolytmischungen mit einer Genauigkeit von 0,001° (und dementsprechend von etwa 0,00001 im Molenbruch) gestattet. Die Bestimmung der Schmelzpunkte erfolgte an Hand von Erwärmungskurven, die bei konstanter Wärmezufuhr mit einem Thermistor aufgenommen wurden.Die Methode wurde auf die Systeme 1,2,4-Trichlorbenzol-(1)-n-Hexan und Anilin-(1)-Cyclohexan angewendet und sollte hier der Überprüfung und Ergänzung der Daten dienen, die früher aus Dampfdruckmessungen¹ und Messungen der Löslichkeitskurve² abgeleitet wurden. Die Übereinstimmung mit den früheren Resultaten ist bei dem System Trichlorbenzol-Hexan ausgezeichnet, bei dem System Anilin-Cyclohexan annehmbar. Die nun genauer zu bestimmenden lnf ₁/x ₂ ² -Kurven (f _i Aktivitätskoeffizient,x _i Molenbruch der Komponentei) zeigen bei dem Übergang von verdünnter zu konzentrierterer Lösung eine plötzliche Änderung, als ob mit Erhöhung der Konzentration der Komponente 2 eine plötzliche Änderung der molekularen Struktur der Lösung einherginge. Dieser Befund steht zwar mit früheren Beobachtungen^1,2 in qualitativer Übereinstimmung, konnte aber bisher nicht so scharf formuliert werden.Mit 11 AbbildungenAuszugsweise vorgetragen auf der Chemiedozententagung der Chemischen Gesellschaft der Deutschen Demokratischen Republik in Halle (Saale) 24.–26. Juni 1959.     

Basische Metalle. LXIV. Lewis-basische Bis(trimethylphosphan)cobalt-Komplexe mit Indenyl und Trifluormethylcyclopentadienyl als Liganden

Basic Metals. LXIV. Lewis-basic Bis(trimethylphosphine)cobalt Complexes with Indenyl and Trifluormethylcyclopentadienyl as Ligands The half-sandwich type compounds C₉H₇Co(PMe₃)₂ ( 1 ) and (C₅H₄CF₃)Co(PMe₃)₂ ( 6 ) are prepared from CoCl(PMe₃)₃ and C₉H₇Li or TlC₅H₄CF₃, respectively. They behave like metal bases and react with HBF₄, CH₃I (or CF₃SO₃CH₃), I₂, and CH₃COCl by oxidative addition to give the cationic complexes [C₉H₇CoX(PMe₃)₂]⁺ and [(C₅H₄CF₃)CoX(PMe₃)₂]⁺ (X ? H, CH₃, I, COCH₃) which are isolated as the PF₆ salts ( 2–5 and 7–10 ). The ¹HNMR and the IR spectra of the compounds 1–10 are discussed, also in comparison to those of the corresponding cyclopentadienylcobalt complexes.     

Identification of a series of C25-C40 acyclic isoprenoid hydrocarbons in crude oils

The identification of acyclic isoprenoid hydrocarbons in organic extracts of geological samples and particularly in petroleum deserves a great interest from the biological origin of the sedimentary organic matter and the understanding of geochemical processes.     

STRUCTURE AND PHOTOBIOLOGICAL ACTIVITY OF 7-CHLORO-1,4-BENZODIAZEPINES. STUDIES ON THE PHOTOTOXIC EFFECTS OF CHLORDIAZEPOXIDE, DESMETHYLCHLORDIAZEPOXIDE AND DEMOXEPAM USING A BACTERIAL INDICATOR SYSTEM

The photobiological activity of chlordiazepoxide, an active ingredient of the drug Librium, which is known to induce phototoxic effects, and two of its metabolites, desmethylchlordiazepoxide and demoxepam, was investigated. Upon irradiation of these biologically active compounds with longwave UV light, the main decomposition product formed is an oxaziridine. Using a strain of Salmonella typhimurium as a test organism for cytotoxicity, it could be demonstrated that not only the drug itself, but also the major mammalian metabolites are phototoxic and, furthermore, that the respective oxaziridines are responsible for the toxic effects found upon irradiation. A close relationship appears to exist between the phototoxicity of the nitrones and the toxicity in the dark of their respective oxaziridines. Investigations of the photobiological activity of a few closely structurally related benzodiazepines could establish that a 4-oxide moiety in the benzodiazepine nucleus is the structural characteristic responsible for the appearance of phototoxicity; in those compounds which contain a 4-oxide in the benzodiazepine nucleus, photo-decomposition to a toxic oxaziridine is observed, while the analogues lacking the 4-oxide moiety do not show this characteristic and, therefore, no phototoxic effects can be observed. Finally, mutagenicity tests performed with the same bacterial indicator as used for phototoxic studies, and including chlorpromazine as a positive reference compound, indicate that under the present experimental conditions photoproducts formed upon irradiation of chlordiazepoxide and its metabolites with longwave UV light do not exert a mutagenic effect.     

Structure and Vibrational Spectra of 1:1 Chloranilic Acid (CLA)—Tetramethylpyrazine (TMP) Complex

In searching for new molecular materials the crystals of 1:1 complexes of tetramethylpyrazine (TMP) with chloranilic acid (CLA) were grown. In the crystalline lattice of TMP.CLA infinite chains of hydrogen bonded components are formed. Very strong (d_(O·sN) = 2.692(2) {?}) hydrogen bonds without proton transfer are present. The components of the complex form stacks of parallel arrangement with the distance typical of van der Waals interaction. One can conclude that in packing, interactions via hydrogen bonds play a decisive role. In the IR spectrum one observes a broad, continuous absorption with well resolved trio typical of strong hydrogen bonds. A detailed analysis of IR and Raman spectra in the low frequency region related to deformation vibrations of CH₃ groups shows that strong interaction via hydrogen bonding only slightly affects the dynamics of these groups.