Influence of organic modifiers on morphology and crystallization of poly(ϵ‐caprolactone)/synthetic clay intercalated nanocomposites

ε‐caprolactone was polymerized in the presence of neat montmorillonite or organomontmorillonites to obtain a variety of poly(ε‐caprolactone) (PCL)‐based systems loaded with 10 wt % of the silicates. The materials were thoroughly investigated by different X‐ray scattering techniques to determine factors affecting structure of the systems. For one of the nanocomposites it was found that varying the temperature in the range corresponding to crystallization of PCL causes reversible changes in the interlayer distance of the organoclay. Extensive experimental and literature studies on this phenomenon provided clues indicating that this effect might be a result of two‐dimensional ordering of PCL chains inside the galleries of the silicate. Small angle X‐ray scattering and wide angle X‐ray scattering investigation of filaments oriented above melting point of PCL revealed that polymer lamellae were oriented perpendicularly to particles of unmodified silicate, while in PCL/organoclay systems they were found parallel to clay tactoids. Calorimetric and microscopic studies shown that clay particles are effective nucleating agents. In the nanocomposites, PCL crystallized 20‐fold faster than in the neat polymer. The crystallization rate in nanocomposites was also significantly higher than in microcomposite. Further research provided an insight how the presence of the filler affects crystalline fraction and spherulitic structure of the polymer matrix in the investigated systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2350–2367, 2007     

The convenient route to cd fragment for the synthesis of vitamin D3 relatives

The efficient degradation of $\text{1}$ to the α-methylene ketone $\text{4}$ is described. Compound $\text{4}$ was then converted to the allylic alcohol $\text{8a}$ - the precursor of vitamin D³ relatives.     

Ein Computerverfahren für die Massenspektrometrische Untersuchung Organischer Proben bei Fraktionierter Direktverdampfung

A procedure is described for use of an on-line digital computer to acquire and process low resolution mass spectra obtained by a fractionated evaporation technique. The procedure generates unambiguous spectra from uniform solid or liquid organic substances, and characteristic spectra from multicomponent organic solid or liquid samples. The system is realised with minimal hardware configuration.     

N-Vinyl as N-H protecting group. Synthesis of cyclic imines from N-vinyllactams and organolithium reagents

On reaction with organolithium reagents followed by hydrolysis and distillation, N-vinylpyrrolidone ( 1 ) gives five-membered ring imines 3-8 , whereas N-vinylcaprolactam ( 2 ) gives mixtures of seven-membered ring imines and the corresponding ∈-amino ketones.     

Conformational equilibria and photoinduced tautomerization in 2-(2′-pyridyl)pyrrole

Depending on the polarity and protic abilities of the solvent, 2-(2′-pyridyl)pyrrole can exist in either syn or anti rotameric forms. In nonpolar solvents, intramolecular excited state single proton transfer is observed, manifested by the appearance of low-energy tautomeric emission. The solvent-assisted excited state double proton transfer reaction is also detected. DFT calculations confirm low barriers for both single and double proton transfer processes in the lowest excited singlet state and show different character of the tautomerization in both cases: in the intramolecular reaction, mutual approach of two nitrogen atoms plays an important role.     

Circular dichroism of 9,10-dihydrophenanthrene derivatives reveals both the absolute configuration and conformation: a novel approach to Mislow's helicity rule

The absolute configuration and the conformation of 9,10-trans-disubstituted 9,10-dihydrophenanthrenes, known chiral metabolites of phenanthrene-9,10-oxide, have been determined by circular dichroism. The absolute configuration assignment is based on the sign of the long-wavelength Cotton effect (A-band), which is conformation invariant and originates from benzylic chirality. This provides a new interpretation of the Mislow biphenyl-helicity rule for the case of the 9,10-dihydrophenanthrene chromophore. The sign of the B-band Cotton effect reflects the conformation of the biphenyl chromophore in 9,10-dihydrophenanthrenes. It is shown that the origin of chiroptical properties of 9,10-dihydrophenanthrenes is closely related to those of 5,6-trans-disubstituted 1,3-cyclohexadienes.     

Electronic structure and spectra of organic molecules

The Pariser-Parr-Pople method is used to predict the singlet-singlet ( ^* type). Electronic transition energies for the anions of hydroxy derivatives of benzene, pyridine and pyrimidine. The core integral for the -O^– substituent was treated as an empirical parameter and its value was chosen to fit results for the phenoxide ion and then applied for the compounds with the -O^– substituents. The results of the calculations for molecules with the -O^– groups are compared with those of the corresponding molecules containing the -OH and -NH₂ substituents as well as with the experimental data. No serious deviations between theoretical and experimental data other than those which could be ascribed to steric hindrances occuring in the molecules were found.

---

Zusammenfassung Die Pariser-Parr-Pople-Methode wird benutzt, um die Singlett-Singlett-Übergangsenergien (- ^*-Typ) von Benzol-, Pyridin- und Pyrimidinderivaten zu berechnen, die OH-Gruppen enthalten. Das Rumpfintegral des -O^–-Substituenten wurde wie ein empirischer Parameter behandelt. Sein Wert wurde so gewählt, daß er die Meßergebnisse für das Phenolat-Anion richtig wiedergibt. Die Resultate der Berechnungen für Moleküle mit der -O^–-Gruppe werden mit denjenigen für die entsprechenden Moleküle mit OH- und NH₂-Substituenten als auch mit den experimentellen Daten verglichen. Es werden keine ernsten Abweihungen zwischen theoretischen und experimentellen Daten gefunden, außer solchen, die einer sterischen Hinderung zugeschrieben werden können.

---

Résumé La méthode de Pariser, Parr et Pople est utilisée pour prédire les transitions électroniques ( ^*) pour les formes anioniques des derivés hydroxy du benzène, pyridine et pyrimidine. La valeur d'integrale de coeur associée du substituant -O^– a été choisie de façon à reproduire les positions des bandes d'absorption de forme anionique du phenol et après elle a été appliquée pour les composés envisagés. Les resultats des calculs pour l'anions sont mis en comparaison avec les resultats obtenus pour les correspondantes derivés aminés et hydroxy et avec les donnés experimentales. Peu de déviations ont été obtenus, en dehors de ceux que l'on peut attribuer à des encombres steriques.

---

---

Based in part on a M. Sci. thesis by M. Berndt, N. Copernikus University, Toru, 1969 (unpublished, in Polish).     

Unusual solid-state conformation of D-glucitol hexa(p-chlorobenzoate)

The carbon atom chain in the molecule ofd-glucitol hexa (p-chlorobenzoate) adopts a planar, zigzag conformation in the solid state, as determined by X-ray crystallography. The preference for such conformation in the crystal can be ascribed to the stacking interactions in which an infinite number of p-chlorobenzoyloxy substituents is involved.