Cyclopolycondensations. VII. Preparation of aromatic poly(ureido acids) by the low-temperature solution polymerization and cyclodehydration to fully aromatic polyquinazolinediones

Fully aromatic polyquinazolinediones (IV) of high molecular weight were obtained by thermal cyclodehydration of aromatic poly(uredio acids) (III) prepared by the polyaddition reaction of 4,4′-diaminobiphenyl-3,3′-dicarboxylic acid (I) with aromatic diisocyanates (II). From the kinetic study of reactions of model systems (anthranilic acid with phenyl isocyanate) in the presence of a variety of basic catalysts, it was established that tertiary amines had the highest catalytic activity for the formation of ureido linkage. The optimum polymerization conditions were determined by the study of reaction variables such as monomer concentration, polymerization temperature, monomer ratio, and catalyst concentration. The effect of polarity and purity of organic solvents and reactants was also studied.     

Preparation and characterization of silicalite-1 membranes prepared by secondary growth of seeds with different crystal sizes

MFI-type zeolite particles of 0.1–1 μm in diameter were prepared by adjusting tetra-n-propylammonium hydroxide (TPAOH) and water contents in synthesis mixtures. Using those particles as seeds, MFI-type zeolite membranes were prepared on the surface of a porous mullite tube by secondary growth. The membranes were formed as polycrystalline zeolite layers on and inside the porous support, and the membranes were composed of the [h 0 h]-oriented crystallites. The membrane consisting of a-oriented crystallites could be also prepared. However, the a-oriented zeolite layers were not active on the permeation properties of butanes. Rather the size and loaded amount of the seed particles influenced on the permeation properties through the membranes. As a result, the n-C₄H₁₀/i-C₄H₁₀ permselectivity could be increased to 220 by adjusting the size and the loaded amount of particles. These results suggest that the number of loaded particles affects on the permeation properties through the membranes.     

Formation of M+. ions under matrix fast atom bombardment conditions: Does charge exchange reaction occur?

The formation of molecular ions, M^+., under fast atom bombardment (FAB) conditions using a liquid matrix was examined by using a new type of synthesized compounds in which preferential M^+. peaks appear in their FAB spectra. The FAB spectra were compared with the corresponding mass spectra obtained by the electron impact (EI) ionization, chemical ionization (CI) and charge-exchange ionization (CEI) methods. All of the spectra showed preferential peaks of M^+. ion and a characteristic intense fragment ion peak originating from a β-fission. The FAB spectra were similar in the fragment ions appearing in the EI spectra and were very similar in the fragmentation pattern to the CEI spectra using Ar^+. and Xe^+. as the reagent ions. Further, the FAB spectra did not show any doubly charged ion peaks, while the 70 eV EI spectra showed the peaks of doubly charged molecular and/or fragment ions. The isobutane CI spectra of the synthesized compounds suggested that the formation of M^+. ions occurred through the CE reaction with isobutane ion, C₄H₁₀^+., and the CI spectra showed a marked intense fragment ion peak originating from the β-fission which seemed to occur characteristically in CEI processes. The results obtained suggested that the formation of M^+. ions under matrix FAB conditions occurred mainly by CE reactions between the analytes M and matrix molecular ions B^+. and/or fragment ions b^+..     

Distribution and behavior of long-lived radioiodine in soil

The concentration of¹²⁹I in soil in Japan was determined by neutron activation analysis. For the activation analysis, pre-irradiation chemical separation of the iodine was carried out by acid decomposition and distillation and post-irradiation treatment was performed by ion exchange and solvent extraction. The concentration of stable iodine and¹³⁷Cs were also determined and compared with the behavior of¹²⁹I in soil.Soil samples from Ibaraki, Fukui, Fukushima, and Nagasaki Prefectures were analyzed and¹²⁹I was detected in amounts ranging from 10^–7 to 10^–5 Bq/g soil in uncultivated surface soil. There are apparently small variations in the¹²⁹I concentrations in each of the regions analyzed.From depth profile studies in sandy soil, the iodide form of¹²⁹I was found to migrate downward at a relatively rapid rate while other species remain longer in the surface soil.     

Charge-transfer interactions,exciplex formations and ionic dissociations in singlet oxygen reactions

Intermolecular perturbation and configuration interaction calculations have been carried out to elucidate the attacking modes of singlet molecular oxygen (¹O₂) to allyl olefins and electron-rich olefins, which are classified into four groups from their molecular structures. It is found: (1) that the attacking modes are dependent on the molecular structure of substrates ; (2) that the charge-transfer (CT) interactions between ¹O₂ and substrates are particularly important for the formation of exciplexes through which the ene and (2+2) reactions of ¹O₂ proceed ; and (3) that the CT energy levels are important in governing the fraction of ionic dissociation to produce Superoxide anion and the relative ratio between the (4+2) and (2+2) reactions of ¹O₂ with dienes, heterocycles and related species.     

Solvents inducing oxidation of hydroxylamines

Hydroxylamines gradually undergo oxidation to their oximes on being dissolved in organic solvent (e.g. methanol). This phenomenon was followed by (1)H-NMR and liquid chromatography-mass spectrometry (LC-MS). The oxidation rate was estimated from the peak area observed on the mass chromatogram at the protonated molecule or fragment ion on LC-atmospheric pressure chemical ionization (APCI)-MS. The results showed that the oxidation rate of hydroxylamines depended on the solvent type.     

Absorption and fluorescence of a nonionic detergent in aqueous solution

The absorption and fluorescence spectra of a detergent, polyoxyethylene octylphenyl ether, were measured in water at different concentrations. The absorption spectra had a peak at 275 mμ and a shoulder at 281 mμ. The spectra were independent of concentration below the critical micelle concentration, but the molar extinction coefficients of the peak and the shoulder increased with concentration above the critical micelle concentration. The critical micelle concentration value derived from the absorption data was in good agreement with those obtained by other methods. The fluorescence spectra of the detergent in water were independent of concentration in dilute solutions, if the intensities of the spectra were normalized at the peak at 302 mμ. At higher concentrations, a weak excimer band appeared at 345 mμ, whose intensity increased with concentration. The excimer band manifested itself at a concentration slightly lower than the critical micelle concentration. The main band decreased and the excimer band increased, as the temperature was raised. An excimer band was observed in the same region of the spectra for the pure detergent, either in the solid or liquid state. The equilibrium solid spectra exhibited a very strong excimer emission. It was concluded that the excimers were formed within micelles in the case of aqueous solutions.     

Amphiphilic block copolymers of vinyl ethers by living cationic polymerization. II. Synthesis and surface activity of macromolecular amphiphiles with pendant amino groups

Amphiphilic block polymers of vinyl ethers (VEs). $\rlap{--} [{\rm CH}_{\rm 2} {\rm CH}\left( {{\rm OCH}_{\rm 2} {\rm CH}_{\rm 2} {\rm NH}_{\rm 2} } \right)\rlap{--} ]_m \rlap{--} [{\rm CH}_{\rm 2} {\rm CH}\left( {{\rm OR}} \right)\rlap{--} ]_n \left( {{\rm R: }n{\rm - C}_{{\rm 16}} {\rm H}_{{\rm 33}} ,{\rm }n{\rm - C}_{\rm 4} {\rm H}_{\rm 9} ;m \simeq 40,{\rm n} = 1 - 10} \right)$ were prepared, each of which consists of a hydrophilic segment with pendant primary amino groups and a hydrophobic poly(alkyl VE) segment. Their precursors were obtained by the HI/I₂-initiated sequential living cationic polymerization of an alkyl VE and a VE with a phthalimide pendant (CH₂ = CHOCH₂CH₂Im; Im; phthalimide group), where the segment molecular weights and compositions (m/n ratio) could be controlled by regulating the feed ratio of two monomers and the concentration of hydrogen iodide. Hydrazinolysis of the imide functions gave the target polymers which were readily soluble in water under neutral conditions at room temperature. These amphiphilic block polymers lowered the surface tension of their aqueous solutions (0.1 wt%, 25°C) to a minimum ? 30 dyn/cm when the hydrophobic pendant R was n-C₄H₉ (n = 4–9). The polymers with n-C₄H₉ pendants in the hydrophobic segment exhibited a higher surface activity than those with n-C₁₆ H₃₃ pendants. The surface activity of the polymers also depended on the pH of the polymer solutions; the surface activity increased in more basic solutions where the ionization of the amino group (? NH₂)2? NH₃^⊕) is suppressed.     

A stable silicon congener of highly strained bicyclo[3.2.0]hepta-1,3,6-triene

A silicon-containing fused bicyclic compound with a highly strained bridgehead double bond, 2,3,6,7-tetra-tert-butyl-4-(tert-butyldimethylsilyl)-5-(tert-butyldimethylsiloxy)-5-silabicyclo[3.2.0]hepta-1,3,6-triene (2), was synthesized quantitatively by the reaction of 1,2-bis-tert-butyl-4,4-bis(tert-butyldimethylsilyl)-4-silatriafulvene (3) with di-tert-butylcyclopropenone (4) at 80 degrees C. An X-ray crystallographic analysis for 2 not only confirmed a bicyclic structure having a silacyclopentadiene (silole) ring fused with a silacyclobutene ring but also the remarkable deformation around the double bonds; the sum of the bond angles around the unsaturated bridgehead carbon was 333 degrees . The strain energy of a model 5-silabicyclo[3.2.0]hepta-1,3,6-triene was calculated at the MP2/6-31+G(d,p)//B3LYP/6-31+G(d) level (30.2 kcal/mol) to be comparable to that for parent bicyclo[3.2.0]hepta-1,3,6-triene (30.7 kcal/mol). Despite the high steric strain, 2 was stable enough to be kept intact for several months in the air. The high stability is ascribed to the effective steric protection of the ring system by the bulky substituents.     

Analysis of scintigrams using fuzzy theory

Textural features for phantom images were extracted. Texture parameters which represent RI distribution--skew, energy, entropy and angular second moment were used. But, it was difficult to analyse the images using discriminant analysis for textural features, because textural features had statistical noise. Therefore fuzzy reasoning was adapted to analyse the images. Textural features for six kinds of images were showed using membership function. The possibility to the image was evaluated using the value of membership function on each images. Fuzzy reasoning could be done easily using max-min composition formula. The reasoning was found more suitable to analyse the images than discriminant analysis and will be considered useful for analysis of clinical scintigrams.