Photoreduction de la benzophenone par des phtalimidines et des dihydro isoquinolones: Etude chimique par RMN PNIC

Benzophenone is photoreduced by pthalimidines and dihydro isoquinolones. The hydrogen atom α to the nitrogen atom is abstracted and radical coupling leads to adducts. CIDNP studies of these adducts show inversion of polarisation for the adduct on the N-alkyl chain when the nitrogen is bound to a benzylic methylene. This inversion is explained by considering that the radical on the N-alkyl chain derives from the radical on the ring.     

Benzophenone photoreduction by heteroatom-containing donors

Nanosecond flash photolysis has been carried out on benzophenone solutions in benzene and acetonitrile in presence of oxygen- and sulfur-containing reductants such as anisole, thioanisole, dibutyl sulfide and methyl 2-octyl ether. The quantum yield of ketyl formation is compared to previous results on the quantum yields of the final benzophenone disappearance. This comparison is also related to previous data on benzophenone reduction by nitrogen-containing reductants such as amines and amides and suggests a general mechanism for benzophenone photoreduction by heteroatom-containing donors.     

Etude de la cristallinite de derives n-octadecyliques de l'alcool polyvinylique obtenus par greffage chimique

Differential scanning calorimetry has been used to study the heats of fusion and melting transitions of n-octadecyl derivatives of polyvinyl alcohol. These derivatives were obtained by grafting paraffinic chains on polyvinyl alcohol, at various proportions. The melting transitions are independent of the degree of substitution; the heats of fusion are proportional to the fraction of crystallizable units. Using Flory's equilibrium crystallization theory, it is possible to interpret these results assuming, as demonstrated previously, that the chemical grafting is sequential with two unreacted hydroxyl groups between two adjacent paraffinic side-chains.     

Synthesis of 2,6-Dihalo-4-nitro-N-alkylanilines by Aromatic Substitution of 2,6-Dihalo-4-nitro-arylethers

An aromatic nucleophilic substitution reaction of phenylethers with primary amines is described. This reaction, promoted by electron-attracting groups on the benzene ring, fast and simple to perform, leads to substituted anilines in high yields.     

Synthesis of 5α, 13α, 14α-Androstan-16-One and 5α, 13β, 14β—Androstan-16-One Using a Novel 17–16 Carbonyl Transposition

In the course of current work on the conformational analysis of cis-hydrindanones¹, we required 5α, 13α, 14α and 5α, 13β, 14β-androstan-16-one 5 and 10 the C and D rings of which provide rigid models of the two conformations of cis-hydrindan-2-one.     

Oxydations par le carbonate d'argent sur celite—VII : Oxydations de diols

The oxidation of several secondary-tertiary α diols by silver carbonate on Celite is described. In the steroid series, a 17α,20α diol leads to the related ketol, whereas its 17α,20β isomer is either not affected by the reagent, or slowly cleaved to give a 17-keto steroid.     

Influence of molecular weight and molecular structure of polystyrenes on turbulent drag reduction

Summary An investigation was carried out on drag reduction of diluted solutions on nine linear polystyrenes of different molecular weight in toluene in the turbulent region (from 5,000 to 40,000 Reynolds numbers). The universal curve established byVirk et al. is only confirmed for very low concentration depending on the molecular weight and on the Reynolds number. If the maximum drag reduction varies with the molecular weight according to previous results, the intrinsic concentration shows a dependence with the cube of the molecular weight. This type of dependence explains the observed effects of the polydispersity and degradation. Moreover, no critical molecular weight below which no drag reduction occurs is observed. The study of PS samples with non-linear structure shows the total ineffectiveness of these structures giving support to the suggestion that an elongation of the polymer in the turbulent flow is responsible for the drag reduction. From the comparison between Polyox and PS properties it is concluded that both polymers have a comparable effectiveness and degradability when compared to the same DP or to the same [].

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Zusammenfassung Untersucht wurde die Verminderung des Reibungswiderstandes (VRW) verdünnter Lösungen von neun linearen Polystyrolen mit verschiedenem Molekulargewicht in Toluol im turbulenten Bereich bei Reynoldsschen Zahlen zwischen 5000 und 40000. Die vonVirk und Mitarbeitern festgestellte universelle Kurve wird nur für sehr verdünnte Lösungen, abhängig von der Reynoldsschen Zahl und dem Molekulargewicht, bestätigt. Wie schon in früheren Untersuchungen gefunden wurde, nimmt der Maximale VRW-Effekt mit dem Molekulargewicht zu, und die intrinsic-Konzentration zeigt eine Abhängigkeit mit der dritten Potenz des Molekulargewichts. Diese Abhängigkeit erklärt die beobachteten Effekte der Polydispersität und der Degradation. Weiterhin wird kein kritisches Molekulargewicht, unterhalb dessen kein VRW-Effekt auftritt, beobachtet. Die Untersuchung von nichtlinearen Polystyrolen beweist die völlige Unwirksamkeit dieser Strukturen, was den Schluß nahelegt, daß die Verlängerung des Polymers in der turbulenten Strömung für die Verringerung des Reibungswiderstandes verantwortlich ist. Durch einen Vergleich der Eigenschaften von Polyäthylenoxid und Polystyrol wird gefunden, daß beide Polymere eine vergleichbare Wirksamkeit und Degradation zeigen, wenn man Proben von gleichem Polymerisationsgrad oder gleichem Staudinger-Index [] in Beziehung setzt.

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With 9 figures and 2 tables